Physics Chapters 7,8 (Due Nov

Physics Chapters 7,8 (Due Nov. 21, Test Nov. 22)

Multiple Choice

Identify the choice that best completes the statement or answers the question.

____1.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.

____2.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

____3.Compared to a sports car moving at 30 miles per hour, the same sports car moving at miles per hour has

a. / twice as much momentum.
b. / four times as much momentum.
c. / the same momentum.

____4.If the momentum of an object changes and its mass remains constant,

a. / it is accelerating (or decelerating).
b. / there is a force acting on it.
c. / its velocity is changing.
d. / all of the above
e. / none of the above

____5.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.

____6.In order to increase the final momentum of a golf ball, we could

a. / increase the force acting on it.
b. / follow through when hitting the ball.
c. / increase the time of contact with the ball.
d. / swing as hard as possible.
e. / all of the above

____7.The reason padded dashboards are used in cars is that they

a. / look nice and feel good.
b. / decrease the impulse in a collision.
c. / increase the force of impact in a collision.
d. / decrease the momentum of a collision.
e. / increase the time of impact in a collision.

____8.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.

____9.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.

____10.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.
e. / the system has zero momentum.

____11.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

____12.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

____13.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

____14.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

a. / zero.
b. / unchanged.
c. / quadrupled.
d. / doubled.

____15.A cannon recoils from launching a cannonball. The speed of the cannon's recoil is small because the

a. / impulse on the cannon is less than the impulse on the cannonball.
b. / cannon has far more mass than the cannonball.
c. / momentum of the cannon is unchanged.
d. / force against the cannon is relatively small.
e. / none of the above

____16.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

a. / the time of impact is decreased.
b. / the time of impact is increased.
c. / the velocity of the hand is reduced.
d. / the momentum of impact is reduced.
e. / none of the above

____17.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

____18.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

____19.The force of an apple hitting the ground depends upon

a. / the speed of the apple just before it hits.
b. / the time of impact with the ground.
c. / whether or not the apple bounces.
d. / air resistance on the apple as it falls.
e. / all of the above

____20.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.

____21.A 1-N apple falls to the ground. The apple hits the ground with an impact force of

a. / 1 N.
b. / 2 N.
c. / 4 N.
d. / 9.8 N.
e. / Not enough information to say

____22.A karate expert executes a swift blow and splits a cement block with her bare hand.

a. / The forces on both the block and the expert's hand have the same magnitude.
b. / The times of impact on both the block and the expert's hand are the same.
c. / The impulses on both the block and the expert's hand have the same magnitude.
d. / all of the above
e. / none of the above

____23.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

a. / zero.
b. / one half as large.
c. / the same.
d. / twice as large.
e. / More information is needed to say.

____24.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.

____25.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.

____26.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

____27.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.

____28.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

a. / the astronaut's time between catches will decrease as the game progresses.
b. / the astronaut will never catch the first bounce.
c. / the astronaut will catch one bounce only.
d. / none of the above

____29.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.

____30.Superman is at rest in space when he throws an asteroid that has more mass than he does. Which moves faster, Superman or the asteroid?

a. / Superman
b. / The asteroid
c. / They both move at the same speed.

____31.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

____32.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.

____33.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).

____34.A 2-kg ball is thrown at 3 m/s. What is the ball's momentum?

a. / 2 kg·m/s
b. / 3 kg·m/s
c. / 6 kg·m/s
d. / 9 kg·m/s
e. / none of the above

____35.A 4.0-kg ball has a momentum of 20.0 kg·m/s. What is the ball's speed?

a. / 0.2 m/s
b. / 5.0 m/s
c. / 20.0 m/s
d. / 80.0 m/s
e. / none of the above

____36.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.

____37.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.

____38.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

____39.If you lift one load up two stories, how much work do you do compared to lifting one load up only 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

____40.If Nellie Newton pushes an object with twice the force for twice the distance, she does

a. / twice the work.
b. / the same work.
c. / four times the work.
d. / eight times the work.

____41.The unit of work is the

a. / watt.
b. / meter.
c. / joule.
d. / newton.
e. / second.

