Physics Final Practice Exam - Part 2

Transcription

1 Physics Final Practice Exam - Part 2 Multiple Choice. Identify the choice that best completes the statement or answers the question. 1. An object has a constant mass. A constant force on the object produces constant a. velocity. c. both A and B b. acceleration. d. none of the above 2. A jumbo jet cruises at a constant velocity when the total thrust of the engines on the jet is 50,000 N. How much air resistance acts on the jet? a. 0 N d. 75,000 N b. 25,000 N e. 100,000 N c. 50,000 N 3. If a truck has ten times the mass of a car and the two vehicles are pushed with an equal force, you would expect the acceleration of the truck to be a. times that of the car. c. 10 times that of the car. d. 100 times that of the car. b. times that of the car. 4. A player hits a ball with a bat. The action force is the impact of the bat against the ball. What is the reaction to this force? a. The force of the ball against the bat d. The grip of the player's hand against the bat b. The weight of the ball e. none of the above c. Air resistance on the ball 5. A large truck and a small car traveling at the same speed have a head-on collision. The vehicle to undergo the greater change in velocity will be a. the small car. c. neither both are the same b. the large truck. 6. As a 600-N woman sits on the floor, the floor exerts a force on her of a. 6 N. d. 600 N. b. 60 N. e N. c N. 7. Suppose two people, one having three times the mass of the other, pull on opposite sides of a 20-meter rope while on frictionless ice. After a brief time, they meet. The more massive person slides a distance of a. 4 m. c. 6 m. b. 5 m. d. 7 m. 8. If your car runs out of gas, why can t you push on the car s windshield from the inside to move it? a. In order for the car to move, a force must be exerted by you on the car s windshield. b. In order for the car to move, a force must be exerted by the car s windshield on you. c. In order for the car to move, an outside force must be exerted on the car. d. In order for the car to move, a force must be exerted by the car on the ground. 9. In order to increase the final momentum of a golf ball, we could a. increase the force acting on it. d. swing as hard as possible. b. follow through when hitting the ball. e. all of the above c. increase the time of contact with the ball.

2 10. Momentum of a system is conserved only when a. there are no internal forces acting on the system. b. the system is not moving. c. there are no forces acting on the system. d. there is no net external force acting on the system. e. the system has zero momentum. 11. A freight train rolls along a track with considerable momentum. If it were to roll at the same speed but had twice as much mass, its momentum would be a. zero. c. quadrupled. b. unchanged. d. doubled. 12. Suppose a cannon is made of a strong but very light material. Suppose also that the cannonball is more massive than the cannon itself. For such a system a. conservation of momentum would not hold. b. conservation of energy would not hold. c. the target would be a safer place than where the operator is located. d. the force on the cannonball would be greater than the force on the cannon. e. recoil problems would be lessened. 13. When you jump off a step, you usually bend your knees as you reach the ground. By doing this, the time of the impact is about 10 times more what it would be in a stiff-legged landing, and the average force on your body is reduced by a. less than 10 times. c. more than 10 times. b. about 10 times. 14. What is the direction of the force that acts on clothes in the spin cycle of a washing machine? a. Inward c. Outward b. Down d. Up 15. If you try to touch your toes while standing flat against a wall, you probably will fall over. The reason this happens is that a. your center of gravity is not located directly above your support area. b. your center of gravity is outside your support area. c. both A and B 16. Two people sit on a balanced seesaw. When one person leans toward the center of the seesaw, that person's end of the seesaw will _. a. fall c. stay at the same level b. rise 17. A ring and a disk roll down a hill together. Which reaches the bottom first? a. Both reach the bottom at the same time d. Depends on the masses b. Depends on the moments of inertia e. The ring c. The disk 18. A good explanation of why a ball gains speed as it rolls down an incline involves the _. a. force that acts on it d. concentrated rotational inertia of the ball b. friction between it and the incline e. all of the above c. torque that acts on it 19. A ring, a disk, and a solid ball having equal masses roll down a hill at the same time. Which reaches the bottom first? a. Depends on what each is made of. d. Depends on the radius of each. b. The disk e. The ball c. The ring

