Physics

80 kg.m/s

A 10-kg bowling ball moving at 4 m/s bounces off a spring at about the same speed that it had before bouncing. What is the change in momentum of the bowling ball?

30 N

A 10-kg cement block moving horizontally at 6 m/s plows into a bank of sand and comes to a stop in 2 s. What is the average impact force on the bank?

5 m/s

A 30-kg girl and a 50-kg boy face each other on friction-free roller skates. The girl pushes the boy, who moves away at a speed of 3 m/s. What is the girl's speed?

188 W

A 30-kg girl runs up the staircase to a floor 5 m higher in 8 seconds. What is her power output?

2.9 m/s toward the right

A 40-kg football player leaps through the air to collide with and tackle a 50-kg player heading toward him, also in the air. If the 40-kg player is heading to the right at 9 m/s and the 50-kg player is heading toward the left at 2 m/s, what is the speed and direction of the tangled players?

1.3 m/s

A 5-kg blob of clay moving horizontally at 4 m/s has a head-on collision with a 4-kg blob of clay that moves toward it at 2 m/s. What is the speed of the two blobs stuck together immediately after the collision?

d. 50 kg * m/s

A 5.0-kg chunk of putty moving at 10.0 m/s collides with and sticks to a 7.0-kg bowling ball that is initially at rest. The bowling ball with its putty passenger will then be set in motion with a momentum of a. 0 kg•m/s. b. 2.0 kg•m/s. c. 15.0 kg•m/s. d. 50.0 kg•m/s. e. more than 50.0 kg•m/s.

45 km/h

A 50-kg cart moving at 100 km/h collides head-on with an approaching 50-kg cart moving at 10 km/h (in the opposite direction). If the two carts stick together, what will be their speed?

.04 m/s

A 70-kg free-floating astronaut fires 0.10-kg of gas at a speed of 30 m/s from her propulsion pistol. What is the astronaut's recoil speed?

c. less than 100 J

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 a. 100 J. b. more than 100 J. c. less than 100 J.

a. if the mass of the canonball equals the mass of the canon

A cannon fires a cannonball. The speed of the cannonball will be the same as the speed of the recoiling cannon a. if the mass of the cannonball equals the mass of the cannon. b. because momentum is conserved. c. because velocity is conserved. d. because both velocity and momentum are conserved. e. none of the above

b. impulse

A cannonball shot from a long-barrel cannon travels faster than one shot from a short-barrel cannon because the cannonball receives a greater a. force. b. impulse. c. both A and B d. neither A nor B

d. all of the above

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 a. less stopping distance. b. more momentum. c. more mass. d. all of the above e. none of the above

180 m

A car traveling at 50 km/h will skid 20 m when its brakes are locked. If the same car is traveling at 150 km/h, what will be its skidding distance?

not enough information to say

A cement truck of mass 16,000 kg moving at 15 m/s slams into a cement wall and comes to a halt. What is the force of impact on the truck?

e. all of the above

A collision is considered elastic if a. there is no lasting deformation. b. the objects don't stick together. c. the objects that collide don't get warmer. d. after the collision, the objects have the same shape as before the collision. e. all of the above

81 W

A couch potato might consume 7 million J of energy in a day. What is this rate of energy consumption in watts?

e. none of the above

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 a. energies. b. weights. c. momenta. d. all of the above e. none of the above

4.2 m/s

A loaded freight car has 5 times as much mass as an empty freight car. If the loaded car coasts at 5 m/s and collides with and attaches to the empty car at rest, what will be the speed of both cars after collision?

a. 10%

A machine puts out 100 watts of power for every 1000 watts put into it. The efficiency of the machine is a. 10%. b. 50%. c. 90%. d. 110%. e. none of the above

b. the rubber ball will produce a greater impulse because it will bounce

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? a. The silly putty will produce a greater impulse because it will bounce. b. The rubber ball will produce a greater impulse because it will bounce. c. The silly putty will produce a greater impulse because it will stop when it hits the ground. d. The rubber ball will produce a greater impulse because it will stop when it hits the ground.

b. 2 units

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 a. less than 2 units. b. 2 units. c. more than 2 units. d. There is not enough information to say.

a. limousine

A small economy car (low mass) and a limousine (high mass) are pushed from rest across a parking lot, equal distances with equal forces. The car that receives the greater impulse is the a. limousine. b. small economy car. c. neither A nor B (same for each).

b. the same

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

c. the same.

