Chapter 6

A ball with a mass of 0.15 kg and a veloci ty of 5.0 m/ s strikes a wall and bounces straight b ack with a velocity of 3.0 m/ s. What is the change in momentum of the ball?

-1.20 kg •m/ s

A 6.0 × 10 -2 kg tennis ball moves at a velocity of 12 m/ s. The ball is struck by a racket, causing it to rebound in the opposite direction at a speed of 18 m/ s. Wha t is the change in the ball's momentum?

-1.8 kg •m/ s

A rubber ball with a mass of 0.30 kg is dr opped onto a steel plate. The ball's velocity just before impact is 4.5 m/ s and just after impact is 4.2 m/ s. What is t he change in the ball's momentum?

-2.6 kg •m/ s

A softball with a mass of 0.11 kg moves at a speed of 12 m/ s. Then the ball is hit by a bat a nd rebounds in the opposite direction at a speed of 15 m/ s. What is th e change in momentum of the ball?

-3.0 kg •m/ s

A ball with a momentum of 4.0 kg •m/ s hits a wall and bounces straight back without l osing any kinetic energy. What is the change in the ball's momentum?

-8.0 kg •m/ s

Two skaters, each with a mass of 50 kg, ar e stationary on a frictionless ice pond. One skater throws a 0.2 kg ball at 5 m/ s to the other skater, who catches it. What are the velocities of the skaters when the bal l is caught?

0.02 m/ s moving apart

A 65.0 kg ice skater standing on frictionl ess ice throws a 0.15 kg snowball horizontally at a speed of 32.0 m/ s. At what velocity does the skater move backward ?

0.07 m/ s

An object with a mass of 0.10 kg makes an elastic head-on collision with a stationary object with a mass of 0.15 kg. The final velocity of the 0.10 kg object a fter the collision is -0.045 m/ s and the final velo city of the 0.15 kg object after the collision is 0.16 m/ s. Wha t was the initial velocity of the 0.10 kg object?

0.20 m/ s

An astronaut with a mass of 70.0 kg is out side a space capsule when the tether line breaks. T o return to the capsule, the astronaut throws a 2.0 kg wrench away from the capsule at a speed of 14 m/ s. At what spee d does the astronaut move toward the capsule?

0.4 m/ s

A swimmer with a mass of 75 kg dives off a raft with a mass of 500 kg. If the swimmer's speed is 4 m/ s immediately after leaving the raft, what is the spe ed of the raft?

0.6 m/ s

An infant throws 5 g of applesauce at a ve locity of 0.2 m/ s. All of the applesauce collides with a nearby wall and sticks. What is the decrease in kinetic energy of the applesauce?

1 × 10 -4 J

A diver with a mass of 80.0 kg jumps from a dock into a 130.0 kg boat at rest on the west sid e of the dock. If the velocity of the diver in the air is 4.10 m/ s to the west, what is the final velocity of the diver after landing in the boat?

1.56 m/ s to the west

A 90 kg halfback runs north and is tackled by a 120 kg opponent running south at 4 m/ s. The c ollision is perfectly inelastic. Just after the tackle, both pl ayers move at a velocity of 2 m/ s north. Calculate the velocity of the 90 kg player just before the tackle.

10 m/ s north

Each croquet ball in a set has a mass of 0 .50 kg. The green ball travels at 10.5 m/ s and stri kes a stationary red ball. If the green ball stops moving, what is the f inal speed of the red ball after the collision?

10.5 m/ s

Two snowballs with masses of 0.40 kg and 0 .60 kg, respectively, collide head-on and combine t o form a single snowball. The initial speed for each is 15 m/ s. If the velocity of the snowball with a mass of 1.0 kg is 3.0 m/ s after the collision, what is the decrease i n kinetic energy?

110 J

Two carts with masses of 1.5 kg and 0.7 kg, respectively, are held together by a compressed s pring. When released, the 1.5 kg cart moves to the left with a velocity of 7 m/ s. What is the velocity of the 0.7 kg cart? (Disregard the mass of the spring.)

15 m/ s to the right

A 0.2 baseball if pitched with a velocity of 40 m/ s and is then batted to the pitcher with a velocity of 60 m/ s. What is the magnitude of change in the ball's momen tum?

20 kg •m/ s

A bullet with a mass of 5.00 × 10 -3 kg is loaded into a gun. The loaded gun has a mass of 0.52 kg. The bullet is fired, causing the empty gun to recoil at a spee d of 2.1 m/ s. What is the speed of the bullet?

220 m/ s

A clay ball with a mass of 0.35 kg strikes another 0.35 kg clay ball at rest, and the two bal ls stick together. The final velocity of the balls is 2.1 m/ s north. W hat was the first ball's initial velocity?

3 m/ s to the right

What velocity must a 1340 kg car have in order to have the same momentum as a 2680 kg truck tr aveling at a velocity of 15 m/ s to the west?

3.0 × 10 1 m/ s to the west

A clay ball with a mass of 0.35 kg has an initial speed of 4.2 m/ s. It strikes a 3.5 kg clay ball at rest, and the two balls stick together and remain stationary. Wha t is the decrease in kinetic energy of the 0.35 kg ball?

3.1 J

A 15 g marble moves to the right at 3.5 m/ s and makes an elastic head-on collision with a 22 g marble. The final velocity of the 15 g marble is 5.4 m/ s to the left, and the final velocity of the 22 g marble is 2.0 m/ s to the right. What is the initial velocity of the 22 g marble?

4.0 m/ s to the left

A clay ball with a mass of 0.35 kg strikes another 0.35 kg clay ball at rest, and the two bal ls stick together. The final velocity of the balls is 2.1 m/ s north. W hat was the first ball's initial velocity?

