Work or Not. Work: Example 4. Lab Comments 6/3/2013. Work = Force X distance W = Fd W = Fdcosq

Size: px
Start display at page:

Download "Work or Not. Work: Example 4. Lab Comments 6/3/2013. Work = Force X distance W = Fd W = Fdcosq"

Transcription

1 Work = Force X distance W = Fd W = Fdcosq Unit Joules Force must be direction of motion W NET = DKE Work or Not 1. A teacher pushes against a wall until he is exhausted. 2. A book falls off the table and falls freely to the ground. 3. A waiter carried a full try of meals across the room. 4. A rocket accelerates through space. Mr. Fredericks pulls a 10 kg box with 30 N of Force a distance of 50 m, at an angle of 50 o with the ground. a. Calculate the work that was done (964 J) b. Calculate the normal force on the suitcase. (75 N) Direction of motion Work: Example 4 A 50-kg crate is pulled 40 m with a force of 100 N at an angle of 37 o. The floor is rough and exerts a frictional force of 50 N. Determine the work done on the crate by each force and the net work done on the crate. (1200 J) F p q = 50 o F fr F N mg q Lab Comments First sentence should be summary/purpose Free body Force was constant in graph A 150,000 kg rocket launches straight up with a thrust of 4.0 X 10 6 N. a. Calculate the work done by thrust at 500 m. (2.0 X 10 9 J) b. Calculate the work done by gravity. (-7.4 X 10 8 J) c. Calculate the net work. (1.26 X 109 J) d. Calculate the speed of the rocket. (130 m/s) 1

2 A 500 g air hockey puck slides across an air table at 2.0 m/s. The player blows on the puck at an angle of 30 o to the horizontal with a force of 1.0 N for 50 cm. The player is trying to slow the puck. a. Calculate the work done by the player. ( J) b. Calculate the final speed of the puck (1.5 m/s) Work: Variable Force Work is really an area: W = Fdx (an integral tells you the area) WORK The magnitude of a force on a spring varies according to F(x) = 1500x 2. Calculate the work done stretching the spring 10 cm from its equilibrium length. A 1500 kg car accelerates from rest. The graph below shows the force on the car. a. Calculate the work done on the car. (1 X 106 J) b. Calculate the speed after 200 m. (37 m/s) (0.50 Joules) A 100 g pinball is launched by pulling back a 20 N/m spring a distance of 20 cm. However, there is friction and m k = a. Calculate the work done by the spring. (0.400 J) b. Calculate the work done by friction. ( J) c. Calculate the speed of the ball on release. (2.8 m/s) Does the Earth Do Work on the Moon? W = Fdcosq W = Fd(cos 90 o ) W = Fd(0) W = 0 v F R 2

3 English Unit of Work Foot-pound English unit of work. Pound Force Foot distance W = Fd = (foot*pound) A 70 kg man on a sled is gliding at 2.0 m/s when he starts down a slippery 10 o slope. He travels for 50 m. a. Calculate the force parallel to the ground pulling him down the hill. (120 N) b. Calculate work done by gravity for the 50 m. (6000 J) c. Calculate his speed at the bottom. Remember that initially he was not at rest. (13 m/s) Conservative and Nonconservative Forces Conservative Forces Work is independent of the path taken Gravity, electromagnetic forces Nonconservative Forces Work depends on the path taken Friction (dissipative forces) Nonconservative Forces Will it take more work to push the box on path A or path B? Or are they the same? B A If nonconservative forces act, use: KE 1 + PE 1 = KE 2 + PE 1 + W fr ½ mv 2 + mgy = ½ mv 2 + mgy + F fr d Mr. Fredericks (100 kg) slides down a 3.5 m tall slide. If he leaves the slide at the bottom at 6.3 m/s, what is the Force of friction and the coefficient of friction for the slide? Assume the slide is 6.0 m long. (0.31) 3.5 m 6.0 m 3

4 A 70 kg skier starts at the top of the slope at 2.0 m/s. The slope is 50 m long and has an elevation of 10 o. There is a wind exerting a 50 N retarding force at the bottom. a. Calculate the work done by gravity (6000 J) b. Calculate the work done by the retarding force. (-2500 J) c. Calculate her speed at the bottom (10 m/s) A 5.0 kg box is attached to one end of a spring (80 N/m). The other end is attached to the wall. The spring is stretched 50 cm by a constant force of 100 N. There is friction and m k = a. Calculate the work done by the pull. (50 J) b. Calculate the work done on the spring. (10 J) c. Calculate the work lost to friction (thermal energy). (7.4 J) d. Calculate the speed of the box at 50 cm (3.6 m/s) [W = 1 / 2 mv / 2 kx 2 + E therm ] Force and Potential Energy F = - du ds Force is the negative of the derivative of the potential energy. Force is the negative slope. Example: Calculate the gravitational force for gravitational Potential energy (mgy) Calculate the force being exerted on a particle given the following potential energy curve: Given the following potential energy graph, sketch the force versus distance graph. 4