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

c. more than 5 units

A table tennis ball moving forward with 5 units of momentum strikes and bounces backward off a heavy bowling ball that is initially at rest and free to move. The bowling ball is set in motion with a momentum of a. less than 5 units. b. 5 units. c. more than 5 units. d. not enough information.

40 J

A toy cart moves with a kinetic energy of 10 J. If its speed is doubled, what will its kinetic energy be?

a. The vehicles travel with a momentum of 3,000 kg•km/s in the NW direction.

A truck travels north with a momentum of 2,600 kg•km/s, and a motorcycle heads west with a momentum of 1,500 kg•km/s. The motorcycle hits the truck. If the two vehicles collide and then stick together, what is the momentum and direction of travel? a. The vehicles travel with a momentum of 3,000 kg•km/s in the NW direction. b. The vehicles travel with a momentum of 6,000 kg•km/s in the SW direction. c. The vehicles travel with a momentum of 3,000 kg•km/s in the NW direction. d. The vehicles travel with a momentum of 6,000 kg•km/s in the SW direction.

b. 1/2 as much

A woman can lift barrels a vertical distance of 1 meter or can roll them up a 2-meter long ramp to the same elevation. If she uses the ramp, the applied force required is a. 1/4 as much. b. 1/2 as much. c. the same amount. d. 2 times as much. e. 4 times as much.

b. 30%

About how efficient is a typical gasoline-burning car engine? a. 5% b. 30% c. 70% d. 100%

d. work input equals work output

All simple machines ideally work on the principle that a. impulse equals momentum change. b. force equals mass times acceleration. c. total momentum before a collision equals total momentum after the collision. d. work input equals work output. e. kinetic energy transforms into potential energy.

1.5 m/s

An 8-kg blob of clay moving horizontally at 2 m/s hits a 3-kg blob of clay at rest. What is the speed of the two blobs stuck together immediately after the collision?

8 m

An anvil hanging vertically from a long rope in a barn is pulled to the side and raised like a pendulum 1.60 m above its equilibrium position. It then swings to its lowermost point where the rope is cut by a sharp blade. The anvil then has a horizontal velocity with which it sails across the barn and hits the floor, 10.0 m below. How far horizontally along the floor will the anvil land?

70 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? a. 0 J b. 35 J c. 50 J d. 70 J e. 140 J

a. energy

An object at rest may have a. energy. b. speed. c. velocity. d. momentum. e. none of the above

c. moving

An object that has kinetic energy must be a. at rest. b. falling. c. moving. d. elevated.

e. all of the above

As a pendulum swings back and forth a. at the end points of its swing, its energy is all potential. b. at the lowest part of its swing, its energy is all kinetic. c. kinetic energy is transformed into potential energy. d. potential energy is transformed into kinetic energy. e. all of the above

240 N*s

Assume that a 15-kg ball moving at 8 m/s strikes a wall perpendicularly and rebounds elastically at the same speed. What is the amount of impulse given to the wall?

0 m

At what height does a 1000-kg mass have a potential energy of 1 J relative to the ground?

a. hydrogen

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

e. 75 J

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

e. 600 W

How much power is expended if you lift a 60 N crate 10 meters in 1 second? a. 0 W b. 6 W c. 10 W d. 60 W e. 600 W

c. 8 W

How much power is required to do 40 J of work on an object in 5 seconds? a. 0 W b. 5 W c. 8 W d. 40 W e. 200 W

e. 40 J

How much work is done on a 20-N crate that you lift 2 m? a. 0 J b. 1 J c. 2 J d. 20 J e. 40 J

a. 0 J

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

a. Earth would spin a bit slower.

If all people, animals, trains and trucks all over the world began to walk or run towards the east, then a. Earth would spin a bit slower. b. Earth's spin would not be affected at all. c. Earth would spin a bit faster.

dependent on the mass of the barbell

If possible, determine the power expended when a barbell is raised 5.0 m in 2 s.

d. twice

If you lift two loads up one story, how much work do you do compared to lifting just one load up one story? a. One quarter as much b. One half as much c. The same amount d. Twice as much e. Four times as much

e. force times distance

In physics, work is defined as a. force times time. b. force divided by distance. c. distance divided by time. d. force divided by time. e. force times distance.