3 20. Newton hypothesized that the moon _. a. is a projectile b. is falling around Earth c. has tangential velocity that prevents it from falling into Earth d. is actually attracted to Earth e. all of the above 21. If the radius of Earth decreased, with no change in mass, your weight would _. a. not change c. decrease b. increase 22. A planet has half the mass of the Earth and half the radius. Compared to its weight on Earth, an apple on this planet would weigh _. a. twice as much d. the same b. one-fourth as much e. zero c. half as much 23. The amount of potential energy possessed by an elevated object is equal to a. the power used to lift it. d. the work done in lifting it. b. the distance it is lifted. e. the value of the acceleration due to gravity. c. the force needed to lift it. 24. When a car s speed triples, its kinetic energy a. remains the same. b. triples. c. increases by four times. d. increases by nine times. e. none of the above 25. The ratio of output force to input force of a simple machine is called the a. fulcrum. d. lever arm. b. efficiency. e. mechanical advantage. c. pivot point. 26. How many joules of work are done on a box when a force of 25 N pushes it 3 m? a. 1 J d. 25 J b. 3 J e. 75 J c. 8 J 27. How much work is done on a 60-N box of books that you carry horizontally across a 6-m room? a. 0 J d. 60 J b. 6 J e. 360 J c. 10 J 28. It takes 80 J to push a large box 8 m across a floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box? a. 8 N d. 640 N b. 10 N e. none of the above c. 80 N

4 Essay. Use complete sentences to answer the questions below. 29. Discuss the difference between linear speed and rotational speed. Where does a ladybug sitting on a rotating record have the greatest linear speed? The greatest rotational speed? What kind of speed would she have at the center? Problems. Show all work including the correct units and sig figs with your answer. 30. You push with 10.0 N on a 5.0-kg block and there are no opposing forces. How fast will the block accelerate? 31. Suppose that you exert 300 N horizontally on a 50-kg crate on a factory floor, where friction between the crate and the floor is 100 N. What is the acceleration of the crate? 32. A cement truck of mass 16,000 kg moving at 15 m/s slams into a cement wall and comes to a halt in 0.75 seconds. What is the average force of impact on the truck? 33. A biker is travelling 5.75 m/s at the top of the hill. He coasts down the hill. What is his speed at the bottom of the hill? The hill is 255 meters long and has a constant slope of 3.00 degrees. Assume the friction forces, rotational inertia and air resistance are negligible. The bike and biker have a mass of 80.0 kg. 34. A 125kg satellite orbits 525 km above the earth s surface. What is the centripetal force acting on the satellite?

5 35. A 1.20 kg ball is tied to a 1.70 meter string. What is the tangential velocity of the ball if the tension on the string is 36.5 N? 36. What is the period of the ball in the previous problem? 37. A 50-kg cart moving at 100 km/h collides head-on with an approaching 50-kg cart moving at 10 km/h (in the opposite direction). If the two carts stick together, what will be their speed? 38. Consider a long uniform wooden plank of weight W resting on a table. How much weight needs to be placed at the end of the plank resting on the table in order to prevent toppling if 70% of the plank extends beyond the edge? 39. A ball at the end of a 5.0 meter rope is swung in a horizontal circular path. It has a tangential velocity of 5.0 m/s. The rope is then pulled in so that the radius of the path is the ball? For a small object at the end of a long rope, I = mr as big. What is the new tangential velocity of 40. Imagine you are standing atop a ladder so tall that you are 2 Earth radii from Earth's center. What is your weight at the top of the ladder, relative to your weight on the ground?

6 Physics Final Practice Exam - Part 2 Answer Section MULTIPLE CHOICE 1. ANS: B PTS: 1 DIF: L2 OBJ: 6.3 Newton's Second Law of Motion STA: C.7 KEY: mass acceleration 2. ANS: C PTS: 1 DIF: L2 OBJ: 6.3 Newton's Second Law of Motion STA: C.7 KEY: velocity resistance 3. ANS: B PTS: 1 DIF: L2 OBJ: 6.2 Mass Resists Acceleration STA: C.7 KEY: mass acceleration inversely 4. ANS: A PTS: 1 DIF: L2 OBJ: 7.3 Identifying Action and Reaction STA: C.7 S11.A KEY: action force reaction 5. ANS: A PTS: 1 DIF: L2 OBJ: 7.3 Identifying Action and Reaction STA: C.7 S11.A KEY: collision velocity mass 6. ANS: D PTS: 1 DIF: L2 OBJ: 7.2 Newton's Third Law KEY: weight force 7. ANS: B PTS: 1 DIF: L2 OBJ: 7.3 Identifying Action and Reaction STA: C.7 S11.A KEY: mass force distance 8. ANS: D PTS: 1 DIF: L2 OBJ: 7.6 The Horse-Cart Problem STA: E C.7 KEY: Newton's third law force 9. ANS: E PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes Momentum STA: C.3 S11.A KEY: momentum force 10. ANS: D PTS: 1 DIF: L1 OBJ: 8.4 Conservation of Momentum STA: B.4 S11.A S11.A KEY: momentum conserve BLM: knowledge 11. ANS: D PTS: 1 DIF: L2 OBJ: 8.1 Momentum STA: C.3 S11.A KEY: momentum mass 12. ANS: C PTS: 1 DIF: L2 OBJ: 8.4 Conservation of Momentum STA: B.4 S11.A S11.A KEY: mass recoil 13. ANS: B PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes Momentum STA: C.3 S11.A KEY: force impact 14. ANS: A PTS: 1 DIF: L2 OBJ: 10.3 Centripetal Force S11.A S11.A KEY: force direction 15. ANS: A PTS: 1 DIF: L2 OBJ: 11.4 Center of Gravity STA: C.7 KEY: center gravity

