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

Save this PDF as:

Size: px
Start display at page:

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

## Transcription

1 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 is the same, but you will need to repeat part o the calculation to ind out what your answer should have been. WebAssign Problem 1: During a tug-o-war, team A pulls on team B by applying a orce o 1100 N to the rope between them. How much work does team A do i they pull team B toward them a distance o 2.0 m? REASONING AND SOLUTION We will assume that the tug-o-war rope remains parallel to the ground, so that the orce that moves team B is in the same direction as the displacement. According to Equation 6.1, the work done by team A is W = (F cos )s = (1100 N)(cos 0 )(2.0 m) = J WebAssign Problem 2: A 55-kg box is being pushed a distance o 7.0 m across the loor by a orce whose magnitude is 150 N. The orce is parallel to the displacement o the box. The coeicient o kinetic riction is Determine the work done on the box by each o the our orces that act on the box. Be sure to include the proper plus or minus sign or the work done by each orce. REASONING AND SOLUTION The applied orce does work W P = Ps cos 0 = (150 N)(7.0 m) = J The rictional orce does work W = k s cos 180 = µ k F N s where F N = mg, so W = (0.25)(55 kg)(9.80 m/s 2 )(7.0 m) = 940 J, since they both act at a 90 angle to the displacement. WebAssign Problem 3: The concepts in this problem are similar to those in Multiple- Concept Example 4, except that the orce doing the work in this problem is the tension in the cable. A rescue helicopter lits a 79-kg person straight up by means o a cable. The person has an upward acceleration o 0.70 m/s 2 and is lited rom rest through a distance o 11 m. (a) What is the tension in the cable? How much work is done by (b) the tension

2 in the cable and (c) the person s weight? (d) Use the work energy theorem and ind the inal speed o the person. REASONING Since the person has an upward acceleration, there must be a net orce acting in the upward direction. The net orce ΣF y is related to the acceleration a y by Newton s second law, Σ Fy = may, where m is the mass o the person. This relation will allow us to determine the tension in the cable. The work done by the tension and the person s weight can be ound directly rom the deinition o work, Equation 6.1. SOLUTION a. The ree-body diagram at the right shows the two orces that act on the person. Applying Newton s second law, we have T s +y T mg = ma Σ F y y Solving or the magnitude o the tension in the cable yields mg T = m(a y + g) = (79 kg)(0.70 m/s m/s 2 ) = N b. The work done by the tension in the cable is 2 3 ( ) WT = T cos s = ( N) (cos 0 ) (11 m) = J (6.1) c. The work done by the person s weight is ( ) ( ) W = mg s = (6.1) 2 3 W cos (79 kg) 9.8 m/s (cos 180 ) (11 m) = J d. The work-energy theorem relates the work done by the two orces to the change in the kinetic energy o the person. The work done by the two orces is W = W T + W W : W T + WW = mv 2 mv (6.3) W Solving this equation or the inal speed o the person gives

3 2 v = v + W + W m ( ) 2 0 T W = ( 0 m/s ) + ( J J ) = 4 m / s 79 kg WebAssign Problem 4: A 0.60-kg basketball is dropped out o a window that is 6.1 m above the ground. The ball is caught by a person whose hands are 1.5 m above the ground. (a) How much work is done on the ball by its weight? What is the gravitational potential energy o the basketball, relative to the ground, when it is (b) released and (c) caught? (d) How is the change (PE PE 0 ) in the ball s gravitational potential energy related to the work done by its weight? REASONING The work done by the weight o the basketball is given by Equation 6.1 as W = ( F cos ) s, where F = mg is the magnitude o the weight, is the angle between the weight and the displacement, and s is the magnitude o the displacement. The drawing shows that the weight and displacement are parallel, so that = 0. The potential energy o the basketball is given by Equation 6.5 as PE = mgh, where h is the height o the ball above the ground. SOLUTION a. The work done by the weight o the basketball is ( cos ) W = F s = mg (cos 0 )(h 0 h ) = (0.60 kg)(9.80 m/s 2 )(6.1 m 1.5 m) = 27 J is b. The potential energy o the ball, relative to the ground, when it is released PE 0 = mgh 0 = (0.60 kg)(9.80 m/s 2 )(6.1 m) = 36 J (6.5) c. The potential energy o the ball, relative to the ground, when it is caught is PE = mgh = (0.60 kg)(9.80 m/s 2 )(1.5 m) = 8.8 J (6.5) d. The change in the ball s gravitational potential energy is PE = PE PE 0 = 8.8 J 36 J = 27 J We see that the change in the gravitational potential energy is equal to 27 J = W, where W is the work done by the weight o the ball (see part a).