____42.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.

____43.The unit of power is the

a. / newton.
b. / meter.
c. / joule.
d. / second.
e. / watt.

____44.Potential energy is the energy an object has because of its

a. / density.
b. / size.
c. / location.
d. / speed.
e. / temperature.

____45.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.

____46.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.

____47.How much farther will a car traveling at 100 km/s skid than the same car traveling at 50 km/s?

a. / Half as far.
b. / The same distance.
c. / Twice as far.
d. / Four times as far.
e. / Five times as far.

____48.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

____49.Energy is changed from one form to another with no net loss or gain.

a. / Sometimes true
b. / Always false
c. / Always true

____50.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

____51.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

____52.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. / as much.
b. / as much.
c. / the same amount.
d. / 2 times as much.
e. / 4 times as much.

____53.A job is done slowly, and an identical job is done quickly. Both jobs require the same amount of work but different amounts of

a. / energy.
b. / power.
c. / both A and B
d. / none of the above

____54.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.

____55.An object that has kinetic energy must be

a. / at rest.
b. / falling.
c. / moving.
d. / elevated.

____56.An object that has kinetic energy must have

a. / acceleration.
b. / a force applied to maintain it.
c. / momentum.
d. / none of the above

____57.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

____58.A person on a roof throws one ball downward and an identical ball upward at the same speed. The ball thrown downward hits the ground with 140 J of kinetic energy. Ignoring air friction, with how much kinetic energy does the second ball hit the ground?

a. / less than 140 J
b. / 140 J
c. / 280 J
d. / more than 280 J
e. / none of the above

____59.An object at rest may have

a. / energy.
b. / speed.
c. / velocity.
d. / momentum.
e. / none of the above

____60.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

____61.If an object has kinetic energy, then it also must have

a. / impulse.
b. / force.
c. / momentum.
d. / acceleration.
e. / none of the above

____62.If the velocity of a moving object doubles, then what else doubles?

a. / acceleration.
b. / kinetic energy.
c. / momentum.
d. / all of the above
e. / none of the above

____63.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.

____64.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.

____65.A pulley system can

a. / change the direction of a force.
b. / multiply the force.
c. / increase the amount of work done.
d. / Both A and B
e. / Both B and C

____66.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.

____67.About how efficient is a typical gasoline-burning car engine?

a. / 5%
b. / 30%
c. / 70%
d. / 100%

____68.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 more kinetic energy is the

a. / the limousine.
b. / the small economy car.
c. / neither one—they receive the same amount of kinetic energy.

____69.A popular toy consists of an aligned row of identical elastic balls suspended by strings so they touch each other. When two balls on one end are elevated and released, they slam into the array of balls and two balls pop out the other side. If instead, one ball popped out with twice the speed, this would be a violation of the conservation of

a. / both energy and momentum.
b. / energy.
c. / momentum.

____70.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.

____71.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

____72.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

____73.Suppose a moving car has 3000 J of kinetic energy. If the car's speed doubles, how much kinetic energy will it then have?

a. / 1000 J
b. / 1500 J
c. / 3000 J
d. / 6000 J
e. / 12,000 J

____74.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

____75.A 60-N object moves at 1 m/s. Its kinetic energy is

a. / 1 J.
b. / 3 J.
c. / 60 J.
d. / more than 60 J.

____76.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

____77.A pulley has two supporting strands. In order for it to lift a load 1 meter, the person pulling will have to pull a distance of

a. / m.
b. / m.
c. / 1 m.
d. / 2 m.
e. / 4 m.

____78.A frictionless inclined plane is 8.0 m long and rests on a wall that is 2.0 m high. How much force is needed to push a block of ice weighing 300.0 N up the plane?

a. / 37.5 N
b. / 75.0 N
c. / 100.0 N
d. / 300.0 N
e. / 600.0 N

____79.A certain jack has a theoretical mechanical advantage of 300. However, due to frictional forces, the actual mechanical advantage is only 100. What is the efficiency of the jack?

a. /
b. /
c. / 30
d. / 300
e. / 30,000

____80.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

Problem