7 16. ANS: B PTS: 1 DIF: L2 OBJ: 11.2 Balanced Torques KEY: lever seesaw 17. ANS: C PTS: 1 DIF: L2 OBJ: 12.1 Rotational Inertia KEY: solid hollow roll 18. ANS: E PTS: 1 DIF: L2 OBJ: 12.1 Rotational Inertia KEY: inertia force incline 19. ANS: E PTS: 1 DIF: L2 OBJ: 12.1 Rotational Inertia KEY: incline acceleration 20. ANS: E PTS: 1 DIF: L1 OBJ: 13.2 The Falling Moon STA: C.3 KEY: Newton moon BLM: knowledge 21. ANS: B PTS: 1 DIF: L2 OBJ: 13.5 Gravity and Distance:The Inverse-Square Law STA: C E.1 KEY: mass radius 22. ANS: A PTS: 1 DIF: L2 OBJ: 13.5 Gravity and Distance:The Inverse-Square Law STA: C E.1 KEY: mass radius weight 23. ANS: D PTS: 1 DIF: L1 OBJ: 9.4 Potential Energy KEY: potential energy BLM: knowledge 24. ANS: D PTS: 1 DIF: L2 OBJ: 9.5 Kinetic Energy STA: E.1 KEY: speed kinetic 25. ANS: E PTS: 1 DIF: L1 OBJ: 9.7 Conservation of Energy STA: C.2 S11.A S11.A.3.1 S11.A KEY: output input machine BLM: knowledge 26. ANS: E PTS: 1 DIF: L2 OBJ: 9.1 Work KEY: joule work force 27. ANS: A PTS: 1 DIF: L2 OBJ: 9.1 Work KEY: work distance 28. ANS: B PTS: 1 DIF: L2 OBJ: 9.1 Work KEY: force joule magnitude ESSAY 29. ANS: Linear speed is distance an object moves per unit time, whereas rotational speed is angle an object rotates per unit time. The ladybug will have the greatest linear speed at the edge of the record, but its rotational speed will be the same anywhere on the record. At the center of the record the ladybug has no linear speed, only rotational speed, as she rotates about her own and the record's axis. PTS: 1 DIF: L2 OBJ: 10.2 Rotational Speed STA: C.3 S11.A S11.A.2.1 S11.A.2.2 KEY: speed linear rotational PROBLEM

8 30. ANS: 2.0 m/s 2 PTS: 1 DIF: L2 OBJ: 6.3 Newton's Second Law of Motion STA: C.7 KEY: force acceleration 31. ANS: 4 m/s 2 PTS: 1 DIF: L2 OBJ: 6.7 Falling and Air Resistance STA: C.2 S11.A KEY: force friction acceleration 32. ANS: PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes Momentum STA: C.3 S11.A KEY: impact 33. ANS: Mechanical energy is conserved, so the total mechanical energy at the top of the hill is equal to the total mechanical energy at the bottom of the hill. At the top of the hill the mechanical energy is stored as kinetic energy and gravitational potential energy. At the bottom fo the hill the mechancial energy is all kinetic. PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes Momentum STA: C.3 S11.A KEY: impact 34. ANS: Gravity is the source of the centripetal force. PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes Momentum STA: C.3 S11.A KEY: impact 35. ANS: rearranging PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes Momentum STA: C.3 S11.A KEY: impact 36. ANS:

9 PTS: 1 DIF: L2 OBJ: 8.2 Impulse Changes Momentum STA: C.3 S11.A KEY: impact 37. ANS: 45.0 km/h PTS: 1 DIF: L2 OBJ: 8.5 Collisions STA: C.3 KEY: speed collision 38. ANS:. PTS: 1 DIF: L2 OBJ: 11.2 Balanced Torques KEY: weight gravity 39. ANS: increases by a factor of 2 PTS: 1 DIF: L2 OBJ: 12.1 Rotational Inertia KEY: circular tangent speed 40. ANS: 1 4 as much PTS: 1 DIF: L2 OBJ: 13.5 Gravity and Distance:The Inverse-Square Law STA: C E.1 KEY: radius weight