4 WebAssign Problem 5: A person starts rom rest at the top o a large rictionless spherical surace, and slides into the water below (see the drawing). At what angle does the person leave the surace? (Hint: When the person leaves the surace, the normal orce is zero.) REASONING AND SOLUTION I air resistance is ignored, the only nonconservative orce that acts on the person is the normal orce exerted on the person by the surace. Since this orce is always perpendicular to the direction o the displacement, the work done by the normal orce is zero. We can conclude, thereore, that mechanical energy is conserved. (1) 1 2 mv mgh 0 = 1 2 mv 2 + mgh where the inal state pertains to the position where the person leaves the surace. Since the person starts rom rest v 0 = 0 m/s. Since the radius o the surace is r, h 0 = r, and h = r cos where is the angle at which the person leaves the surace. Equation (1) becomes r r r cos mgr = 1 2 mv 2 + mg(r cos ) (2) In general, as the person slides down the surace, the two orces that act on him are the normal orce F N and the weight mg. The centripetal orce required to keep the person moving in the circular path is the resultant o F N and the radial component o the weight, mg cos. When the person leaves the surace, the normal orce is zero, and the radial component o the weight provides the centripetal orce. mg cos mg F N mg cos = mv 2 r v 2 = gr cos (3)

5 Substituting this expression or v 2 into Equation (2) gives Solving or gives 1 2 mgr = mg( r cos ) + mg( r cos ) 1 2 = cos = 48 3 WebAssign Problem 6: Bicyclists in the Tour de France do enormous amounts o work during a race. For example, the average power per kilogram generated by Lance Armstrong (m = 75.0) is 6.50 W per kilogram o his body mass. (a) How much work does he do during a 135-km race in which his average speed is 12.0 m/s? (b) Oten, the work done is expressed in nutritional Calories rather than in joules. Express the work done in part (a) in terms o nutritional Calories, noting that nutritional Calories. REASONING The work W done is equal to the average power P multiplied by the time t, or W = Pt (6.10a) The average power is the average power generated per kilogram o body mass multiplied by Armstrong s mass. The time o the race is the distance s traveled divided by the average speed v, or t = s / v (see Equation 2.1). SOLUTION a. Substituting t = s / v into Equation 6.10a gives s W = Pt = P = v ( ) W kg kg P m 12.0 m/s 6 = J b. Since 1 joule = nutritional calories, the work done is ( ) 6 6 W = joules = joules nutritional calories 1 joule 3 = nutritional calories

6 WebAssign Problem 7: Suppose in Figure 6.2 that o work are done by the orce ( ) in moving the suitcase a distance o 50.0 m. At what angle is the orce oriented with respect to the ground? REASONING AND SOLUTION Solving Equation 6.1 or the angle, we obtain 3 1 W J = cos = cos = 42.8 F s (30.0 N)(50.0 m) WebAssign Problem 8: The drawing shows a version o the loop-the-loop trick or a small car. I the car is given an initial speed o 4.0 m/s, what is the largest value that the radius r can have i the car is to remain in contact with the circular track at all times? REASONING AND SOLUTION When the car is at the top o the track the centripetal orce consists o the ull weight o the car. mv 2 /r = mg gives Applying the conservation o energy between the bottom and the top o the track (1/2)mv mg(2r) = (1/2)mv 0 Using both o the above equations 2 v 0 = 5gr so