5 A gram box is pushed up a 30 o incline with a force of 50.0 N as shown in the figure. The box moves 50.0 cm up the incline. Calculate the work done by the force assuming no friction. Calculate the work done against gravity and the net work done by all the forces on the box. Suppose the box has a mass of 500 grams and m k = Calculate the net work done by all the forces on the box. Power = Work time Power P = W t Metric Unit: Joules/s = Watt. Definition rate at which work is done A powerful engine can do a lot of work quickly. Running and walking up the steps require the same amount of work. Running up steps requires more Power a. A donkey performs 15,000 J of work pulling a wagon for 20 s. What is the donkey s power? b. What power motor is needed to lift a 2000 kg elevator at a constant 3.0 m/s? (Hint: use 1 second in your calculations) c. A motor and cable drags a 300 kg box across a rough floor at 0.50 m/s. The coefficient of kinetic friction is Calculate the necessary power. Horsepower The English Unit of power is horsepower Foot-lb second = Horsepower (hp) 1 hp = 746 Watts 1 hp = ½ Columbus (who sailed in 1492) 1. How much horsepower is required to power a 100 Watt lightbulb? 2. A 1500 kg car has a profile that is 1.6 m wide and 1.4 m high. The coefficient of rolling friction is Calculate the drag force if the car travels at a steady 30 m/s (1/4Av 2 ) (504 N) 2. Calculate the force the car must exert against drag and friction. (798 N) 3. Calculate the power the engine must provide if 25% of the power is lost between the engine and the wheels. Horsepower Consider a 100 hp car engine that can go from 0 to 60 mi/hr in 20 seconds. A 400 hp car could go from zero to 60 mi/hr in 5 seconds. 4 times as powerful means it can do the same work in ¼ the time. 5

6 Horsepower: Example 4 A crane lifts a 200 N box 5 meters in 3 seconds. What is the crane s power in Watts and in horsepower? P = (200)(5)/3 = 333 W 333W/746W = 0.45 hp P = W t Work = Fd P = FDd Dt P = Fv Power and Calculus = F dx dt Power and Calculus: Ex 1 Find the power delivered by a net force at t=2 s to a 0.5 kg mass that moves according to x(t) = 1/3t 3 v = dx/dt v = t 2 v = (2)2 = 4 m/s a = dv/dt a = 2t a = 4 m/s 2 F = ma F = (0.5 kg)(4 m/s 2 ) = 2 N P = Fv = (2N)(4 m/s) Springs and Calculus The force in a spring is variable (F = -kx) Work = 0x F(x) dx Work = 0x -kx dx Work = - ½kx 2 Work = -DPE DPE = ½ kx 2 A particle experiences a force F(x) = 2x. a) Calculate the change in potential energy that the particle undergoes from 0 to 3 m. b) What kind of object might provide the force shown above? c) If the force is now F(x) = 2x 2, calculate the change in potential energy that the particle undergoes from 0 to 3 m. 6

7 Given the following force-distance graph, sketch the potential energy-distance graph. Given the following potential energy-distance graph, sketch the force-distance graph. 8. a) -12 J b) 0 J 10. a) -29 J b) 29 J kj 1.69 kj 1.07 kj J m/s (at 2 m) 4.0 m/s (at 4m) N, 0 N, -50 N 20. b) -12 N (y = 1 m) -48 N (y = 2m) 30. a) 9.8 X 10 5 J b) 1.96 X 10 4 W m 2 34.a) energy b) 1.8 X 10 9 J 36. a, b, c) 50 J (Conservative) 38. a) 400 N b) -2 J c) 22.4 m/s 36. a, b, c) 50 J (Conservative) 38. a) 400 N b) -2 J c) 22.4 m/s 42. a) 230 J b) 230 N c) 6.8 kw 44. a) 15.7 m/s b) 15.7 m/s A horizontal force pulls a 20.0 kg carton across the floor at a constant speed. The coefficient of kinetic friction, m k, is a. Calculate the work done moving the box 3.00 m. b Suppose the force is now at an angle of 30.0 o to the floor as shown in the figure. Calculate the force needed to pull the box across the floor at a constant speed. Be sure to consider any effects the rope may have on the normal force. c. Calculate the work done pulling the box 3.00 m under the conditions in (b). The following problems require calculus. The potential energy of a particle is defined as U = ax 3 bx 2. Determine the formula for the force acting on the particle. The potential energy of a particle is defined as U = U o sinbx. Determine the formula for the force acting on the particle. Calculate the work done from 1.00 m to 3.00 m for a particle that experiences a force F x = 5.0x Starting with the formula for the force of a spring, F spring = -ks, determine the formula for the potential energy stored in a spring. Integrate from 0 to x. 7

8 A 1.50 kg rocket from a craft store generates a thrust of 40.0 N. Using energy-work calculations, determine the speed at 10.0 m. Suppose the rockets only burns for the first 10.0 m. Calculate the total maximum height of the rocket. The following masses are attached to a pulley and cord as shown. Mass M is heavier than mass m. Using energy considerations, find an expression for the speed of either mass just before mass M hits the floor. 8

WORK DONE BY A CONSTANT FORCE

WORK DONE BY A CONSTANT FORCE WORK DONE BY A CONSTANT FORCE The definition of work, W, when a constant force (F) is in the direction of displacement (d) is W = Fd SI unit is the Newton-meter (Nm) = Joule, J If you exert a force of

More information

7. Kinetic Energy and Work

7. Kinetic Energy and Work Kinetic Energy: 7. Kinetic Energy and Work The kinetic energy of a moving object: k = 1 2 mv 2 Kinetic energy is proportional to the square of the velocity. If the velocity of an object doubles, the kinetic

More information

9. The kinetic energy of the moving object is (1) 5 J (3) 15 J (2) 10 J (4) 50 J

9. The kinetic energy of the moving object is (1) 5 J (3) 15 J (2) 10 J (4) 50 J 1. If the kinetic energy of an object is 16 joules when its speed is 4.0 meters per second, then the mass of the objects is (1) 0.5 kg (3) 8.0 kg (2) 2.0 kg (4) 19.6 kg Base your answers to questions 9

More information

Chapter 6 Work and Energy

Chapter 6 Work and Energy Chapter 6 WORK AND ENERGY PREVIEW Work is the scalar product of the force acting on an object and the displacement through which it acts. When work is done on or by a system, the energy of that system

More information

1) 0.33 m/s 2. 2) 2 m/s 2. 3) 6 m/s 2. 4) 18 m/s 2 1) 120 J 2) 40 J 3) 30 J 4) 12 J. 1) unchanged. 2) halved. 3) doubled.

