Momentum Name

AP Physics B Unit 2 Test – Dynamics/Work/Energy/Momentum Name ______________ 1. The term "mass" refers to the same physical concept as: A) weight B...
Author: Maria Spencer
18 downloads 2 Views 90KB Size
AP Physics B

Unit 2 Test – Dynamics/Work/Energy/Momentum

Name ______________

1. The term "mass" refers to the same physical concept as: A) weight B) inertia C) force D) acceleration E) volume 2. When a certain force is applied to the 1-kg standard mass its acceleration is 5.0 m/s2. When the same force is applied to another object its acceleration is one-fifth as much. The mass of the object is: A) 0.2 kg B) 0.5 kg C) 1.0 kg D) 5.0 kg E) 10 kg 3. The mass of a body: A) is slightly different at different places on the Earth B) is a vector C) is independent of the acceleration due to gravity D) is the same for all bodies of the same volume E) can be measured most accurately on a spring scale 4. Two forces, one with a magnitude of 3 N and the other with a magnitude of 5 N, are applied to an object. For which orientations of the forces shown in the diagrams is the magnitude of the acceleration of the object the least?

A) B) C) D) E)

I II III IV V

Page 1

5. A heavy wooden block is dragged by a force ¢ along a rough steel plate, as shown below for two cases. The magnitude of the applied force ¢ is the same for both cases. The normal force in (ii), as compared with the normal force in (i) is:

A) B) C) D) E)

the same greater less less for some angles of the incline and greater for others less or greater, depending on the magnitude of the applied force ¢.

6. A circus performer of weight W is walking along a "high wire" as shown. The tension in the wire is:

A) B) C) D) E)

approximately W approximately W/2 much less than W much more than W depends on whether he stands on one or two feet

7. A 1000-kg elevator is rising and its speed is increasing at 3 m/s2. The tension in the elevator cable is: A) 6800 N B) 1000 N C) 3000 N D) 9800 N E) 12800 N 8. A physics textbook is suspended on a spring scale in an elevator. Of the following, the scale shows the highest reading when the elevator: A) moves upward with increasing speed B) moves upward with decreasing speed C) remains stationary D) moves downward with increasing speed E) moves downward at constant speed Page 2

9. A book rests on a table, exerting a downward force on the table. The reaction to this force is: A) the force of the Earth on the book B) the force of the table on the book C) the force of the Earth on the table D) the force of the book on the Earth E) the inertia of the book 10. A 70 N block and an 35-N block are connected by a string as shown. If the pulley is massless and the surface is frictionless, the magnitude of the acceleration of the 70-N block (in m/s2) is:

A) B) C) D) E)

1.6 m/s2 3.3 m/s2 4.9 m/s2 6.7 m/s2 9.8 m/s2

11. A forward force of 12 N is used to pull a 240-N sled at constant velocity on a frozen pond. The coefficient of friction is: A) 0.5 B) 0.05 C) 2 D) 0.2 E) 20

Page 3

12. A boy pulls a wooden box along a rough horizontal floor at constant speed by means of a force § as shown. In the diagram f is the magnitude of the force of friction, N is the magnitude of the normal force, and Fg is the magnitude of the force of gravity. Which of the following must be true?

A) B) C) D) E)

P = f and N = Fg P = f and N > Fg P > f and N < Fg P > f and N = Fg none of these

13. A block is first placed on its long side and then on its short side on the same inclined plane. The block slides down the plane on its short side but remains at rest on its long side. A possible explanation is:

A) B) C) D) E)

the short side is smoother the frictional force is less because the contact area is less the center of gravity is higher in the second case the normal force is less in the second case the force of gravity is more nearly down the plane in the second case