7 r = v 0 2 /(5g) = (4.00 m/s) 2 /(49.0 m/s 2 ) = m Practice conceptual problems: 5. A ball has a speed o 15 m/s. Only one external orce acts on the ball. Ater this orce acts, the speed o the ball is 7 m/s. Has the orce done positive or negative work? Explain. REASONING AND SOLUTION The speed o the ball decreases; thereore, the ball is subjected to an external resistive orce. A resistive orce always points opposite to the direction o the displacement o the ball. Thereore, the external orce does negative work. Using the work-energy theorem, we see that the change in the kinetic energy o the ball is negative; thereore, the total work done on the ball is negative. We can conclude, thereore, that the net orce did negative work on the ball. 8. The speed o a particle doubles and then doubles again because a net external orce acts on it. Does the net orce do more work during the irst or the second doubling? Justiy your answer. REASONING AND SOLUTION The speed o a particle doubles and then doubles again, because a net external orce acts on it. Let m and v 0 represent the mass and initial speed o the particle, respectively. During the irst doubling, the change in the kinetic energy o the particle is ( ) = m v mv = mv KE KE 2 During the second doubling, the change in the kinetic energy o the particle is ( ) ( ) = m v m v = mv0 KE KE From the work-energy theorem, we know that a change in kinetic energy is equal to the work done by the net external orce. Thereore, more work is done by the net orce during the second doubling. 14. A person is riding on a Ferris wheel. When the wheel makes one complete turn, is the net work done by the gravitational orce positive, negative, or zero? Justiy your answer. REASONING AND SOLUTION As the person moves downward rom the top o the Ferris wheel, his displacement points downward. Since the person s weight also points downward, the work done by gravity is positive. As the person moves upward rom the bottom, his displacement points upward. Since the weight still points

8 downward, the work done by gravity is negative. The magnitude o the work done in each hal cycle is the same; thereore, the net work done in one revolution is zero. 17. The drawing shows an empty uel tank about to be released by three dierent jet planes. At the moment o release, each plane has the same speed and each tank is at the same height above the ground. However, the directions o travel are dierent. In the absence o air resistance, do the tanks have dierent speeds when they hit the ground? I so, which tank has the largest speed and which has the smallest speed? Explain. REASONING AND SOLUTION Since each plane has the same speed, the kinetic energy o each uel tank will be the same at the instant o release. Since each plane is at the same height above the ground, each uel tank must all through the same vertical displacement. Thereore, the work done by gravity on each uel tank is the same. From the work-energy theorem, each uel tank will gain the same amount o kinetic energy during the all. Thereore, each uel tank will hit the ground with the same speed.

### 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

### CHAPTER 3 FORCES & NEWTON S LAW OF MOTION

CHAPTER 3 FORCES & NEWTON S LAW OF MOTION 3. The concepts o orce and mass FORCE A orce is a push or pull upon an object resulting rom the object's interaction with another object. Force is a quantity which

### Work, Energy & Power. AP Physics B

ork, Energy & Power AP Physics B There are many dierent TYPES o Energy. Energy is expressed in JOULES (J) 4.19 J = 1 calorie Energy can be expressed more speciically by using the term ORK() ork = The Scalar

### F) The work by F 6 is zero. The force is perpendicular to the dispalcement.

Phys 00A Homework 6 Chapter 7 All Work and No Play A) The work by is zero. The orce is perpedicular to the dispalcement. B) The work by is positive. The projection o the orce on the direction o the dispalcement

### Problem Set 5 Work and Kinetic Energy Solutions

MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department o Physics Physics 8.1 Fall 1 Problem Set 5 Work and Kinetic Energy Solutions Problem 1: Work Done by Forces a) Two people push in opposite directions on

### Physics 201 Homework 5

Physics 201 Homework 5 Feb 6, 2013 1. The (non-conservative) force propelling a 1500-kilogram car up a mountain -1.21 10 6 joules road does 4.70 10 6 joules of work on the car. The car starts from rest

### Chapter 10: Energy and Work. Slide 10-2

Chapter 10: Energy and Work Slide 10-2 Forms of Energy Mechanical Energy K U g U s Thermal Energy Other forms include E th E chem E nuclear The Basic Energy Model An exchange of energy between the system