300 N

In raising a 3000-N piano with a pulley system, it is noted that for every 2 m of rope pulled down, the piano rises 0.2 m. Ideally, what force is needed to lift the piano?

b. 10 N

It takes 80 J to push a large box 8 m across a floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box? a. 8 N b. 10 N c. 80 N d. 640 N e. none of the above

b. one half the product of its mass times its speed squared

Kinetic energy of an object is equal to a. its mass multiplied by its acceleration squared. b. one half the product of its mass times its speed squared. c. its mass multiplied by its speed. d. one half the product of its mass times its speed. e. its mass multiplied by its acceleration.

c. both kinetic and potential energy

Mechanical energy can be in the form of a. kinetic energy. b. potential energy. c. both kinetic and potential energy. d. neither kinetic nor potential energy.

d. there is no external system acting on the system.

Momentum of a system is conserved only when a. there are no internal forces acting on the system. b. the system is not moving. c. there are no forces acting on the system. d. there is no net external force acting on the system.

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

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

c. zero

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 a. small but noticeable. b. the same as before. c. zero.

c. decreased

Rockets are launched from an airplane in the forward direction of motion. The kinetic energy of the airplane will be a. unchanged. b. increased. c. decreased.

b. 0.7 m

Sue can easily lift a 45.0-N rock with the help of a lever. When she pushes down with 20.0 N of force, she lifts the rock 0.3 meters. How far does she move her arms to do this? a. 0.3 m b. 0.7 m c. 6.0 m d. 2.3 m e. 20.0 m

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

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

3200 N

The 4.0-kg head of an ax is moving at 4.0 m/s when it strikes a log and penetrates 0.01 m into the log. What is the average force the blade exerts on the log?

d. the work done in lifting it

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

a. the exhaust gases

The force that accelerates a rocket into outer space is exerted on the rocket by a. the exhaust gases. b. Earth's gravity. c. atmospheric pressure. d. rocket's wings. e. none of the above

a. impulse acting on it

The momentum change of an object is equal to the a. impulse acting on it. b. velocity change of the object. c. force acting on it. d. force acting on it times its velocity. e. object's mass times the force acting on it.

a. mass times its velocity

The momentum of an object is defined as the object's a. mass times its velocity. b. force times the time interval. c. force times its acceleration. d. mass times it acceleration. e. velocity times the time interval.

e. mechanical advantage

The ratio of output force to input force of a simple machine is called the a. fulcrum. b. efficiency. c. pivot point. d. lever arm. e. mechanical advantage.

e. efficiency

The ratio of useful work output to total work input is called the a. mechanical advantage. b. lever arm. c. pivot point. d. fulcrum. e. efficiency.

e. watt

The unit of power is the a. newton. b. meter. c. joule. d. second. e. watt.

c. joule

The unit of work is the a. watt. b. meter. c. joule. d. newton. e. second.

c. zero

Two gliders having the same mass and speed move toward each other on an air track and stick together. After the collision, the velocity of the gliders is a. twice the original velocity. b. one half the original velocity. c. zero. d. the same as the original velocity. e. There is not enough information to say.

b. 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 a. acceleration. b. momentum. c. speed. d. all of the above e. none of the above

270 J

What amount of work is done on a chair that is pushed 9 m across a floor by a horizontal 30-N net force?

400 kg.m/s

What is the average momentum of a 50-kg skateboarder who covers 400 m in 50 s?

12,000 J

What is the work done in lifting 60 kg of blocks to a height of 20 m?

1000 J

What is the work done in raising a 20-kg block 5 m vertically?

d. increases by nine times

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

a. the 60 km/h car

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

c. the large truck

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

d. a pickup truck traveling down the highway

Which of the following has the largest momentum? a. A large truck parked in a parking lot b. A tightrope walker crossing Niagara Falls c. The science building at your school d. A pickup truck traveling down the highway e. A dog running down the street

c. both require the same amount of work

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

b. he and granny make a bouncing collision wach going in opposite directions.

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 a. Granny catches him and they both move together. b. he and Granny make a bouncing collision, each going in opposite directions.

a. .3

You use a pulley to lift your bike to the ceiling for winter storage. When you bought the pulley, the salesman claimed that the pulley has a mechanical advantage of 10. While lifting the bike, you notice that the pulley is squeaking because it has rusted over the summer. You determine that the pulley now has an actual mechanical advantage of 3. What is its efficiency? a. .3 b. 3 c. 3.33 d. 30