Ch. 12 Review Game

Review force, Newton’s Laws of Motion, and universal forces.

Short Answer46. What is the direction of the net force on a falling sky diver before she

reaches terminal velocity? After she is falling at terminal velocity?- down, there is no net force on the sky diver47. How can you double the acceleration of an object if you cannot alter

the object’s mass?- Double the net force acting on the object48. Why don’t action-reaction forces cancel each other?- The action force and the reaction force act on different objects. For

forces to cancel, they must act on the same object49. One end of a bar magnet attracts one end of a second bar magnet.

What will happen if the second bar magnet is reversed?- The ends of the bar magnet will now repel each other50. What is the primary cause of Earth’s ocean tides?- The gravitational pull of the moon

Problem51. A tow truck exerts a net horizontal force of 1050 N on an 760-kilogram car. What is

the acceleration of the car during this time? Show your work. (Acceleration = net force/mass)

1050N/760kg= 1.4kgm/s2= 1.4m/s2

kg

52. The mass of a newborn baby is 3.5 kilograms. What is the baby’s weight? (The acceleration due to gravity at Earth’s surface is 9.8 m/s2.) Show your work. (Weight = Mass x Acceleration due to gravity)

3.5kg x 9.8m/s2=34.3kg x m/s2 = 34.3N53. A 38-kilogram canoe broke free of its dock and is now floating downriver at a speed

of 2.2 m/s. What is the canoe’s momentum? Show your work. (Momentum = Mass Velocity)

38kg x 2.2m/s= 83.6 kgx m/s, downriver54. A small engine causes a 0.3-kg model airplane to accelerate at a rate of 11 m/s2.

What is the net force on the model airplane? Show your work (a = F/m )0.3kg x 11 m/s2= 3.3 kg x m/s2 = 3.3 N

Essay55. Why does a biker have to pedal harder to travel at a

constant speed into the wind on a windy day compared to traveling on the same road at the same speed on a calm day?

- On both the calm and windy days, the net force on the biker is zero because the biker is traveling at constant speed. On a calm day, the biker must pedal so that the forward-directed force applied to the bike balances the forces of friction opposing the forward motion. The friction forces primarily take the form rolling friction and fluid friction. On a windy day, the fluid friction force is much greater, so the rider must pedal harder to maintain the same constant speed.

OtherFigure 12-2

56. Interpreting Graphics In Figure 12-2, what is the direction of the centripetal force acting on the satellite at this location in its orbit?

D57. Applying Concepts The centripetal force acting on the

satellite in Figure 12-2 is one of a pair of action-reaction forces. On what object is the other force in the pair acting?

Earth

OtherFigure 12-3

58. Interpreting Graphics In Figure 12-3, what is the momentum of each skater at Time 1?

0 kg x m/s59. Comparing and Contrasting In Figure 12-3, compare the size and direction of the

momentums of both skaters immediately after the push shown at Time 2.Equal size, opposite direction60. Applying Concepts Suppose that the skaters repeat the demonstration in Figure 12-3

again. This time Skater B is holding a 10-kilogram mass. If Skater A pushes exactly as he did the first time, will Skater A’s motion be different this time? Explain your answer.

No; Skater A is exerting the same force on Skater B as before and so Skater B is exerting the same force on Skater A as before. The result is that Skater’s A motion will be the same.

Multiple Choice ____ 1. The SI unit of force is thea. joule. c. meter.b. kilogram. d. newton.d. newton____ 2. Which of the following relationships is correct?a. 1 N = 1 kg c. 1 N = 1 kg·m/sb. 1 N = 1 kg·m d. 1 N = 1 kg·m/s2

d. 1 N = 1 kg·m/s2

____ 3. When an unbalanced force acts on an object,a. the object’s motion does not change. c. the weight of the object decreases.b. the object accelerates. d. the inertia of the object increases.b. the object accelerates.____ 4. When a pair of balanced forces acts on an object, the net force that results isa. greater in size than both forces combined. b. greater in size than one of the forces.c. equal in size to one of the forces. d. equal to zero.d. equal to zero.____ 5. What kind of friction occurs as a fish swims through water?a. Fluid c. slidingb. Rolling d. statica. Fluid