### Homework: 1, 2, 8, 15, 24, 26, 29, 36, 43 (p )

Homework:,, 8, 5, 4, 6, 9, 36, 43 (p. 59-63) . A proton (mass m=.67 x 0-7 kg) is being accelerated along a straight line at 3.6 x 0 5 m/s in a machine. I the proton has an initial speed o.4 x 0 7 m/s and

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

### Solving Newton s Second Law Problems

Solving ewton s Second Law Problems Michael Fowler, Phys 142E Lec 8 Feb 5, 2009 Zero Acceleration Problems: Forces Add to Zero he Law is F ma : the acceleration o a given body is given by the net orce

### 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

### 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

### Chapter 6. Work and Energy

Chapter 6 Work and Energy The concept of forces acting on a mass (one object) is intimately related to the concept of ENERGY production or storage. A mass accelerated to a non-zero speed carries 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

### AP1 WEP. Answer: E. The final velocities of the balls are given by v = 2gh.

1. Bowling Ball A is dropped from a point halfway up a cliff. A second identical bowling ball, B, is dropped simultaneously from the top of the cliff. Comparing the bowling balls at the instant they reach

### 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

### Work. Work = Force distance (the force must be parallel to movement) OR Work = (Force)(cos θ)(distance)

Work Work = Force distance (the force must be parallel to movement) OR Work = (Force)(cos θ)(distance) When you are determining the force parallel to the movement you can do this manually and keep track

### Physics 2101, First Exam, Fall 2007

Physics 2101, First Exam, Fall 2007 September 4, 2007 Please turn OFF your cell phone and MP3 player! Write down your name and section number in the scantron form. Make sure to mark your answers in the

### Solutions to Homework Set #10 Phys2414 Fall 2005

Solution Set #0 Solutions to Homework Set #0 Phys244 Fall 2005 Note: The numbers in the boxes correspond to those that are generated by WebAssign. The numbers on your individual assignment will vary. Any

### 3600 s 1 h. 24 h 1 day. 1 day

Week 7 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

### 2. (P2.1 A) a) A car travels 150 km in 3 hours, what is the cars average speed?

Physics: Review for Final Exam 1 st Semester Name Hour P2.1A Calculate the average speed of an object using the change of position and elapsed time 1. (P2.1 A) What is your average speed if you run 140

### Exercises on Work, Energy, and Momentum. A B = 20(10)cos98 A B 28

Exercises on Work, Energy, and Momentum Exercise 1.1 Consider the following two vectors: A : magnitude 20, direction 37 North of East B : magnitude 10, direction 45 North of West Find the scalar product

### 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,

### Concept Review. Physics 1

Concept Review Physics 1 Speed and Velocity Speed is a measure of how much distance is covered divided by the time it takes. Sometimes it is referred to as the rate of motion. Common units for speed or

### 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

### 2.2 NEWTON S LAWS OF MOTION

2.2 NEWTON S LAWS OF MOTION Sir Isaac Newton (1642-1727) made a systematic study of motion and extended the ideas of Galileo (1564-1642). He summed up Galileo s observation in his three laws of motion

### 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,

### 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

### Work and Conservation of Energy

Work and Conservation of Energy Topics Covered: 1. The definition of work in physics. 2. The concept of potential energy 3. The concept of kinetic energy 4. Conservation of Energy General Remarks: Two

### 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

### Ground Rules. PC1221 Fundamentals of Physics I. Force. Zero Net Force. Lectures 9 and 10 The Laws of Motion. Dr Tay Seng Chuan

PC1221 Fundamentals of Physics I Lectures 9 and 10 he Laws of Motion Dr ay Seng Chuan 1 Ground Rules Switch off your handphone and pager Switch off your laptop computer and keep it No talking while lecture

### 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

### Chapter 8: Conservation of Energy

Chapter 8: Conservation of Energy This chapter actually completes the argument established in the previous chapter and outlines the standing concepts of energy and conservative rules of total energy. I

### 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

### Forces. -using a consistent system of units, such as the metric system, we can define force as:

Forces Force: -physical property which causes masses to accelerate (change of speed or direction) -a push or pull -vector possessing both a magnitude and a direction and adds according to the Parallelogram

### f max s = µ s N (5.1)

Chapter 5 Forces and Motion II 5.1 The Important Stuff 5.1.1 Friction Forces Forces which are known collectively as friction forces are all around us in daily life. In elementary physics we discuss the

### Review D: Potential Energy and the Conservation of Mechanical Energy

MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department o Physics 8. Review D: Potential Energy and the Conservation o Mechanical Energy D.1 Conservative and Non-conservative Force... D.1.1 Introduction... D.1.