1) 0.33 m/s 2. 2) 2 m/s 2. 3) 6 m/s 2. 4) 18 m/s 2 1) 120 J 2) 40 J 3) 30 J 4) 12 J. 1) unchanged. 2) halved. 3) doubled. Base your answers to questions 1 through 5 on the diagram below which represents a 3.0-kilogram mass being moved at a constant speed by a force of 6.0 Newtons. 4. If the surface were frictionless, the

More information

2.1 Force and Motion Kinematics looks at velocity and acceleration without reference to the cause of the acceleration.

2.1 Force and Motion Kinematics looks at velocity and acceleration without reference to the cause of the acceleration. 2.1 Force and Motion Kinematics looks at velocity and acceleration without reference to the cause of the acceleration. Dynamics looks at the cause of acceleration: an unbalanced force. Isaac Newton was

More information

8. Potential Energy and Conservation of Energy Potential Energy: When an object has potential to have work done on it, it is said to have potential

8. Potential Energy and Conservation of Energy Potential Energy: When an object has potential to have work done on it, it is said to have potential 8. Potential Energy and Conservation of Energy Potential Energy: When an object has potential to have work done on it, it is said to have potential energy, e.g. a ball in your hand has more potential energy

More information

AP Physics - Chapter 8 Practice Test

AP Physics - Chapter 8 Practice Test AP Physics - Chapter 8 Practice Test Multiple Choice Identify the choice that best completes the statement or answers the question. 1. A single conservative force F x = (6.0x 12) N (x is in m) acts on

More information

Ch 8 Potential energy and Conservation of Energy. Question: 2, 3, 8, 9 Problems: 3, 9, 15, 21, 24, 25, 31, 32, 35, 41, 43, 47, 49, 53, 55, 63

Ch 8 Potential energy and Conservation of Energy. Question: 2, 3, 8, 9 Problems: 3, 9, 15, 21, 24, 25, 31, 32, 35, 41, 43, 47, 49, 53, 55, 63 Ch 8 Potential energ and Conservation of Energ Question: 2, 3, 8, 9 Problems: 3, 9, 15, 21, 24, 25, 31, 32, 35, 41, 43, 47, 49, 53, 55, 63 Potential energ Kinetic energ energ due to motion Potential energ

More information

Chapter 7 WORK, ENERGY, AND Power Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable Force Power

Chapter 7 WORK, ENERGY, AND Power Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable Force Power Chapter 7 WORK, ENERGY, AND Power Work Done by a Constant Force Kinetic Energy and the Work-Energy Theorem Work Done by a Variable Force Power Examples of work. (a) The work done by the force F on this

More information

1. Newton s Laws of Motion and their Applications Tutorial 1

1. Newton s Laws of Motion and their Applications Tutorial 1 1. Newton s Laws of Motion and their Applications Tutorial 1 1.1 On a planet far, far away, an astronaut picks up a rock. The rock has a mass of 5.00 kg, and on this particular planet its weight is 40.0

More information

Work, Energy and Power Practice Test 1

Work, Energy and Power Practice Test 1 Name: ate: 1. How much work is required to lift a 2-kilogram mass to a height of 10 meters?. 5 joules. 20 joules. 100 joules. 200 joules 5. ar and car of equal mass travel up a hill. ar moves up the hill

More information

Conservation of Energy Workshop. Academic Resource Center

Conservation of Energy Workshop. Academic Resource Center Conservation of Energy Workshop Academic Resource Center Presentation Outline Understanding Concepts Kinetic Energy Gravitational Potential Energy Elastic Potential Energy Example Conceptual Situations

More information

Work, Energy & Momentum Homework Packet Worksheet 1: This is a lot of work!

Work, Energy & Momentum Homework Packet Worksheet 1: This is a lot of work! Work, Energy & Momentum Homework Packet Worksheet 1: This is a lot of work! 1. A student holds her 1.5-kg psychology textbook out of a second floor classroom window until her arm is tired; then she releases

More information

10.1 Quantitative. Answer: A Var: 50+

10.1 Quantitative. Answer: A Var: 50+ Chapter 10 Energy and Work 10.1 Quantitative 1) A child does 350 J of work while pulling a box from the ground up to his tree house with a rope. The tree house is 4.8 m above the ground. What is the mass

More information

Work, Energy and Power

Work, Energy and Power Work, Energy and Power In this section of the Transport unit, we will look at the energy changes that take place when a force acts upon an object. Energy can t be created or destroyed, it can only be changed

More information

Work, Power, Energy Multiple Choice. PSI Physics. Multiple Choice Questions

Work, Power, Energy Multiple Choice. PSI Physics. Multiple Choice Questions Work, Power, Energy Multiple Choice PSI Physics Name Multiple Choice Questions 1. A block of mass m is pulled over a distance d by an applied force F which is directed in parallel to the displacement.