____ 6. As you push a cereal box across a tabletop, the sliding friction acting on the cereal boxa. acts in the direction of motion. b. equals the weight of the box.c. is usually greater than static friction. d. acts in the direction opposite of motion.d. acts in the direction opposite of motion.____ 7. The forces acting on a falling leaf area. air resistance and fluid friction. c. gravity and static friction.b. gravity and air resistance. d. weight and rolling frictionb. gravity and air resistance.

____ 8. Figure 12-1 shows the motion of three balls. The curved paths followed by balls B and C are examples of

a. centripetal motion. c. linear motion.b. constant motion. d. projectile motion.d. projectile motion.____ 9. Projectile motion is caused bya. the downward force of gravity. b. an initial forward velocity.c. a final vertical velocity. d. the downward force of gravity and an initial forward velocity.d. the downward force of gravity and an initial forward velocity.____ 10. The property of matter that resists changes in motion is calleda. friction. c. inertia.b. gravity. d. weight.c. inertia.

____ 11. An orange might roll off your cafeteria tray when you stop suddenly because ofa. the balanced forces acting on the orange. b. the centripetal force acting on the

orange.c. the friction forces acting on the orange. d. the orange’s inertia.d. the orange’s inertia.____ 12. According to Newton’s second law of motion, the acceleration of an object equals

the net force acting on the object divided by the object’sa. mass. c. velocity.b. momentum. d. weight.a. mass.____ 13. If a force of 12 N is applied to an object with a mass of 2 kg, the object will

accelerate ata.0.17 m/s2. c.6 m/s2.b.24 m/s2. d.12 m/s2.c.6 m/s2.____ 14. Your weight equals youra. mass. b. mass divided by the net force acting on you.c. mass times the acceleration due to gravity. d. mass times your speed.c. mass times the acceleration due to gravity.____ 15. Newton’s third law of motion describesa. action and reaction forces. c. centripetal forces.b. balanced forces. d.net force.a. action and reaction forces.

____ 16. In which of the following are action and reaction forces involved?a. when a tennis racket strikes a tennis ball b. when stepping from a curbc. when rowing a boat d. all of the aboved. all of the above____ 17. What is the momentum of a 50-kilogram ice skater gliding across the ice at a speed

of 5 m/s?a.10 c.50 kgb.500 kg·m/s d.250 kg·m/sd.250 kg·m/s____ 18. What force is responsible for the repulsion between two positively-charged

particles?a. Centripetal c. gravitationalb. Electric d. nuclearb. Electric____ 19. Which universal force acts only on the protons and neutrons in a nucleus?a. Electric c. magneticb. Gravitational d. strong nucleard. strong nuclear____ 20. With which of the following is the weak nuclear force associated?a. Lightning c. ocean tidesb. nuclear decay d. static cling b. nuclear decay

____ 21. Which of the following universal forces is the weakest?a. Electric c. magneticb. Gravitational d. strong nuclearb. Gravitational____ 22. As an astronaut travels far away from Earth, her weighta. decreases because gravity decreases. b. decreases because her mass decreases.c. Increases because gravity increases. d. remains the same because her mass

remains the same.a. decreases because gravity decreases.____ 23. The gravitational force between two objects increases as massa. decreases or distance decreases. c. Increases or distance decreases.b. decreases or distance increases. d. increases or distance increases.c. Increases or distance decreases.____ 24. The force that keeps an object moving in a circle is calleda. centripetal force. c. Inertia.b. fluid friction. d. momentum.a. centripetal force.____ 25. The centripetal force acting on a satellite in orbita. acts as an unbalanced force on the satellite. b. changes the direction of the satellite. c. is a center-directed force. d. all of the aboved. all of the above

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