### 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

### College Physics 140 Chapter 4: Force and Newton s Laws of Motion

College Physics 140 Chapter 4: Force and Newton s Laws of Motion We will be investigating what makes you move (forces) and how that accelerates objects. Chapter 4: Forces and Newton s Laws of Motion Forces

### 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

### 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

### PH2213 : Examples from Chapter 4 : Newton s Laws of Motion. Key Concepts

PH2213 : Examples from Chapter 4 : Newton s Laws of Motion Key Concepts Newton s First and Second Laws (basically Σ F = m a ) allow us to relate the forces acting on an object (left-hand side) to the motion

### AP Physics Newton's Laws Practice Test

AP Physics Newton's Laws Practice Test Answers: A,D,C,D,C,E,D,B,A,B,C,C,A,A 15. (b) both are 2.8 m/s 2 (c) 22.4 N (d) 1 s, 2.8 m/s 16. (a) 12.5 N, 3.54 m/s 2 (b) 5.3 kg 1. Two blocks are pushed along a

### Chapter 6: Momentum And Collisions. The linear momentum p of an object is the product of the object s mass m and velocity v

Chapter 6: Momentum And Collisions The linear momentum p o an object is the product o the object s mass m and velocity v r r p = mv Linear momentum is a vector quantity and has the same direction as the

### PHYSICS 149: Lecture 15

PHYSICS 149: Lecture 15 Chapter 6: Conservation of Energy 6.3 Kinetic Energy 6.4 Gravitational Potential Energy Lecture 15 Purdue University, Physics 149 1 ILQ 1 Mimas orbits Saturn at a distance D. Enceladus

### PHYSICS 111 HOMEWORK SOLUTION #10. April 8, 2013

PHYSICS HOMEWORK SOLUTION #0 April 8, 203 0. Find the net torque on the wheel in the figure below about the axle through O, taking a = 6.0 cm and b = 30.0 cm. A torque that s produced by a force can be

### 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

### 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

### 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

### Physics 1000 Final Examination. December A) 87 m B) 46 m C) 94 m D) 50 m

Answer all questions. The multiple choice questions are worth 4 marks and problems 10 marks each. 1. You walk 55 m to the north, then turn 60 to your right and walk another 45 m. How far are you from where

### Ch.4 Forces. Conceptual questions #1, 2, 12 Problem 1, 2, 5, 6, 7, 10, 12, 15, 16, 19, 20, 21, 23, 24, 26, 27, 30, 38, 39, 41, 42, 47, 50, 56, 66

Ch.4 Forces Conceptual questions #1, 2, 12 Problem 1, 2, 5, 6, 7, 10, 12, 15, 16, 19, 20, 21, 23, 24, 26, 27, 30, 38, 39, 41, 42, 47, 50, 56, 66 Forces Forces - vector quantity that changes the velocity

### PHY1 Review for Exam 5

Topics 1. Uniform circular Motion a. Centripetal acceleration b. Centripetal force c. Horizontal motion d. ertical motion e. Circular motion with an angle 2. Universal gravitation a. Gravitational force

### Supplemental Questions

Supplemental Questions The fastest of all fishes is the sailfish. If a sailfish accelerates at a rate of 14 (km/hr)/sec [fwd] for 4.7 s from its initial velocity of 42 km/h [fwd], what is its final velocity?