More information

Ch 7 Kinetic Energy and Work. Question: 7 Problems: 3, 7, 11, 17, 23, 27, 35, 37, 41, 43

Ch 7 Kinetic Energy and Work. Question: 7 Problems: 3, 7, 11, 17, 23, 27, 35, 37, 41, 43 Ch 7 Kinetic Energy and Work Question: 7 Problems: 3, 7, 11, 17, 23, 27, 35, 37, 41, 43 Technical definition of energy a scalar quantity that is associated with that state of one or more objects The state

More information

Physics: Principles and Applications, 6e Giancoli Chapter 4 Dynamics: Newton's Laws of Motion

Physics: Principles and Applications, 6e Giancoli Chapter 4 Dynamics: Newton's Laws of Motion Physics: Principles and Applications, 6e Giancoli Chapter 4 Dynamics: Newton's Laws of Motion Conceptual Questions 1) Which of Newton's laws best explains why motorists should buckle-up? A) the first law

More information

WORKSHEET: KINETIC AND POTENTIAL ENERGY PROBLEMS

WORKSHEET: KINETIC AND POTENTIAL ENERGY PROBLEMS WORKSHEET: KINETIC AND POTENTIAL ENERGY PROBLEMS 1. Stored energy or energy due to position is known as Potential energy. 2. The formula for calculating potential energy is mgh. 3. The three factors that

More information

AP Physics C Fall Final Web Review

AP Physics C Fall Final Web Review Name: Class: _ Date: _ AP Physics C Fall Final Web Review Multiple Choice Identify the choice that best completes the statement or answers the question. 1. On a position versus time graph, the slope of

More information

PHY231 Section 2, Form A March 22, 2012. 1. Which one of the following statements concerning kinetic energy is true?

PHY231 Section 2, Form A March 22, 2012. 1. Which one of the following statements concerning kinetic energy is true? 1. Which one of the following statements concerning kinetic energy is true? A) Kinetic energy can be measured in watts. B) Kinetic energy is always equal to the potential energy. C) Kinetic energy is always

More information

B) 286 m C) 325 m D) 367 m Answer: B

B) 286 m C) 325 m D) 367 m Answer: B Practice Midterm 1 1) When a parachutist jumps from an airplane, he eventually reaches a constant speed, called the terminal velocity. This means that A) the acceleration is equal to g. B) the force of

More information

Chapter 4 Dynamics: Newton s Laws of Motion

Chapter 4 Dynamics: Newton s Laws of Motion Chapter 4 Dynamics: Newton s Laws of Motion Units of Chapter 4 Force Newton s First Law of Motion Mass Newton s Second Law of Motion Newton s Third Law of Motion Weight the Force of Gravity; and the Normal

More information

C B A T 3 T 2 T 1. 1. What is the magnitude of the force T 1? A) 37.5 N B) 75.0 N C) 113 N D) 157 N E) 192 N

C B A T 3 T 2 T 1. 1. What is the magnitude of the force T 1? A) 37.5 N B) 75.0 N C) 113 N D) 157 N E) 192 N Three boxes are connected by massless strings and are resting on a frictionless table. Each box has a mass of 15 kg, and the tension T 1 in the right string is accelerating the boxes to the right at a

More information

Chapter 6. Work and Energy

Chapter 6. Work and Energy Chapter 6 Work and Energy ENERGY IS THE ABILITY TO DO WORK = TO APPLY A FORCE OVER A DISTANCE= Example: push over a distance, pull over a distance. Mechanical energy comes into 2 forms: Kinetic energy

More information

CHAPTER 6 WORK AND ENERGY

CHAPTER 6 WORK AND ENERGY CHAPTER 6 WORK AND ENERGY CONCEPTUAL QUESTIONS. REASONING AND SOLUTION The work done by F in moving the box through a displacement s is W = ( F cos 0 ) s= Fs. The work done by F is W = ( F cos θ). s From

More information

Name Period WORKSHEET: KINETIC AND POTENTIAL ENERGY PROBLEMS. 1. Stored energy or energy due to position is known as energy.

Name Period WORKSHEET: KINETIC AND POTENTIAL ENERGY PROBLEMS. 1. Stored energy or energy due to position is known as energy. Name Period Date WORKSHEET: KINETIC AND POTENTIAL ENERGY PROBLEMS 1. Stored energy or energy due to position is known as energy. 2. The formula for calculating potential energy is. 3. The three factors

More information

Conservative vs. Non-conservative forces Gravitational Potential Energy. Work done by non-conservative forces and changes in mechanical energy

Conservative vs. Non-conservative forces Gravitational Potential Energy. Work done by non-conservative forces and changes in mechanical energy Next topic Conservative vs. Non-conservative forces Gravitational Potential Energy Mechanical Energy Conservation of Mechanical energy Work done by non-conservative forces and changes in mechanical energy

More information

Chapter 5 Using Newton s Laws: Friction, Circular Motion, Drag Forces. Copyright 2009 Pearson Education, Inc.

Chapter 5 Using Newton s Laws: Friction, Circular Motion, Drag Forces. Copyright 2009 Pearson Education, Inc. Chapter 5 Using Newton s Laws: Friction, Circular Motion, Drag Forces Units of Chapter 5 Applications of Newton s Laws Involving Friction Uniform Circular Motion Kinematics Dynamics of Uniform Circular

More information

Work, Kinetic Energy and Potential Energy

Work, Kinetic Energy and Potential Energy Chapter 6 Work, Kinetic Energy and Potential Energy 6.1 The Important Stuff 6.1.1 Kinetic Energy For an object with mass m and speed v, the kinetic energy is defined as K = 1 2 mv2 (6.1) Kinetic energy

More information

PHY231 Section 1, Form B March 22, 2012

PHY231 Section 1, Form B March 22, 2012 1. A car enters a horizontal, curved roadbed of radius 50 m. The coefficient of static friction between the tires and the roadbed is 0.20. What is the maximum speed with which the car can safely negotiate

More information

3 Work, Power and Energy

3 Work, Power and Energy 3 Work, Power and Energy At the end of this section you should be able to: a. describe potential energy as energy due to position and derive potential energy as mgh b. describe kinetic energy as energy

More information

IMPORTANT NOTE ABOUT WEBASSIGN:

IMPORTANT NOTE ABOUT WEBASSIGN: Week 8 homework IMPORTANT NOTE ABOUT WEBASSIGN: In the WebAssign versions of these problems, various details have been changed, so that the answers will come out differently. The method to find the solution

More information

Curso2012-2013 Física Básica Experimental I Cuestiones Tema IV. Trabajo y energía.

