Ch. 7 & 8 Physics Test

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

....?????????

Kinetic energy of an object is equal to ______ a. 1/2 the product of its mass times its speed squared b. 1/2 the product of its mass times its speed c. mass multiplied by its speed d. mass multiplied by its acceleration e. mass multiplied by its acceleration squared

1/2mv^2

If you lift 2 loads up one story, how much work do you do compared to lifting just one load up one story? a. 4x as much b. 2x as much c. the same amount d. 1/2x as much e. 1/4 as much

2x

If you lift one load up 2 stories, how much work do you do compared to lifting one load up only 1 story? a. 4x as much b. 2x as much c. same d, 1/2 as much e. 1/4 as much

2x as much

A 4-kg bal has a momentum of 12 kg m/s. What is the ball's speed? a. 3 m/s b. 4 m/s c. 12 m/s d. 48 m/s e. none of the above

3 m/s

How may joules of work are done on an object when a force of 10 N pushes it 5 m? a. 50 J b. 10 J c. 5 J d. 2 J e. 1 J

50 J

How much power is required to do 100 J of work on an object in 2 seconds? a. 200 W b. 100 W c. 50 W d. 2 W e. 0 W

50 W

A 2kg ball is thrown at 3m/s. What is the ball's momentum? a. 2kg m/s b. 3 kg m/s c. 6 kg m/s d. 9 kg /s e. none of the above

6 kg m/s

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

70 J

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

A pickup truck traveling down the highway

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

All of the above

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

Both change the direction of the force and multiply the force

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

Efficiency

T or F Impulses are normally smaller when bouncing takes place

F

T or F In physics, the amount of work done on an object is the product of the force exerted on the object times the time the object moves

F

T or F Momentum is a scalar quantity

F

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. the asteroid b. Superman c. they both move at the same speeds

Superman

T or F Automobile dashboards that are padded lengthen the time of impact in case of a collision

T

T or F Impulse is defined as the force exerted on an object times the time it lasts

T

T or F Momentum is defines as an object's mass times its velocity

T

T or F The energy an object has by virtue of its location is its potential energy

T

T or F The energy an object has by virtue of its movement is its kinetic energy

T

T or F The unit of power is the watt

T

T or F The unit of work is called the joule

T

T or F What two objects collide and completely stick together, the collision is said to be inelastic

T

T or F When a baseball player follows through when hitting the ball, the contact time with the ball is stronger

T

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

T

A car traveling along the highly needs a certain about of force exerted on it to stop. More stopping force may be required when the car has _____ a. more mass b. more momentum c. less stopping distance d. all of the above e. none of the above

all of the above

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

all of the above

The force of an apple hitting the ground depends upon _______ a. air resistance on the apple as it falls b. the speed of the apple just before it hits c. the time of impact with the ground d. whether or not the apple bounces e. all of the above

all of the above

A collision is considered elastic if_______ a. there is no sound generates during the collision b. there is no lasting deformation c. the objects that collides don't get hot d. after the collisions, the objects have the same shape as before the collision e. all of the above

all of the above`

Energy is changed from one form to another with no net loss or gain a. always true b. sometimes true c. always false

always true

Which requires more work; lifting a 50kg sack vertically 2 meters or lifting a 25kg sack vertically 4 meters? a. 50kg sack b. 25kg sack c both require the same amount

both require the same amount

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. 0 b. doubled c. quadrupled d. unchanged

doubled

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

energy

Impulse is equal to __________ x ________

force time

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

force times distance

While rollerblading, Granny collides with her tiny grandson Ambrose who is at rest. Ignoring any friction, Ambrose's speed after the collision will be greatest when ______ A. he and Granny make a bouncing collision, each ring separate ways B. Granny catches him and they both move together

he and granny make a bounce collision, each ring separate ways

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

impulse acting on it

The reason padded dashboards are used in cars is that they ________ a. look nice and feel good b. increase the force of impact in a collision c. increase the time of impact in a collision d. decrease the momentum of a collision e. decreases the velocity of the car

increase the time of impact in a collision

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

joule

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

larger truck

Potential Energy is the energy an object has because of its ______ a. speed b. location c. size d. temperature e. density

location

The momentum of an object is defines as the object's ________ a. mass X acceleration b. force X acceleration c. mass X velocity d. force X time interval e. velocity X time interval

mass X velocity

Momentum = __________ x ______

mass x velocity

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

moving

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. twice as large b. the same c. one half as large d. 0 e. four times as large

one half as large

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

power

In order to catch a ball, a baseball player moves his or her hand backward in the direction of the balls motion. Doing this reduces the force on impact on the player's hand principally because _______ a. the velocity of the hand is reduced b. the momentum of impact is reduced c. the time of impact is increased d. the time of impact is decreased e. none of the above

the time of impact is increased

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

the work done in lifting it

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

there is no net external force acting on the system

Compared to a sports car moving at 30 mph, the same sports car moving at 60 mph has ________ a. the same momentum b. twice as much momentum c. four times as much momentum

twice as much momentum

The unit of Power is the ______ a. newton b. watt c. meter d. joule c. second

watt

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

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

Two gliders having the same mass and speeds 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. the same as the original velocity c. one half the original velocity d. 0 e. There is not enough information to say

zero