AP Physics C Classroom Momentum Review

Thin rods A, B, and C all have uniform mass distibution and are all of equal length L. The center of mass of the three-rod system is shown above. If both A and C have a mass M, the ratio of the mass of bar B to the mass of bar A,  $\frac{m_B}{m_A}$  , is

• 1/1

• 2/1

• 4/1

• 6/1

• 8/1

A ball is traveling through the air as represented by the initial momentum vector shown above on the left. A racket then makes contact with the ball, as shown in the middle figure above. After the racket makes contact with the ball, the ball is traveling through the air as represented by the momentum vector shown above on the right. Which of the following vectors could represent the impulse the racket exerts on the ball?

• A vector that points in the rightward direction

• A vector that points up and to the right

• A vector that points straight up

• A vector that points straight down

• A vector that points straight to the left

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-2

NGSS.HS-PS2-3

A stationary golf ball is hit by a club. While the club is in contact with the ball, the ball compresses, the club exerts maximum force when the ball is at maximum compression, and then the ball expands. The momentum of the golf ball after contact with the club is represented by the vector above. Which of the following groups of vectors could represent the force exerted on the ball at the three moments described?

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Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-2

Students perform an experiment with the goal of finding the relationship between the force applied to an object and the time required to stop the object. During the experiment, a student jumps and lands on a large sensor that measures the magnitude of the force exerted on the scale and the time it takes to bring the student to rest. During the first trial, the student jumps and lands on the sensor while keeping their legs perfect straight. Which of the following describes a proper change in procedure to correctly find the relationship between the force applied to an object and the time required to stop the object?

• Jump to the same height and land with knees bent. This will increase the time to bring the student to rest and decrease the magnitude of the force.

• Jump to the same height and land with knees bent. This will decrease the time to bring the student to rest and increase the magnitude of the force.

• Jump higher and land with knees bent. This will increase the time to bring the student to rest and decrease the magnitude of the force.

• Jump higher and land with knees bent. This will decrease the time to bring the student to rest and increase the magnitude of the force.

• Jump higher and land with legs straight. This will increase the time to bring the student to rest and decrease the magnitude of the force.

An object of mass  $M$   is at rest at the origin at time  $t=0$  . At that time, a force  $F=At^2$  (where  $A$  is a positive constant and  $F$  is in newtons when  $t$  is in seconds) is applied to the object. After 2 s, the velocity of the object in m/s will be

•  $\frac{2A}{M}$  

•  $\frac{3A}{M}$  

•  $\frac{4A}{M}$  

•  $\frac{8A}{M}$  

•  $\frac{8A}{3M}$  

Tags

NGSS.HS-PS2-1

A 2.0 kg ball is dropped from a height of 20 m onto a soft surface and rebounds to a height of 5.0 m. What is the magnitude of the impulse exerted on the ball by the floor?

• 10 N·s

• 20 N·s

• 40 N·s

• 60 N·s

• 100 N·s

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-2

Two blocks are sliding toward one another along a level horizontal surface. One block is moving due east, and the other block is moving due west. The two blocks collide. Which of the following is NOT a possible set of directions the two blocks could be traveling after the collision?

• Both blocks are traveling east after the collision.

• Both blocks are traveling west after the collision.

• One block travels northeast, and the other block travels northwest.

• One block travels southwest, and the other block travels northeast.

• One block travels southeast, and the other block travels northwest.

Tags

NGSS.HS-PS2-2

In an experiment, a student places two carts on a level horizontal track with photogates X and Y that help the student determine the speeds of the carts, as shown above. The carts move toward each other with negligible friction. Cart A of mass  $m_A$  is moving to the right with speed  $v_A$  . Cart B of mass  $m_B\left(m_B>2m_A\right)$  is moving to the left with speed  $v_B\left(v_B>3v_A\right)$  . After passing through the photogates, the two carts collide. After the collision, cart  A bounces back to the left at speed  $v_{Af}\left(v_{Af}<v_B\right)$  . Which of the following gives the correct speed and direction of motion for cart  after the collision?

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Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-2

In an experiment, a student places two carts on a level horizontal track with photogates X and Y that help the student determine the speeds of the carts, as shown above. The carts move toward each other with negligible friction. Cart A of mass  $m_A$  is moving to the right with speed  $v_A$  . Cart B of mass  $m_B\left(m_B>2m_A\right)$  is moving to the left with speed  $v_B\left(v_B>3v_A\right)$  . After passing through the photogates, the two carts collide. In a new experiment, a spring is attached to the right end of cart A. Cart  B is at rest between the photogates when cart  A is given an initial speed to the right, passes through photogate X, and collides with cart B. The speed of each cart before and after the collision is measured. It is discovered that the sum of the kinetic energies of the two carts after the collision is about 5% greater than the kinetic energy of cart A before the collision. Which of the following is the best explanation for the difference in the kinetic energy?

• The scale used to determine the masses of the carts is off by 5%.

• During the collision, some of the kinetic energy of the carts is converted to heat.

• Some of the elastic potential energy of the spring is converted to kinetic energy.

• There is a small amount of friction between the track and the carts.

• One end of the track is slightly higher than the other.

Tags

NGSS.HS-PS2-2

In an experiment, a student places two carts on a level horizontal track with photogates X and Y that help the student determine the speeds of the carts, as shown above. The carts move toward each other with negligible friction. Cart A of mass  $m_A$  is moving to the right with speed  $v_A$  . Cart B of mass  $m_B\left(m_B>2m_A\right)$  is moving to the left with speed  $v_B\left(v_B>3v_A\right)$  . After passing through the photogates, the two carts collide.  In addition to the initial speeds and masses of the carts, increasing the precision of which of the following measurements would decrease the error when determining if the collision between the two carts is elastic?

I: The length of each cart

II: The distance between the photogates

III: The time it takes each cart to reach a photogate after the collision

IV: The time it takes each cart to move through a photogate after the collision

• I and III only
  

• II and III only
  

• I and IV only
  

• II and IV only
  

• II, III and IV
  

Tags

NGSS.HS-PS2-2