Curso2012-2013 Física Básica Experimental I Cuestiones Tema IV. Trabajo y energía. 1. A body of mass m slides a distance d along a horizontal surface. How much work is done by gravity? A) mgd B) zero C) mgd D) One cannot tell from the given information. E) None of these is correct. 2.

More information

physics 111N work & energy

physics 111N work & energy physics 111N work & energy conservation of energy entirely gravitational potential energy kinetic energy turning into gravitational potential energy gravitational potential energy turning into kinetic

More information

Units DEMO spring scales masses

Units DEMO spring scales masses Dynamics the study of the causes and changes of motion Force Force Categories ContactField 4 fundamental Force Types 1 Gravity 2 Weak Nuclear Force 3 Electromagnetic 4 Strong Nuclear Force Units DEMO spring

More information

Work and Energy continued

Work and Energy continued Chapter 6 Work and Energy continued Requested Seat reassignments (Sec. 1) Gram J14 Weber C22 Hardecki B5 Pilallis B18 Murray B19 White B20 Ogden C1 Phan C2 Vites C3 Mccrate C4 Demonstrations Swinging mass,

More information

Name: Partners: Period: Coaster Option: 1. In the space below, make a sketch of your roller coaster.

Name: Partners: Period: Coaster Option: 1. In the space below, make a sketch of your roller coaster. 1. In the space below, make a sketch of your roller coaster. 2. On your sketch, label different areas of acceleration. Put a next to an area of negative acceleration, a + next to an area of positive acceleration,

More information

LAB 6: GRAVITATIONAL AND PASSIVE FORCES

LAB 6: GRAVITATIONAL AND PASSIVE FORCES 55 Name Date Partners LAB 6: GRAVITATIONAL AND PASSIVE FORCES And thus Nature will be very conformable to herself and very simple, performing all the great Motions of the heavenly Bodies by the attraction

More information

LAB 6 - GRAVITATIONAL AND PASSIVE FORCES

LAB 6 - GRAVITATIONAL AND PASSIVE FORCES L06-1 Name Date Partners LAB 6 - GRAVITATIONAL AND PASSIVE FORCES OBJECTIVES And thus Nature will be very conformable to herself and very simple, performing all the great Motions of the heavenly Bodies

More information

= Ps cos 0 = (150 N)(7.0 m) = J F N. s cos 180 = µ k

= Ps cos 0 = (150 N)(7.0 m) = J F N. s cos 180 = µ k Week 5 homework IMPORTANT NOTE ABOUT WEBASSIGN: In the WebAssign versions o these problems, various details have been changed, so that the answers will come out dierently. The method to ind the solution

More information

KE =? v o. Page 1 of 12

KE =? v o. Page 1 of 12 Page 1 of 12 CTEnergy-1. A mass m is at the end of light (massless) rod of length R, the other end of which has a frictionless pivot so the rod can swing in a vertical plane. The rod is initially horizontal

More information

Chapter 4. Forces and Newton s Laws of Motion. continued

Chapter 4. Forces and Newton s Laws of Motion. continued Chapter 4 Forces and Newton s Laws of Motion continued 4.9 Static and Kinetic Frictional Forces When an object is in contact with a surface forces can act on the objects. The component of this force acting

More information

Physics 2A, Sec B00: Mechanics -- Winter 2011 Instructor: B. Grinstein Final Exam

Physics 2A, Sec B00: Mechanics -- Winter 2011 Instructor: B. Grinstein Final Exam Physics 2A, Sec B00: Mechanics -- Winter 2011 Instructor: B. Grinstein Final Exam INSTRUCTIONS: Use a pencil #2 to fill your scantron. Write your code number and bubble it in under "EXAM NUMBER;" an entry

More information

At the skate park on the ramp

At the skate park on the ramp At the skate park on the ramp 1 On the ramp When a cart rolls down a ramp, it begins at rest, but starts moving downward upon release covers more distance each second When a cart rolls up a ramp, it rises

More information

Work-Energy Bar Charts

Work-Energy Bar Charts Name: Work-Energy Bar Charts Read from Lesson 2 of the Work, Energy and Power chapter at The Physics Classroom: http://www.physicsclassroom.com/class/energy/u5l2c.html MOP Connection: Work and Energy:

More information

www.mathsbox.org.uk Displacement (x) Velocity (v) Acceleration (a) x = f(t) differentiate v = dx Acceleration Velocity (v) Displacement x

www.mathsbox.org.uk Displacement (x) Velocity (v) Acceleration (a) x = f(t) differentiate v = dx Acceleration Velocity (v) Displacement x Mechanics 2 : Revision Notes 1. Kinematics and variable acceleration Displacement (x) Velocity (v) Acceleration (a) x = f(t) differentiate v = dx differentiate a = dv = d2 x dt dt dt 2 Acceleration Velocity

More information

Work Energy & Power. September 2000 Number 05. 1. Work If a force acts on a body and causes it to move, then the force is doing work.