### 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

### THE NATURE OF FORCES Forces can be divided into two categories: contact forces and non-contact forces.

SESSION 2: NEWTON S LAWS Key Concepts In this session we Examine different types of forces Review and apply Newton's Laws of motion Use Newton's Law of Universal Gravitation to solve problems X-planation

### Chapter 4 - Forces and Newton s Laws of Motion w./ QuickCheck Questions

Chapter 4 - Forces and Newton s Laws of Motion w./ QuickCheck Questions 2015 Pearson Education, Inc. Anastasia Ierides Department of Physics and Astronomy University of New Mexico September 8, 2015 Review

### 9 ROTATIONAL DYNAMICS

CHAPTER 9 ROTATIONAL DYNAMICS CONCEPTUAL QUESTIONS 1. REASONING AND SOLUTION The magnitude of the torque produced by a force F is given by τ = Fl, where l is the lever arm. When a long pipe is slipped

### Physics 101 Exam 1 NAME 2/7

Physics 101 Exam 1 NAME 2/7 1 In the situation below, a person pulls a string attached to block A, which is in turn attached to another, heavier block B via a second string (a) Which block has the larger

### Physics Midterm Review. Multiple-Choice Questions

Physics Midterm Review Multiple-Choice Questions 1. A train moves at a constant velocity of 90 km/h. How far will it move in 0.25 h? A. 10 km B. 22.5 km C. 25 km D. 45 km E. 50 km 2. A bicyclist moves

### Clicker Question. A tractor driving at a constant speed pulls a sled loaded with firewood. There is friction between the sled and the road.

A tractor driving at a constant speed pulls a sled loaded with firewood. There is friction between the sled and the road. A. positive. B. negative. C. zero. Clicker Question The total work done on the

### Chapter 3.8 & 6 Solutions

Chapter 3.8 & 6 Solutions P3.37. Prepare: We are asked to find period, speed and acceleration. Period and frequency are inverses according to Equation 3.26. To find speed we need to know the distance traveled

### Lesson 04: Newton s laws of motion

www.scimsacademy.com Lesson 04: Newton s laws of motion If you are not familiar with the basics of calculus and vectors, please read our freely available lessons on these topics, before reading this lesson.

### 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

### 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

### Homework 4. problems: 5.61, 5.67, 6.63, 13.21

Homework 4 problems: 5.6, 5.67, 6.6,. Problem 5.6 An object of mass M is held in place by an applied force F. and a pulley system as shown in the figure. he pulleys are massless and frictionless. Find

### 356 CHAPTER 12 Bob Daemmrich

Standard 7.3.17: Investigate that an unbalanced force, acting on an object, changes its speed or path of motion or both, and know that if the force always acts toward the same center as the object moves,

### Physics 100 prac exam2

Physics 100 prac exam2 Student: 1. Earth's gravity attracts a person with a force of 120 lbs. The force with which the Earth is attracted towards the person is B. small but not zero. C. billions and billions

### 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

### Chapter 6: Energy and Oscillations. 1. Which of the following is not an energy unit? A. N m B. Joule C. calorie D. watt E.

Chapter 6: Energy and Oscillations 1. Which of the following is not an energy unit? A. N m B. Joule C. calorie D. watt E. kwh 2. Work is not being done on an object unless the A. net force on the object

### Rotational Mechanics - 1

Rotational Mechanics - 1 The Radian The radian is a unit of angular measure. The radian can be defined as the arc length s along a circle divided by the radius r. s r Comparing degrees and radians 360

### 1 of 9 10/27/2009 7:46 PM

1 of 9 10/27/2009 7:46 PM Chapter 11 Homework Due: 9:00am on Tuesday, October 27, 2009 Note: To understand how points are awarded, read your instructor's Grading Policy [Return to Standard Assignment View]

### F mg (10.1 kg)(9.80 m/s ) m

Week 9 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

### Assignment Work (Physics) Class :Xi Chapter :04: Motion In PLANE

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Assignment Work (Physics) Class :Xi Chapter :04: Motion In PLANE State law of parallelogram of vector addition and derive expression for resultant of two vectors

### Name: Date: PRACTICE QUESTIONS PHYSICS 201 FALL 2009 EXAM 2

Name: Date: PRACTICE QUESTIONS PHYSICS 201 FALL 2009 EXAM 2 1. A force accelerates a body of mass M. The same force applied to a second body produces three times the acceleration. What is the mass of the

