PSI AP Physics C – Dynamics

Multiple Choice Questions

1. After firing a cannon ball, the cannon moves in the opposite direction from the ball.

This an example of:

(A)Newton’s First Law

(B)Newton’s Second Law

(C)Newton’s Third Law

(D)Newton’s Law of Gravitation

(E)None of the above

2. In the absence of an external force a moving object will

(A) slow down and come to a stop

(B) speed up

(C) move with a constant speed in a straight line

(D) turn to the right

(E) turn to the left

3. A loaded truck collides with a car causing a large amount of damage to the car. Which

of the following is true about the collision?

(A)The force on the truck is greater than the force on the car.

(B)The force on the car is greater than the force on the truck.

(C)The force on the truck is the same in magnitude as the force on the car.

(D)During the collision, the truck has a greater displacement than the car.

(E)During the collision, the truck has a greater acceleration than the car.

4. An object is thrown straight up. How do we compare the net force on the object to its

weight when it is at the highest point in the path?

(A)It is greater than the weight

(B)It is slightly less than the weight

(C)It is zero

(D)It is equal to the weight

(E)It can’t be determined

5. An elevator car weighs 5500 N. If the car accelerates upwards at a rate of 4.0 m/s2,

what is the tension in the support cable lifting the car? Use g = 10 m/s2.

(A) 1600 N

(B) 3300 N

(C) 4400 N

(D) 7700 N

(E) 8700 N

6. Which of the following diagrams best represents the gravitational force W, the frictional force f,

and the normal force N that act on the block sliding down the inclined plane as shown above?

A. B. C. D. E.

7. A block with a mass m = 5 kg slides down an inclined plane with an angle θ = 37°. The

block maintains a constant acceleration a = 5.6 m/s2. (sin37° = 0.6, cos37° = 0.8). The

coefficient of kinetic friction between the block and the inclined surface is 0.05. What is

the normal force on the block?

(A) 50 N

(B) 40 N

(C) 30 N

(D)20 N

(E) 10 N

8. A block with a mass m = 5 kg slides down an inclined plane with an angle θ = 37°. The

block maintains a constant acceleration a = 5.6 m/s2. (sin37° = 0.6, cos37° = 0.8). The

coefficient of kinetic friction between the block and the inclined surface is 0.05. What is

the friction force between the block and inclined plane?

(A) 2 N

(B) 5 N

(C) 6 N

(D) 30 N

(E) 40 N

9. The coefficient of static friction between the block and the inclined plane is 0.4 and

θ=250. The block is placed on the inclined plane. The block will:

(A) not move.

(B) start moving down the incline and then stop before it reaches the bottom of the

incline.

(C) start moving down the incline and continue to increase its velocity.

(D) start moving and increase its acceleration until it reaches the bottom of the

incline.

(E) start moving and then its acceleration will decrease.

10. A system of two blocks is accelerated by an applied force of magnitude F on the

frictionless horizontal surface. The tension in the string between the blocks is:

(A) 3F

(B) 5F

(C) 3/8 F

(D) 1/3 F

(E) 1/5 F

11. A student pulls a wooden box along a rough horizontal floor at constant speed by means

of a force P as shown to the right. Which of the following must be true?

(A) P > f and N < W.

(B) P > f and N = W.

(C) P = f and N > W.

(D) P = f and N = W.

(E) P < f and N = W.

12. As shown below, a boy pushes a sled of mass

m across a rough horizontal surface by

applying a force of magnitude F directed at

an angle . The normal force on the sled is:

(A) mg (B) mg sin (C) mg cos (D) mg + F sin (E) mg – F sin

13. A block of mass m is pulled along a horizontal surface

at constant speed v by a force Fapp , which acts at an

angle of with the horizontal. The normal force

exerted on the block by the surface is:

(A) mg - Fapp cos

(B) mg- Fapp sin

(C) mg

(D) mg + Fapp sin

(E) mg + Fapp cos

14. An ideal spring obeys Hooke's law, F = -kx. A mass of 0.30 kg hung vertically from this

spring stretches the spring 0.015 meter. The value of the spring constant is nearly

(A) 150 N/m

(B) 200 N/m

(C) 300 N/m

(D) 250 N/m

(E) 350 N/m

15. A block with a mass m is placed on the top of an identical

block m and the system of two blocks is at rest on a rough

horizontal surface as shown below. The top block is tied to

the wall. The coefficient of static friction between all

surfaces is µs. What maximum value does force F reach

before the lower block starts sliding to the left?

