Physics Chapter 7

Three objects are moving along a straight line as shown in the figure. Taking the positive direction to be to the right, what is the total momentum of this system? +106 kg • m/s -106 kg • m/s +14.0 kg • m/s -14.0 kg • m/s 0.00 kg • m/s

-14.0 kg x m/s

a 0.14-kg baseball is dropped from rest from a height of 2.0 m above the ground. What is the magnitude of its momentum just before it hits the ground if we neglect air resistance? 0.28 kg • m/s 0.88 kg • m/s 0.44 kg • m/s 0.62 kg • m/s 1.4 kg • m/s

0.88kg x m/s

A 320-g air track cart traveling at 1.25 m/s suddenly collides elastically with stationary 270 g cart. What is the speed of the 270 g cart just after the collision? 0.678 m/s 0.106 m/s 1.36 m/s 1.14 m/s 2.72 m/s

1.36 m/s

A 900 kg car traveling east at 15.0 m/s suddenly collides with 750 kg car traveling north at 20.0 m/s. The cars stick together after the collision. What is the speed of the wreckage just after the collision? 6.10 m/s 12.2 m/s 25.0 m/s 35.0 m/s 17.3 m/s

12.2 m/s

Two dogs, Rover and Fido, run on a level friction less surface. Rover runs eastward with a momentum of 24 kg x m/s and Fido runs northward with momentum 10 kg x m/s. They make a sudden perfectly inelastic collision. What is the magnitude of their combined momentum after the collision? 14 kg . m/s 26 kg . m/s 34 kg . m/s It cannot be determined without knowing the masses and velocities of the dogs.

26 kg x mg

A block of mass m = 34 kg and speed V is behind a block of mass M = 81 kg and speed of 0.50 m/s as shown in the figure. The surface is friction less and the blocks collide and couple. After the collision, the blocks have a common speed of 0.90 m/s . What is the magnitude of the impulse on the .34 kg block due to the collision? 32 N • s 14 N • s 41 N • s 57 N • s 73 N • s

32 N x s

A 0.10 kg ball, traveling horizontally at 25 m/s strikes a wall and rebounds at 19 m/s. What is the magnitude of the change in the momentum of the ball during the rebound? 1.2 kg • m/s 1.8 kg • m/s 4.4 kg • m/s 5.4 kg • m/s 72 kg • m/s

4.4 kg x m/s

Calculate the impulse due to a force of 4.5N that lasts for 1.4s 6.3 kg• m/s 5.0 kg• m/s 5.7 kg• m/s 6.9 kg• m/s

6.3 kg x m/s

A 1200 kg car moving at 15.6 m/s suddenly collides with a stationary car of mass 1500 kg. If the two vehicles lock together, what is their combined velocity immediately after the collision? 6.9 m/s 8.6 m/s 12.1 m/s 5.5 m/s

6.9 m/s

A block of mass m = 9.0 kg and speed V and is behind a block of mass M = 27 kg and speed of 0.50 m/s as shown in the figure. The surface is friction less, and the blocks suddenly collide and couple. After the collision, the blocks have a common speed of 0.90 m/s. How much kinetic energy of the blocks is lost due to collisions? 8.6 J 2.0 J 4.6 J 11 J 31 J

8.6 J

In a game of pool, the white cue ball hits the #5 ball and stops, while #5 ball moves away with the same velocity as the cue ball has originally. Both balls have the same mass. This type of collisions us (assume they have the same mass) somewhat inelastic. elastic. completely inelastic.

elastic

in an inelastic collision involving an isolated system, the final total momentum is exactly the same as the initial momentum. more than the initial momentum. less than the initial momentum.

exactly the same as the initial momentum

Impulse is change in force true false

false

In inelastic collisions energy is conserved true false

false

the momentum of an isolated system is conserved only in inelastic collisions. only in elastic collisions. in both elastic and inelastic collisions.

in both elastic and inelastic collisions

A railroad car collides with and sticks to an identical railroad car that is initially at rest. After the collision, the kinetic energy of the system is the same as before. is half as much as before. is one third as much as before. is one fourth as much as before. is one quarter as much as before.

is half as much as before

In the figure, determine the character of the collision. The masses of the blocks, and the velocities before and after, are shown. (Kinetic Energy is lost) The collision is perfectly elastic. partially inelastic. completely inelastic. characterized by an increase in kinetic energy. not possible because momentum is not conserved.

partially inelastic

Two friends are standing on opposite ends of a canoe that is initially at rest with respect to a frictionless lake. The person in the front throws a very massive ball toward the back, and the person in the back catches it. After the ball is caught, the canoe is moving backward. stationary. moving forward.

stationary

A rubber ball and a lump of clay have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same speed with which it hit. The clay sticks to the wall. Which one of these objects experiences the greater momentum change? the ball the clay Both of them experience the same non-zero momentum change. Both of them experience zero momentum change.

the ball

A very elastic rubber ball is dropped from a certain height and hits the floor with a downward speed. Since it is so elastic the ball bounces back with the same speed going upward. Which of the following statements about the bounce are correct?The ball had the same momentum just before and just after the bounce. (Direction also) The magnitude of the ball's momentum was the same just before and just after the bounce. The ball's momentum was conserved during the bounce. (When the ball has hit and stopped) None of the above statements are correct.

the magnitude of the ball's momentum was the same just before and just after the bounce.

in a collision between two unequal masses, which mass receives a greater magnitude impulse? the larger mass the smaller mass They receive equal impulses.

they receive equal impulses

In elastic collisions energy is conserved true false

true

Momentum is always conserved when objects collide true false

true