Work Energy & Power. September 2000 Number 05. 1. Work If a force acts on a body and causes it to move, then the force is doing work. PhysicsFactsheet September 2000 Number 05 Work Energy & Power 1. Work If a force acts on a body and causes it to move, then the force is doing work. W = Fs W = work done (J) F = force applied (N) s = distance

More information

v v ax v a x a v a v = = = Since F = ma, it follows that a = F/m. The mass of the arrow is unchanged, and ( )

v v ax v a x a v a v = = = Since F = ma, it follows that a = F/m. The mass of the arrow is unchanged, and ( ) Week 3 homework IMPORTANT NOTE ABOUT WEBASSIGN: In the WebAssign versions of these problems, various details have been changed, so that the answers will come out differently. The method to find the solution

More information

Physics 125 Practice Exam #3 Chapters 6-7 Professor Siegel

Physics 125 Practice Exam #3 Chapters 6-7 Professor Siegel Physics 125 Practice Exam #3 Chapters 6-7 Professor Siegel Name: Lab Day: 1. A concrete block is pulled 7.0 m across a frictionless surface by means of a rope. The tension in the rope is 40 N; and the

More information

Chapter 8: Potential Energy and Conservation of Energy. Work and kinetic energy are energies of motion.

Chapter 8: Potential Energy and Conservation of Energy. Work and kinetic energy are energies of motion. Chapter 8: Potential Energy and Conservation of Energy Work and kinetic energy are energies of motion. Consider a vertical spring oscillating with mass m attached to one end. At the extreme ends of travel

More information

Chapter 5 Newton s Laws of Motion

Chapter 5 Newton s Laws of Motion Chapter 5 Newton s Laws of Motion Sir Isaac Newton (1642 1727) Developed a picture of the universe as a subtle, elaborate clockwork slowly unwinding according to well-defined rules. The book Philosophiae

More information

EDUH 1017 - SPORTS MECHANICS

EDUH 1017 - SPORTS MECHANICS 4277(a) Semester 2, 2011 Page 1 of 9 THE UNIVERSITY OF SYDNEY EDUH 1017 - SPORTS MECHANICS NOVEMBER 2011 Time allowed: TWO Hours Total marks: 90 MARKS INSTRUCTIONS All questions are to be answered. Use

More information

Physics 11 Assignment KEY Dynamics Chapters 4 & 5

Physics 11 Assignment KEY Dynamics Chapters 4 & 5 Physics Assignment KEY Dynamics Chapters 4 & 5 ote: for all dynamics problem-solving questions, draw appropriate free body diagrams and use the aforementioned problem-solving method.. Define the following

More information

Conceptual Questions: Forces and Newton s Laws

Conceptual Questions: Forces and Newton s Laws Conceptual Questions: Forces and Newton s Laws 1. An object can have motion only if a net force acts on it. his statement is a. true b. false 2. And the reason for this (refer to previous question) is

More information

Physics Notes Class 11 CHAPTER 5 LAWS OF MOTION

Physics Notes Class 11 CHAPTER 5 LAWS OF MOTION 1 P a g e Inertia Physics Notes Class 11 CHAPTER 5 LAWS OF MOTION The property of an object by virtue of which it cannot change its state of rest or of uniform motion along a straight line its own, is

More information

ENERGYand WORK (PART I and II) 9-MAC

ENERGYand WORK (PART I and II) 9-MAC ENERGYand WORK (PART I and II) 9-MAC Purpose: To understand work, potential energy, & kinetic energy. To understand conservation of energy and how energy is converted from one form to the other. Apparatus:

More information

Chapter 4. Forces and Newton s Laws of Motion. continued

Chapter 4. Forces and Newton s Laws of Motion. continued Chapter 4 Forces and Newton s Laws of Motion continued Clicker Question 4.3 A mass at rest on a ramp. How does the friction between the mass and the table know how much force will EXACTLY balance the gravity

More information

Physics 201 Homework 8

Physics 201 Homework 8 Physics 201 Homework 8 Feb 27, 2013 1. A ceiling fan is turned on and a net torque of 1.8 N-m is applied to the blades. 8.2 rad/s 2 The blades have a total moment of inertia of 0.22 kg-m 2. What is the

More information

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) Vector A has length 4 units and directed to the north. Vector B has length 9 units and is directed

More information

Gravitational Potential Energy

Gravitational Potential Energy Gravitational Potential Energy Consider a ball falling from a height of y 0 =h to the floor at height y=0. A net force of gravity has been acting on the ball as it drops. So the total work done on the

More information

Serway_ISM_V1 1 Chapter 4

Serway_ISM_V1 1 Chapter 4 Serway_ISM_V1 1 Chapter 4 ANSWERS TO MULTIPLE CHOICE QUESTIONS 1. Newton s second law gives the net force acting on the crate as This gives the kinetic friction force as, so choice (a) is correct. 2. As

More information

KE = ½mv 2 PE = mgh W = Fdcosθ THINK ENERGY! (KE F + PE F ) = (KE 0 + PE 0 ) + W NC. Tues Oct 6 Assign 7 Fri Pre-class Thursday

KE = ½mv 2 PE = mgh W = Fdcosθ THINK ENERGY! (KE F + PE F ) = (KE 0 + PE 0 ) + W NC. Tues Oct 6 Assign 7 Fri Pre-class Thursday Tues Oct 6 Assign 7 Fri Pre-class Thursday Conservation of Energy Work, KE, PE, Mech Energy Power To conserve total energy means that the total energy is constant or stays the same. With Work, we now have

More information

Friction and Newton s 3rd law

Friction and Newton s 3rd law Lecture 4 Friction and Newton s 3rd law Pre-reading: KJF 4.8 Frictional Forces Friction is a force exerted by a surface. The frictional force is always parallel to the surface Due to roughness of both

More information

SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.

SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. Exam Name SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 1) A person on a sled coasts down a hill and then goes over a slight rise with speed 2.7 m/s.

More information

Section 6.4: Work. We illustrate with an example.