14. Why do raindrops fall with constant speed during the later stages of their descent? A) The gravitational force is the same for all drops B) Air resistance just balances the force of gravity C) The drops all fall from the same height D) The force of gravity is negligible for objects as small as raindrops E) Gravity cannot increase the speed of a falling object to more than 32 ft/s 15. A fly ball to left field is caught at the same height as it was originally hit. Over its entire flight the work done by gravity and the work done by air resistance, respectively, are: A) zero; positive B) zero; negative C) positive; negative D) negative; positive Page 4

E) negative; negative

16. Which of the following bodies has the largest kinetic energy? A) Mass 3M and speed V B) Mass 3M and speed 2V C) Mass 2M and speed 3V D) Mass M and speed 4V E) All four of the above have the same kinetic energy 17. A Boston Red Sox baseball player catches a ball of mass m that is moving toward him with speed v. While bringing the ball to rest, his hand moves back a distance d. Assuming constant deceleration, the horizontal force exerted on the ball by his hand is: A) mv/d B) mvd C) mv2/d D) 2mv/d E) mv2/(2d) 18. In raising an object to a given height by means of an inclined plane, as compared with raising the object vertically, there is a reduction in: A) work required B) distance pushed C) friction D) force required E) value of the acceleration due to gravity 19. A woman lifts a barbell 2.0 m in 5.0 s. If she lifts it the same distance in 10 s, the work done by her is: A) four times as great B) two times as great C) the same D) half as great E) one-fourth as great 20. Momentum may be expressed in: A) kg/m B) gram s C) N s D) kg/(m s) E) N/s 21. The momentum of an object at a given instant is independent of its: A) inertia B) mass C) speed D) velocity Page 5

E) acceleration

22. A particle moves along the x axis. Its momentum is graphed below as a function of time. Rank the numbered regions according to the magnitude of the force acting on the particle, least to greatest.

A) B) C) D) E)

1, 2, 3, 4 2, 3, 4, 1 1, 4, 3, 2 1, 3, 4, 2 2, 4, 3, 1

23. A man, standing at rest on a horizontal frictionless floor, might get himself moving by: A) walking B) rolling C) exhaling vertically D) crawling slowly E) throwing a shoe horizontally 24. A rifle of mass M is initially at rest but free to recoil. It fires a bullet of mass m and velocity v (relative to the ground). After firing, the velocity of the rifle (relative to the ground) is: A) –mv B) –Mv/m C) –mv/M D) –v E) mv/M

Page 6

25. A 5-kg object can move along the x axis. It is subjected to a force ¢ in the positive x direction; a graph of F as a function of time t is shown below. Over the time the force is applied the change in the velocity of the object is:

A) B) C) D) E)

0.8 m/s 1.1 m/s 1.6 m/s 2.3 m/s 4.0 m/s

26. Why does a rocket accelerate when it is fired horizontally? A) Exhaust gases push against outside air B) Exhaust gases, which the rocket pushes backwards, push the rocket forward C) Outside air exerts more force on the back of the rocket than on the front D) Exhaust speed is greater than the rocket speed E) Atmospheric pressure at the back of the rocket is reduced 27. A 2-kg object is acted upon by a single force in the x direction in a manner described by the graph shown. The momentum acquired by the object is:

A) B) C) D) E)

16 N 30 N 32 N 40 N 48 N

s s s s s

28. An elastic collision is one in which: A) momentum is not conserved but kinetic energy is conserved B) total mass is not conserved but momentum is conserved Page 7

C) kinetic energy and momentum are both conserved D) momentum is conserved but kinetic energy is not conserved E) the total impulse is equal to the change in kinetic energy 29. A projectile in flight explodes into several fragments. The total momentum of the fragments immediately after this explosion: A) is the same as the momentum of the projectile immediately before the explosion B) has been changed into kinetic energy of the fragments C) is less than the momentum of the projectile immediately before the explosion D) is more than the momentum of the projectile immediately before the explosion E) has been changed into radiant energy

END OF MULTIPLE CHOICE SECTION Answer Key 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29.

B D C A C D E A B B B A A B B C E D C C E B E C A B A C A

Page 8