Momentum and Energy

The unit of work is the watt. meter. joule. newton. second.

joule

Which of the following energy forms is associated with an object in motion? potential energy elastic potential energy nonmechanical energy kinetic energy

kinetic energy

The main difference between kinetic energy and potential energy is that kinetic energy involves position, and potential energy involves motion. kinetic energy involves motion, and potential energy involves position. although both energies involve motion, only kinetic energy involves position. although both energies involve position, only potential energy involves motion.

kinetic energy involves motion, and potential energy involves position.

A ball is thrown into the air with 100 J of kinetic energy, which is transformed to gravitational potential energy at the top of its trajectory. When it returns to its original level after encountering air resistance, its kinetic energy is 100 J. more than 100 J. less than 100 J. Not enough information given.

less than 100 J

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

the same

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

the same

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 less than 2 units. 2 units. more than 2 units. There is not enough information to say.

2 units

A ball with a momentum of 4.0 kg·m/s hits a wall and bounces straight back without losing any kinetic energy. What is the change in the ball's momentum? -8.0 kg·m/s -4.0 kg·m/s 0.0 kg·m/s 8.0 kg·m/s

-8.0 kg·m/s

A child moving at constant velocity carries a 2 N ice-cream cone 1 m across a level surface. What is the net work done on the ice-cream cone? 0 J 0.5 J 2 J 20 J

0 J

A worker does 25 J of work lifting a bucket, then sets the bucket back down in the same place. What is the total net work done on the bucket? -25 J 0 J 25 J 50 J

0 J

How much work is done on a 60-N box of books that you carry horizontally across a 6-m room? 0 J 6 J 10 J 60 J 360 J

0 J

What is the kinetic energy of a 0.135 kg baseball thrown at 40.0 m/s? 54.0 J 87.0 J 108 J 216 J

108 J

Suppose a moving car has 3000 J of kinetic energy. If the car's speed doubles, how much kinetic energy will it then have? 1000 J 1500 J 3000 J 6000 J 12,000 J

12,000 j

A 0.2 kg baseball is 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 momentum? 2 kg·m/s 4 kg·m/s 8 kg·m/s 20 kg·m/s

20 kg·m/s

Ball A has triple the mass and speed of ball B. What is the ratio of the kinetic energy of ball A to ball B. 3 6 9 27

27

A 3.00 kg toy falls from a height of 1.00 m. What will the kinetic energy of the toy be just before the toy hits the ground? (Assume no air resistance and that g = 9.81 m/s^2.)(mgh) 0.98 J 9.8 J 29.4 J 294 J

29.4 J

A 60-N object moves at 1 m/s. Its kinetic energy is 1 J. 3 J. 60 J. more than 60 J.

3 J

If the displacement of a horizontal mass-spring system was doubled, the elastic potential energy in the system would change by a factor of 1/4. 1/2. 2. 4.

4

A child pulls a balloon for 12 m with a force of 1.0 N at an angle 60° below horizontal. How much work does the child do on the balloon? -10 J -6.0 J 6.0 J 12 J

6.0 J

An arrow in a bow has 70 J of potential energy. Assuming no loss of energy to heat, how much kinetic energy will it have after it has been shot? 0 J 35 J 50 J 70 J 140 J

70J

How many joules of work are done on a box when a force of 25 N pushes it 3 m? 1 J 3 J 8 J 25 J 75 J

75 J

How much power is required to do 40 J of work on an object in 5 seconds? 0 W 5 W 8 W 40 W 200 W

8w

Which of the following situations is an example of a visible change in momentum? A hiker walks through a spider's web. A car drives over a pebble. A volleyball hits a mosquito in the air. A baseball is hit by a bat.

A baseball is hit by a bat.

If a force is exerted on an object, which statement is true? A large force always produces a large change in the object's momentum. A large force produces a large change in the object's momentum only if the force is applied over a very short time interval. A small force applied over a long time interval can produce a large change in the object's momentum. A small force always produces a large change in the object's momentum.