### Potential and Kinetic Energy: The Roller Coaster Lab Student Advanced Version

Potential and Kinetic Energy: The Roller Coaster Lab Student Advanced Version Key Concepts: Energy is the ability of a system or object to perform work. It exists in various forms. Potential Energy is

### Conceptual: 1, 3, 5, 6, 8, 16, 18, 19. Problems: 4, 6, 8, 11, 16, 20, 23, 27, 34, 41, 45, 56, 60, 65. Conceptual Questions

Conceptual: 1, 3, 5, 6, 8, 16, 18, 19 Problems: 4, 6, 8, 11, 16, 20, 23, 27, 34, 41, 45, 56, 60, 65 Conceptual Questions 1. The magnetic field cannot be described as the magnetic force per unit charge

### 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

### Chapter 07: Kinetic Energy and Work

Chapter 07: Kinetic Energy and Work Conservation of Energy is one of Nature s fundamental laws that is not violated. Energy can take on different forms in a given system. This chapter we will discuss work

### Newton s Laws of Motion

Physics Newton s Laws of Motion Newton s Laws of Motion 4.1 Objectives Explain Newton s first law of motion. Explain Newton s second law of motion. Explain Newton s third law of motion. Solve problems

### Forces & Newton s Laws. Teacher Packet

AP * PHYSICS B Forces & Newton s Laws eacher Packet AP* is a trademark of the College Entrance Examination Board. he College Entrance Examination Board was not involved in the production of this material.

### 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

### 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

### 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

### Physics-1 Recitation-3

Physics-1 Recitation-3 The Laws of Motion 1) The displacement of a 2 kg particle is given by x = At 3/2. In here, A is 6.0 m/s 3/2. Find the net force acting on the particle. (Note that the force is time

### Mechanics 2. Revision Notes

Mechanics 2 Revision Notes November 2012 Contents 1 Kinematics 3 Constant acceleration in a vertical plane... 3 Variable acceleration... 5 Using vectors... 6 2 Centres of mass 8 Centre of mass of n particles...

### Chapter 5 Force and Motion I

Chapter 5 orce and Motion I I. ewton s irst law. II. ewton s second law. III. Particular orces: -Gravitational - Weight -ormal -riction - ension IV. ewton s third law. ewton mechanics laws cannot be applied

### 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

### 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

### Ch 6 Forces. Question: 9 Problems: 3, 5, 13, 23, 29, 31, 37, 41, 45, 47, 55, 79

Ch 6 Forces Question: 9 Problems: 3, 5, 13, 23, 29, 31, 37, 41, 45, 47, 55, 79 Friction When is friction present in ordinary life? - car brakes - driving around a turn - walking - rubbing your hands together

### Newton s Laws of Motion

Chapter 4 Newton s Laws of Motion PowerPoint Lectures for University Physics, Twelfth Edition Hugh D. Young and Roger A. Freedman Lectures by James Pazun Modified by P. Lam 7_8_2016 Goals for Chapter 4

### 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

### Newton s Third Law. object 1 on object 2 is equal in magnitude and opposite in direction to the force exerted by object 2 on object 1

Newton s Third Law! If two objects interact, the force exerted by object 1 on object 2 is equal in magnitude and opposite in direction to the force exerted by object 2 on object 1!! Note on notation: is

### 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

### 2015 Pearson Education, Inc. Section 24.5 Magnetic Fields Exert Forces on Moving Charges

Section 24.5 Magnetic Fields Exert Forces on Moving Charges Magnetic Fields Sources of Magnetic Fields You already know that a moving charge is the creator of a magnetic field. Effects of Magnetic Fields

### 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

### Physics 101 Prof. Ekey. Chapter 5 Force and motion (Newton, vectors and causing commotion)

Physics 101 Prof. Ekey Chapter 5 Force and motion (Newton, vectors and causing commotion) Goal of chapter 5 is to establish a connection between force and motion This should feel like chapter 1 Questions

### End-of-Chapter Exercises

End-of-Chapter Exercises Exercises 1 12 are conceptual questions that are designed to see if you have understood the main concepts of the chapter. 1. Figure 11.20 shows four different cases involving a