4.2 m/ s to the north

A bowling ball with a mass of 7.0 kg strikes a pin that has a mass of 2.0 kg. The pin flies f orward with a velocity of 6.0 m/ s, and the ball continues forward at 4.0 m/ s. What was the original velocity of the ball?

5.7 m/ s

A 1.5 × 10 3 kg truck moving at 15 m/ s strikes a 7.5 × 10 2 kg automobile stopped at a traffic light. The vehicles hook bumpers and skid together at 10.0 m/ s. What is the decrease in kinetic energy?

6.0 × 10 4 J

Which of the following situations is an ex ample of a visible change in momentum?

A baseball is hit by a bat.

Which of the following statements properly relates the variables in the equation F∆t = ∆p?

A large constant force acting over a long time in terval causes a large change in momentum.

If a force is exerted on an object, which statement is true?

A small force applied over a long time interval c an produce a large change in the object's momentum.

Which of the following situations is an ex ample of change in momentum?

A tennis ball is hit into a net.

A billiard ball collides with a stationary identical billiard ball in an elastic head-on coll ision. After the collision, which is true of the first ball?

It comes to r est.

Which of the following statements about th e conservation of momentum is NOT correct?

Momentum is not conserved for a system of objects in a head-on collision.

A child with a mass of 23 kg rides a bike with a mass of 5.5 kg at a velocity of 4.5 m/ s to th e south. Compare the momentum of the child with the momentum of the bike.

The child has a greater momentum than the bike.

A baseball is pitched very fast. Another ba seball of equal mass is pitched very slowly. Which of the following statements is correct?

The fast-moving baseball is harder to stop becaus e it has more momentum.

When comparing the momentum of two moving o bjects, which of the following is correct?

The less massive object will have less momentum i f the velocities are the same.

Which of the following has the greatest momentum?

car with a mass of 1210 kg moving at a velocity o f 51 m/ s

A 75 kg person walking around a corner bumped into an 80 kg person who was running around the same corner. The momentum of the 80 kg person

decreased.

A 20 kg shopping cart moving at a velocity of 0.5 m/ s collides into a store wall and stops. T he momentum of the shopping cart

decreases.

Two billiard balls collide. Identify the t ype of collision.

elastic

Two objects move separately after collidin g, and both the total momentum and total kinetic en ergy remain constant. Identify the type of collision.

elastic

An ice skater initially skating at a veloc ity of 3 m/ s speeds up to a velocity of 5 m/ s. The momentum of the skater

increases.

After colliding, objects are deformed and lose some kinetic energy. Identify the type of coll ision.

inelastic

A roller coaster climbs up a hill at 4 m/ s and then zips down the hill at 30 m/ s. The momentum of the roller coaster

is greater down the hill than up the hill.

Paint is splattered on a canvas. After the paint sticks to the canvas, the total momentum of the paint and canvas

is zero.

Which of the following best describes the kinetic energy of each object after a two-body coll ision if the momentum of the system is conserved?

might also be conserved

In a two-body collision,

momentum is conserved.

The impulse experienced by a body is equivalent to the body's change in

momentum.

Which of the following best describes the momenta of two bodies after a two-body collision if the kinetic energy of the system is conserved?

must also be conserved

A large moving ball collides with a small stationary ball. The momentum

of the large ball decreases, and the momentum of the small ball increases.

Two balls of dough collide and stick toget her. Identify the type of collision.

perfectly inelastic

Two objects stick together and move with t he same velocity after colliding. Identify the type of collision.

perfectly inelastic

A rubber ball moving at a speed of 5 m/ s h it a flat wall and returned to the thrower at 5 m/ s. The magnitude of the momentum of the rubber ball

remained the same.

A soccer ball collides with another soccer ball at rest. The total momentum of the balls

remains constant.

A force is applied to stop a moving shoppi ng cart. Increasing the time interval over which th e force is applied

requires a smaller for ce.

Two objects with different masses collide and bounce back after an elastic collision. Before the collision, the two objects were moving at velocities equal in magn itude but opposite in direction. After the collisio n,

the less massive object had gained momentum.

In an elastic collision between two object s with unequal masses,

the momentum of one object will increase by the a mount that the momentum of the other object decreases.

The change in an object's momentum is equa l to

the product of the force applied to the object an d the time interval.

A moderate force will break an egg. Howeve r, an egg dropped on the road usually breaks, while one dropped on the grass usually does not break because for the egg dropped on the grass,

the time inte rval for stopping is greater.

The law of conservation of momentum states that

the total momentum of all objects interacting wit h one another remains constant regardless of the nature of the forces between the objects.

Two skaters stand facing each other. One s kater's mass is 60 kg, and the other's mass is 72 kg. If the skaters push away from each other without spinning,

their momenta are equal but opposite.

Two swimmers relax close together on air mattresses in a pool. One swimmer's mass is 48 kg, a nd the other's mass is 55 kg. If the swimmers push away from each other,

their momenta are equal but opposite.

Which of the following has the greatest momentum?

tortoise with a mass of 270 kg moving at a veloci ty of 0.5 m/ s

A billiard ball collides with a second ide ntical ball in an elastic head-on collision. What i s the kinetic energy of the system after the collision compared with the kinetic energy before the collision?

unchanged

A person sitting in a chair with wheels sta nds, causing the chair to roll backward across the floor. The momentum of the chair

was zero while stationary and increased when the person stood.

A student walks to class at a velocity of 3 m/ s. To avoid walking into a door as it opens, the student slows to a velocity of 0.5 m/ s. Now late for class, the stud ent runs down the corridor at a velocity of 7 m/ s. The student had the least momentum

while dodging the opening door.