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

Which requires more work: lifting a 70-kg sack vertically 2 meters or lifting a 35-kg sack vertically 4 meters? Lifting the 70 kg sack Lifting the 35 kg sack Both require the same amount of work.

Both require the same amount of work.

What are the SI units for momentum? N·m J kg·m/s kg·m/s^2

Correct Answer

In which of the following sentences is work used in the scientific sense of the word? Holding a heavy box requires a lot of work. A scientist works on an experiment in the laboratory. Sam and Rachel pushed hard, but they could do no work on the car. John learned that shoveling snow is hard work.

Sam and Rachel pushed hard, but they could do no work on the car.

In which of the following sentences is work used in the everyday sense of the word? Lifting a heavy bucket involves doing work on the bucket. The force of friction usually does negative work. Sam and Rachel worked hard pushing the car. Work is a physical quantity.

Sam and Rachel worked hard pushing the car

If friction is the only force acting on an object during a given physical process, which of the following assumptions can be made in regard to the object's kinetic energy? The kinetic energy decreases. The kinetic energy increases. The kinetic energy remains constant. The kinetic energy decreases and then increases.

The kinetic energy decreases

Which has more momentum, a large truck moving at 30 miles per hour or a small truck moving at 30 miles per hour? Both have the same momentum. The small truck The large truck

The large truck

When comparing the momentum of two moving objects, which of the following is correct? The object with the higher velocity will have less momentum if the masses are equal. The more massive object will have less momentum if its velocity is greater. The less massive object will have less momentum if the velocities are the same. The more massive object will have less momentum if the velocities are the same.

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

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. all of the above

all of the above

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. all of the above none of the above

all of the above

In order to increase the final momentum of a golf ball, we could increase the force acting on it. follow through when hitting the ball. increase the time of contact with the ball. swing as hard as possible. all of the above

all of the above

Energy is changed from one form to another with no net loss or gain. Sometimes true Always false Always true

always true

A cannon recoils from launching a cannonball. The speed of the cannon's recoil is small because the impulse on the cannon is less than the impulse on the cannonball. cannon has far more mass than the cannonball. momentum of the cannon is unchanged. force against the cannon is relatively small. none of the above

cannon has far more mass than the cannonball.

Which of the following energy forms is not involved in hitting a tennis ball? kinetic energy chemical potential energy gravitational potential energy elastic potential energy

chemical potential energy

A 20 kg shopping cart moving at a velocity of 0.5 m/s collides with a store wall and stops. The momentum of the shopping cart increases. decreases. remains the same. is conserved.

decreases

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

doubled

Two billiard balls collide. Identify the type of collision. elastic nearly elastic inelastic perfectly inelastic

elastic

In physics, work is defined as force times time. force divided by distance. distance divided by time. force divided by time. force times distance.

force times distance

How much farther will a car traveling at 100 km/s skid than the same car traveling at 50 km/s? Half as far. The same distance. Twice as far. Four times as far. Five times as far.

four times as far

If Nellie Newton pushes an object with twice the force for twice the distance, she does twice the work. the same work. four times the work. eight times the work.

four times the work.

Consider molecules of hydrogen gas and molecules of heavier oxygen gas that have the same kinetic energy. The molecules with the greater speed are hydrogen. Both have the same speed. oxygen.

hydrogen

The reason padded dashboards are used in cars is that they look nice and feel good. decrease the impulse in a collision. increase the force of impact in a collision. decrease the momentum of a collision. increase the time of impact in a collision.

increase the time of impact in a collision.

When a car's speed triples, its kinetic energy remains the same. triples. increases by four times. increases by nine times. none of the above

increases 9 times

After colliding, objects are deformed and lose some kinetic energy. Identify the type of collision. elastic nearly elastic inelastic perfectly inelastic

inelastic

The impulse experienced by a body is equivalent to the body's change in velocity. kinetic energy. momentum. force.

momentum

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 acceleration. momentum. speed. all of the above none of the above

momentum

In a two-body collision, momentum is always conserved. kinetic energy is always conserved. neither momentum nor kinetic energy is conserved. both momentum and kinetic energy are always conserved.

momentum is always conserved.