Section 6.4: Work. We illustrate with an example. Section 6.4: Work 1. Work Performed by a Constant Force Riemann sums are useful in many aspects of mathematics and the physical sciences than just geometry. To illustrate one of its major uses in physics,

More information

Forces: Equilibrium Examples

Forces: Equilibrium Examples Physics 101: Lecture 02 Forces: Equilibrium Examples oday s lecture will cover extbook Sections 2.1-2.7 Phys 101 URL: http://courses.physics.illinois.edu/phys101/ Read the course web page! Physics 101:

More information

Chapter 4: Newton s Laws: Explaining Motion

Chapter 4: Newton s Laws: Explaining Motion Chapter 4: Newton s Laws: Explaining Motion 1. All except one of the following require the application of a net force. Which one is the exception? A. to change an object from a state of rest to a state

More information

TEACHER ANSWER KEY November 12, 2003. Phys - Vectors 11-13-2003

TEACHER ANSWER KEY November 12, 2003. Phys - Vectors 11-13-2003 Phys - Vectors 11-13-2003 TEACHER ANSWER KEY November 12, 2003 5 1. A 1.5-kilogram lab cart is accelerated uniformly from rest to a speed of 2.0 meters per second in 0.50 second. What is the magnitude

More information

UNIT 2D. Laws of Motion

UNIT 2D. Laws of Motion Name: Regents Physics Date: Mr. Morgante UNIT 2D Laws of Motion Laws of Motion Science of Describing Motion is Kinematics. Dynamics- the study of forces that act on bodies in motion. First Law of Motion

More information

PHYS 211 FINAL FALL 2004 Form A

PHYS 211 FINAL FALL 2004 Form A 1. Two boys with masses of 40 kg and 60 kg are holding onto either end of a 10 m long massless pole which is initially at rest and floating in still water. They pull themselves along the pole toward each

More information

AP Physics C. Oscillations/SHM Review Packet

AP Physics C. Oscillations/SHM Review Packet AP Physics C Oscillations/SHM Review Packet 1. A 0.5 kg mass on a spring has a displacement as a function of time given by the equation x(t) = 0.8Cos(πt). Find the following: a. The time for one complete

More information

When showing forces on diagrams, it is important to show the directions in which they act as well as their magnitudes.

When showing forces on diagrams, it is important to show the directions in which they act as well as their magnitudes. When showing forces on diagrams, it is important to show the directions in which they act as well as their magnitudes. mass M, the force of attraction exerted by the Earth on an object, acts downwards.

More information

F13--HPhys--Q5 Practice

F13--HPhys--Q5 Practice Name: Class: Date: ID: A F13--HPhys--Q5 Practice Multiple Choice Identify the choice that best completes the statement or answers the question. 1. A vector is a quantity that has a. time and direction.

More information

Weight The weight of an object is defined as the gravitational force acting on the object. Unit: Newton (N)

Weight The weight of an object is defined as the gravitational force acting on the object. Unit: Newton (N) Gravitational Field A gravitational field as a region in which an object experiences a force due to gravitational attraction Gravitational Field Strength The gravitational field strength at a point in

More information

General Physical Science

General Physical Science General Physical Science Chapter 4 Work and Energy Work The work done by a constant force F acting upon an object is the product of the magnitude of the force (or component of the force) and the parallel

More information

VELOCITY, ACCELERATION, FORCE

VELOCITY, ACCELERATION, FORCE VELOCITY, ACCELERATION, FORCE velocity Velocity v is a vector, with units of meters per second ( m s ). Velocity indicates the rate of change of the object s position ( r ); i.e., velocity tells you how

More information

1) The gure below shows the position of a particle (moving along a straight line) as a function of time. Which of the following statements is true?

1) The gure below shows the position of a particle (moving along a straight line) as a function of time. Which of the following statements is true? Physics 2A, Sec C00: Mechanics -- Winter 2011 Instructor: B. Grinstein Final Exam INSTRUCTIONS: Use a pencil #2 to ll your scantron. Write your code number and bubble it in under "EXAM NUMBER;" an entry

More information

Exam 2 is at 7 pm tomorrow Conflict is at 5:15 pm in 151 Loomis

Exam 2 is at 7 pm tomorrow Conflict is at 5:15 pm in 151 Loomis * By request, but I m not vouching for these since I didn t write them Exam 2 is at 7 pm tomorrow Conflict is at 5:15 pm in 151 Loomis There are extra office hours today & tomorrow Lots of practice exams

More information

Work and Energy. W =!KE = KE f

Work and Energy. W =!KE = KE f Activity 19 PS-2826 Work and Energy Mechanics: work-energy theorem, conservation of energy GLX setup file: work energy Qty Equipment and Materials Part Number 1 PASPORT Xplorer GLX PS-2002 1 PASPORT Motion

More information

FORCES AND MOTION UNIT TEST. Multiple Choice: Draw a Circle Completely around the ONE BEST answer.

FORCES AND MOTION UNIT TEST. Multiple Choice: Draw a Circle Completely around the ONE BEST answer. FORCES AND MOTION UNIT TEST Multiple Choice: Draw a Circle Completely around the ONE BEST answer. 1. A force acting on an object does no work if a. a machine is used to move the object. b. the force is

More information

6 WORK and ENERGY. 6.0 Introduction. 6.1 Work and kinetic energy. Objectives

6 WORK and ENERGY. 6.0 Introduction. 6.1 Work and kinetic energy. Objectives 6 WORK and ENERGY Chapter 6 Work and Energy Objectives After studying this chapter you should be able to calculate work done by a force; be able to calculate kinetic energy; be able to calculate power;

More information

F N A) 330 N 0.31 B) 310 N 0.33 C) 250 N 0.27 D) 290 N 0.30 E) 370 N 0.26

F N A) 330 N 0.31 B) 310 N 0.33 C) 250 N 0.27 D) 290 N 0.30 E) 370 N 0.26 Physics 23 Exam 2 Spring 2010 Dr. Alward Page 1 1. A 250-N force is directed horizontally as shown to push a 29-kg box up an inclined plane at a constant speed. Determine the magnitude of the normal force,

