Ch. 6 Practice Questions

impulses are normally smaller when bouncing takes place

False

momentum is a scalar quantity

False

automobile dashboards that are padded lengthen the time of impact in case of a collision

True

if a net force acts on a system, the system's momentum will change

True

impulse is defined as the force exerted on an object times the time it lasts

True

when a baseball player follows through in hitting the ball, the contact time with the ball is longer

True

when two objects collide and completely bounce apart with no lasting deformation or generation of heat, the collision is said to be elastic

True

A freight train rolls along a track with considerable momentum. If it were to roll at the same speed but has twice as much mass, its momentum would be

doubled

In order to catch a ball, a baseball player moves his or her hand backward in the direction of the ball's motion. Doing this reduces the force of impact on the player's hand principally because

the time of impact is increased

Which has more momentum, a large truck moving at 30 miles per hour or a small truck moving at 30 miles per hour?

the large truck

A table tennis ball launcher is fired. Compared to the force on the ball, the force on the launcher is

the same

A table tennis ball launcher is fired. Compared to the impulse on the ball, the impulse on the launcher is

the same

Recoil is noticeable if you throw a heavy ball while standing on roller skates. If instead you go through the motions of throwing the ball but hold onto it, your net recoil velocity will be:

0

a piece of putty moving with 2 units of momentum strikes and sticks to a heavy bowling ball that is initially at rest. After the putty sticks to the ball, both are set in motion with a combined momentum that is:

2 units

a ball is moving at 6.0 m/s and has a momentum of 24.0 kg x m/s. what is the balls mass?

4.0 kg

a 4.0 kg ball has momentum of 20.0 kg x m/s. what is the balls speed?

5.0 m/s

a 2 Kg ball is thrown at 3m/s. what is the balls momentum?

6 kg x m/s

a cannonball shot from a long-barrel cannon travels faster than one shot from a short-barrel cannon because the cannon receives a greater

Impulse

a meteor that originally was headed south breaks up into two chunks. One of the chunks moves southwest, the second chunk was not immediately found, but scientists guesses that they should look for an object heading

Southeast

the force that accelerates a rocket into outer space is exerted on the rocket by

The exhaust gases

a piece of putty and a rubber ball have the same mass. If you drop them from the same height, which object will produce a greater impulse and why?

The rubber ball will produce a greater impulse because it will bounce when it hits the ground

The momentum change of an object is equal to the

impulse acting on it

If the momentum of an object changes and its mass remains constant

it is accelerating (or decelerating). , there is a force acting on it, its velocity is changing.

A car traveling along the highway needs a certain amount of force exerted on it to stop. More stopping force may be required when the car has

less stopping distance, more momentum, more mass

The momentum of an object is defined as the object's

mass times its velocity

Two objects, A and B have the same size and shape, but A is twice as heavy as B. When they are dropped simultaneously from a tower, they reach the ground at the same time, but A has a higher

momentum

When you jump off a step, you usually bend your knees as you reach the ground. By doing this, the time of the impact is about 10 times more what it would be in a stiff-legged landing, and the average force on your body is reduced by

more than 10 times

A moving freight car runs into an identical car at rest on the track. The cars couple together. Compared to the velocity of the first car before the collision, the velocity of the combined cars after the collision is:

one half as large

Suppose a girl is standing on a pond where there is no friction between her feet and the ice. In order to get off the ice she can

throw something in the direction opposite to the way she wants to go.

while roller-skating, granny collides with her tiny grandson Ambrose who is at rest. Ignoring any friction effects, Ambrose's speed after the collision will be greatest when

He and granny make a bouncing collision, each going in opposite directions

superman is at rest when he throws an asteroid that has more mass than he does. Which moves faster, superman or the asteroid?

Superman

Which of the following has the largest momentum?

a pickup truck traveling down the highway (compared to a truck parked in the parking lot, a tightrope walker across the Niagara Falls, Schott Hall, a dog running down the street)

A collision is considered elastic if

there is no lasting deformation, the objects don't stick together, the objects that collide don't get warmer, after the collision, the objects have the same shape as before the collision.

Momentum of a system is conserved only when

there is no net external force acting on the system

Compared to a sports car moving at 30 miles per hour, the same sports car moving at 60 miles per hour has

twice as much momentum