An object that has kinetic energy must be at rest. falling. moving. elevated.

moving

A heavy object and a light object are released from rest at the same height and time in a vacuum. As they fall, they have equal energies. weights. momenta. all of the above none of the above

none of the above

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 zero. one half as large. the same. twice as large. More information is needed to say.

one half as large

Two objects stick together and move with a common velocity after colliding. Identify the type of collision. elastic nearly elastic inelastic perfectly inelastic

perfectly inelastic

Which of the following energy forms is associated with an object due to its position? potential energy positional energy total energy kinetic energy

potential energy

A job is done slowly, and an identical job is done quickly. Both jobs require the same amount of work but different amounts of energy. power. both A and B none of the above

power

A soccer ball collides with another soccer ball at rest. The total momentum of the ball is zero. increases. remains constant. decreases.

remains constant

Which has greater kinetic energy, a car traveling at 30 km/h or a half-as-massive car traveling at 60 km/h? The 60 km/h car Both have the same kinetic energy. The 30 km/h car

the 60km/h car

Suppose an astronaut in outer space wishes to toss a ball against a very massive and perfectly elastic concrete wall and catch it as it bounces back. If the ball is as massive as the astronaut, then the astronaut's time between catches will decrease as the game progresses. the astronaut will never catch the first bounce. the astronaut will catch one bounce only. none of the above

the astronaut will never catch the first bounce.

If the sign of work is negative, the displacement is perpendicular to the force. the displacement is in the direction opposite the force. the displacement is in the same direction as the force. no work is done.

the displacement is in the direction opposite the force.

The change in an object's momentum is equal to the product of the mass of the object and the time interval. the product of the force applied to the object and the time interval. the time interval divided by the net external force. the net external force divided by the time interval.

the product of the force applied to the object and the time interval.

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 decreased. the time of impact is increased. the velocity of the hand is reduced. the momentum of impact is reduced. none of the above

the time of impact is increased.

The law of conservation of momentum states that the total initial momentum of all objects interacting with one another usually equals the total final momentum. the total initial momentum of all objects interacting with one another does not equal the total final momentum. the total momentum of all objects interacting with one another is zero. the total momentum of all objects interacting with one another remains constant regardless of the nature of the forces between the objects.

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

The amount of potential energy possessed by an elevated object is equal to the power used to lift it. the distance it is lifted. the force needed to lift it. the work done in lifting it. the value of the acceleration due to gravity.

the work done in lifting it.

Two skaters stand facing each other. One skater's mass is 60 kg, and the other's mass is 72 kg. If the skaters push away from each other without spinning, the lighter skater has less momentum. their momenta are equal but opposite. their total momentum doubles. their total momentum decreases.

their momenta are equal but opposite.

Momentum of a system is conserved only when there are no internal forces acting on the system. the system is not moving. there is no net external force acting on the system. the system has zero momentum.

there is no net external force acting on the system

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 bend over touching the ice in front of her and then bring her feet to her hands. walk very slowly on tiptoe. get on her hands and knees and crawl off the ice. throw something in the direction opposite to the way she wants to go. all of the above will work

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

Compared to a sports car moving at 30 miles per hour, the same sports car moving at 60 per hour has twice as much momentum. four times as much momentum. the same momentum.

twice as much momentum

A person sitting in a chair with wheels stands up, causing the chair to roll backward across the floor. The momentum of the chair was zero while stationary and increased when the person stood. was greatest while the person sat in the chair. remained the same. was zero when the person got out of the chair and increased while the person sat.

was zero while stationary and increased when the person stood.

The unit of power is the newton. meter. joule. second. watt.

watt

Power is defined as the force on an object divided by the time the force acts. work done times the time taken to do that work. work done on an object divided by the time taken to do the work. distance divided by the time taken to move that distance. force on an object times the distance the object moves.

work done on an object divided by the time taken to do the work.

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 small but noticeable. the same as before. zero.

zero