(A) 3 µsmg

(B) 2 µsmg

(C) 4 µsmg

(D) ½ µsmg

(E) ¼ µsmg

16. Three blocks connected with each other by two light strings. The blocks have different

masses m2 > m3 >m1. The heaviest of three blocks is placed on a frictionless table. The

system of three blocks is released from rest. What is the acceleration of block m2?

(A) (A)(m2 - m3 - m1)g/(m1 + m2 + m3)

(B) (B)(m1 - m3 - m2)g/(m1 + m2 + m3)

(C) (C)(m3 - m1)g/(m1 + m2 + m3)

(D) (D)(m3 - m2- m1)g/(m1 + m2 + m3)

(E) (E)(m1 - m3)g/(m1 + m2 + m3)

17. A lamp of mass m is suspended from two cables of unequal

length as shown to the right. Which of the following is true

about the tensions T1 and T2 in the cables?

(A) Tl > T2

(B) T1 = T2

(C) T2 > T1

(D) Tl - T2 = mg

(E) Tl + T2 = mg

18. A ball of mass m is suspended from two massless strings of an

equal length as shown below. The tension force in each string is:

(A) ½ mgcos

(B) 2mgcos

(C) mgcos

(D) mg/(cos)

(E) mg/(2cos)

19. A ball moves horizontally with an initial velocity vo, as shown above. It is then struck by a

tennis racket. After leaving the racket, the ball moves with a velocity v. Which of the

following vectors best represents the direction of the average force that the racket

exerts on the ball?

(A) (B) (C) (D) (E)

20. A marble of mass m moves along a path with a speed defined by the function v = bt2 + c,

where t is time and b and c are constants. What is the magnitude F of the net force on

the particle at time t = t1?

(A) bt1 2 + c (B) 3mbt1 + 2c (C) mbt1 (D) mbt1 + c (E) 2mbt1

21. The position as a function of time of a moving object is given by the formula

x = 2t3 – 3t2 + 4t. At what time the net force on the object is zero?

(A) 0.5 s (B) 1.0 s (C) 1.5 s (D) 1.8 s (E) 2.2 s

22. The velocity as a function of time of a moving object is shown by the graph. Which of

the following graphs best represents the magnitude of the net force exerted on the

object as a function of time?

(A) (B)

(B) (D)

(E)

23. A box of 50 kg is pulled up from rest by a cable. The tension force in the cable is 600 N.

What is the box’s velocity after it covers vertical distance of 16 m?

(A) 4 m/s (B) 8 m/s (C) 12 m/s (D) 16 m/s (E) 20 m/s

24. An Atwood machine is presented by the diagram. What is the magnitude of the

acceleration of 0.5 kg block?

(A) 6 m/s2 (B) 4 m/s2 (C) 2 m/s2 (D) 1 m/s2 (E) 0.5 m/s2

25. A 12 kg sphere is supported by two ropes AB and BC. What is the tension force in rope

BC?

(A) 120 N (B) 160 N (C) 180 N (D) 200 N (E) 240 N

26. A 12 kg sphere is supported by two ropes AB and BC. What is the tension force in rope

AB?

(A) 120 N (B) 160 N (C) 180 N (D) 200 N (E) 240 N

27. A small sphere is attached to a light string that can move in a vertical circle. The sphere

is released from point 1 and describes a semicircle when it reaches point 2. What are

the directions of the acceleration vector at point 1 and point 2?

Point 1 Point 2

(A) Downward Upward

(B) Downward To the right

(C) Upward Upward

(D) To the right Upward

(E) To the right Downward

28. A particle moves along a curved path from point 1 to point 2. Which of the following

diagrams indicates a possible combination of the net force, acceleration and velocity of

the particle?

(A) (B) (C)

(D) (E)

29. A 12 kg block is suspended from two light, identical springs. When the block is in

equilibrium the springs stretch by 30 cm. What is the spring constant of each spring?

(A) 50 N/m (B) 100 N/m (C) 120 N/m (D) 160 N/m (E) 200 N/m

30. What minimum force is required to move 10 kg block up the inclined plane with an

angle of 37 ° above the horizontal? The coefficient of kinetic friction between the block

and the inclined surface is 0.2.

(A) 76 N (B) 54 N (C) 42 N (D) 36 N (E) 28 N

31. A sphere of mass m falls in the presence of air resistance. If the air resistance force is

given F = -bv and at time t = 0 vo = 0, which of the following expressions is the velocity of

the sphere as a function of time?