More information

STAAR Science Tutorial 25 TEK 8.6C: Newton s Laws

STAAR Science Tutorial 25 TEK 8.6C: Newton s Laws Name: Teacher: Pd. Date: STAAR Science Tutorial 25 TEK 8.6C: Newton s Laws TEK 8.6C: Investigate and describe applications of Newton's law of inertia, law of force and acceleration, and law of action-reaction

More information

Scalar versus Vector Quantities. Speed. Speed: Example Two. Scalar Quantities. Average Speed = distance (in meters) time (in seconds) v =

Scalar versus Vector Quantities. Speed. Speed: Example Two. Scalar Quantities. Average Speed = distance (in meters) time (in seconds) v = Scalar versus Vector Quantities Scalar Quantities Magnitude (size) 55 mph Speed Average Speed = distance (in meters) time (in seconds) Vector Quantities Magnitude (size) Direction 55 mph, North v = Dx

More information

Midterm Solutions. mvr = ω f (I wheel + I bullet ) = ω f 2 MR2 + mr 2 ) ω f = v R. 1 + M 2m

Midterm Solutions. mvr = ω f (I wheel + I bullet ) = ω f 2 MR2 + mr 2 ) ω f = v R. 1 + M 2m Midterm Solutions I) A bullet of mass m moving at horizontal velocity v strikes and sticks to the rim of a wheel a solid disc) of mass M, radius R, anchored at its center but free to rotate i) Which of

More information

Exam 2 Review Questions PHY Exam 2

Exam 2 Review Questions PHY Exam 2 Exam 2 Review Questions PHY 2425 - Exam 2 Section: 4 1 Topic: Newton's First Law: The Law of Inertia Type: Conceptual 1 According to Newton's law of inertia, A) objects moving with an initial speed relative

More information

1. Mass, Force and Gravity

1. Mass, Force and Gravity STE Physics Intro Name 1. Mass, Force and Gravity Before attempting to understand force, we need to look at mass and acceleration. a) What does mass measure? The quantity of matter(atoms) b) What is the

More information

Problem Set 1. Ans: a = 1.74 m/s 2, t = 4.80 s

Problem Set 1. Ans: a = 1.74 m/s 2, t = 4.80 s Problem Set 1 1.1 A bicyclist starts from rest and after traveling along a straight path a distance of 20 m reaches a speed of 30 km/h. Determine her constant acceleration. How long does it take her to

More information

This week s homework. 2 parts Quiz on Friday, Ch. 4 Today s class: Newton s third law Friction Pulleys tension. PHYS 2: Chap.

This week s homework. 2 parts Quiz on Friday, Ch. 4 Today s class: Newton s third law Friction Pulleys tension. PHYS 2: Chap. This week s homework. 2 parts Quiz on Friday, Ch. 4 Today s class: Newton s third law Friction Pulleys tension PHYS 2: Chap. 19, Pg 2 1 New Topic Phys 1021 Ch 7, p 3 A 2.0 kg wood box slides down a vertical

More information

Chapter 7: Momentum and Impulse

Chapter 7: Momentum and Impulse Chapter 7: Momentum and Impulse 1. When a baseball bat hits the ball, the impulse delivered to the ball is increased by A. follow through on the swing. B. rapidly stopping the bat after impact. C. letting

More information

questions: force and motion I

questions: force and motion I questions: force and motion I problem 1 The figure below is an overhead view of a 12 kg tire that is to be pulled by three ropes. One force (F l, with magnitude 50 N) is indicated. Orient the other two

More information

Physics I Honors: Chapter 4 Practice Exam

Physics I Honors: Chapter 4 Practice Exam Physics I Honors: Chapter 4 Practice Exam Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. 1. Which of the following statements does not describe

More information

W i f(x i ) x. i=1. f(x i ) x = i=1

W i f(x i ) x. i=1. f(x i ) x = i=1 Work Force If an object is moving in a straight line with position function s(t), then the force F on the object at time t is the product of the mass of the object times its acceleration. F = m d2 s dt

More information

Objective: Work Done by a Variable Force Work Done by a Spring. Homework: Assignment (1-25) Do PROBS # (64, 65) Ch. 6, + Do AP 1986 # 2 (handout)

Objective: Work Done by a Variable Force Work Done by a Spring. Homework: Assignment (1-25) Do PROBS # (64, 65) Ch. 6, + Do AP 1986 # 2 (handout) Double Date: Objective: Work Done by a Variable Force Work Done by a Spring Homework: Assignment (1-25) Do PROBS # (64, 65) Ch. 6, + Do AP 1986 # 2 (handout) AP Physics B Mr. Mirro Work Done by a Variable

More information

Energy - Key Vocabulary

Energy - Key Vocabulary Energy - Key Vocabulary Term Potential Energy Kinetic Energy Joules Gravity Definition The energy an object possesses due to its position. PE = mgh The energy an object possesses when it is in motion.

More information

Review Chapters 2, 3, 4, 5

Review Chapters 2, 3, 4, 5 Review Chapters 2, 3, 4, 5 4) The gain in speed each second for a freely-falling object is about A) 0. B) 5 m/s. C) 10 m/s. D) 20 m/s. E) depends on the initial speed 9) Whirl a rock at the end of a string

More information

Work. Work = Force x parallel distance (parallel component of displacement) F v

Work. Work = Force x parallel distance (parallel component of displacement) F v Work Work = orce x parallel distance (parallel component of displacement) W k = d parallel d parallel Units: N m= J = " joules" = ( kg m2/ s2) = average force computed over the distance r r When is not

More information