(A) V = 𝑚𝑔

𝑏(1 - 𝑒−

𝑏

𝑚𝑡) (B) V =

𝑚

𝑏(1 - 𝑒−

𝑏

𝑚𝑡) (C) V =

𝑔

𝑏(1 - 𝑒−

𝑏

𝑚𝑡)

(D) V = 𝑏

𝑚𝑔(1 - 𝑒−

𝑏

𝑚𝑡) (E) V =

𝑚𝑔

𝑏(1 - 𝑒−

𝑚

𝑏𝑡)

32. In the physics lab, a student performs an experiment with a double-sided spring gun.

When the spring is compressed and then released it can fire two rubber balls m1 and m2

at the same time. From this experiment the student was able to measure only the

acceleration of each ball a1 and a2. Based on this information, which of the following can

be determined?

(A) m1 and m2 only (B) Spring force F only (C) Spring Force F, m1 and m2

(D) Ratio of m1 and m2 only (E) Ratio of m1 and m2, and spring force F only

33. A block of mass m moves with acceleration, a, down a frictionless inclined plane that

makes an angle Ɵ with the horizontal. Which of the following expressions about the

normal force on the block is correct?

(A) Fn = mg (B) Fn = mg sinƟ (C) Fn = mg cosƟ

(D) Fn = ma (E) Fn = mg tanƟ

34. A block of mass m moves with acceleration, a, down a frictionless inclined plane that

makes an angle Ɵ with the horizontal. Which of the following expressions about the

acceleration of the block is correct?

(A) a = g (B) a = g sinƟ (C) a = g cosƟ

(D) a = 2g (E) a = g tanƟ

35. A block slides at a constant velocity down the inclined plane that makes an angle Ɵ with

the horizontal. Which of the following expressions represents the coefficient of kinetic

friction between the block and the inclined surface?

(A) tanƟ (B) sinƟ (C) cosƟ (D) 1

𝑡𝑎𝑛Ɵ (E)

1

𝑠𝑖𝑛Ɵ

36. An object of mass 1 kg starts from rest and moves along a straight line. The velocity as a

function of time is given v = 3t2 + 2t. What is the instantaneous force on the object at

time t = 3 s?

(A) 10 N (B) 20 N (C) 30 N (D) 40 N (E) 50 N

37. A 10 kg box is pushed with an initial velocity of 4 m/s on a horizontal surface. The box

moves 8 m before it comes to a complete stop. What is the coefficient of kinetic friction

between the box and the surface?

(A) 0.30 (B) 0.20 (C) 0.10 (D) 0.05 (E) 0.02

38. A 10 kg block is place on top of the 20 kg block as shown. The system of two blocks can

move on a horizontal frictionless surface. The coefficient of static friction between the

blocks is 0.6. If a horizontal 150 N force is applied to the 20 kg block and the top block

doesn’t slide on the bottom block, what is the acceleration of the system?

(A) 1 m/s2 (B) 3 m/s2 (C) 5 m/s2 (D) 7 m/s2 (E) 9 m/s2

39. A 10 kg block is place on top of the 20 kg block as shown. The system of two block can

move on a horizontal frictionless surface. The coefficient of static friction between the

blocks is 0.6. If a horizontal 150 N force is applied to the 20 kg block and the top block

doesn’t slide on the bottom block, what is the magnitude of the horizontal force that

the 10 kg block exerts on the 20 kg block?

(A) 10 N (B) 20 N (C) 30 N (D) 50 N (E) 60 N

40. A block is given an initial velocity vo when it is at the bottom of a rough inclined plane.

Which of the following is true about the block as it moves?

(A) It has the same acceleration as it moves up and down the plane.

(B) It has greater acceleration as it moves up the plane and less acceleration as it

moves down the plane.

(C) It has greater acceleration as it moves down the plane and less acceleration as it

moves up the plane.

(D) It has a varying acceleration as it moves up and down the plane.

(E) It has a constant velocity as it moves up and down the plane.

Answer Key

1.C 6.C 11.A 16.C 21.A 26.B 31.A 36.B

2.C 7.B 12.D 17.C 22.E 27.A 32.D 37.C

3.C 8.A 13.B 18.E 23.B 28.E 33.C 38.C

4.D 9.C 14.B 19.D 24.C 29.E 34.B 39.D

5.D 10.C 15.A 20.E 25.D 30.A 35.A 40.B