Work and Energy Practice Questions

A 0.002 kg coin, which has zero potential energy at rest, is dropped into a 10.0 m well. After the coin comes to a stop in the mud, what is its potential energy?

-0.196 J

A hill is 100 m long and makes an angle of 12 with the horizontal. As a 50 kg jogger runs up the hill, how much work does gravity do on the jogger?

-10 000 J

a girl can easily lift an 80-N rock with the help of a type 1 lever. Whenn she pushes down with 10 M of force, she lifts the rock .1 meters. How far does she move her arms to do this?-10;8; 1; .8; .1

.8

how much work is done on a 50-N rock that you carry horizontally across a 10-m room?-10; 5; 50; 0; 500

0

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

a certain jack has a theoretical mechanical advantage of 500. However, due to frictional forces, the actual mechanical advantage is only 100. What is the efficiency of the jack?-500; 5; 50,000; 50; 1/5

1/5

a machine puts out 100 watts of power for every 1000 watts put into it. The efficiency of the machine is _____. -10%; 90%; 110%; 50%

10%

a frictionless inclined plane is 6m long and rests on a wall that is 2m high. How much force is needed to push a block of ice weighing 300 N up the plan?-50 N; 300 N; 100 N; 200 N; 600 N

100 N

What is the kinetic energy of a 0.135 kg baseball thrown at 40.0 m/s?

108 J

A 40.0 N crate is pulled up a 5.0 m inclined plane at a constant velocity. If the plane is inclined at an angle of 37 to the horizontal and there is a constant force of friction of 10.0 N between the crate and the surface, what is the net gain in potential energy by the crate?

120 J

a pulley has two supporting strands. In order to use it to lift a load 1 meter, the person pulling will have to pull a distance of _______.-1; 2; 1/4; 4; 1/2

2

A horizontal force of 200 N is applied to move a 55 kg television set across a 10 m level surface. What is the work done by the 200 N force on the television set?

2000 J

The magnitude of the component of the force that does the work is 43.0 N. How much work is done on a bookshelf being pulled 5.00 m at an angle of 37.0 from the horizontal?

215 J

A construction worker pushes a wheelbarrow 5.0 m with a horizontal force of 50.0 N. How much work is done by the worker on the wheelbarrow?

250 J

If both the mass and the velocity of a ball are tripled, the kinetic energy of the ball is increased by a factor of

27

A 3.00 kg toy falls from a height of 10.0 m. Just before hitting the ground, what will be its kinetic energy? (Disregard air resistance. g = 9.81 m/s2.)

294 J

A worker pushes a wheelbarrow with a horizontal force of 50.0 N over a level distance of 5.0 m. If a frictional force of 43 N acts on the wheelbarrow in a direction opposite to that of the worker, what net work is done on the wheelbarrow?

35 J

A 1.00 103 kg sports car accelerates from rest to 25.0 m/s in 7.50 s. What is the average power output of the automobile engine?

41.7 kW

A flight attendant pulls a 50.0 N flight bag a distance of 250.0 m along a level airport floor at a constant speed. A 30.0 N force is exerted on the bag at an angle of 50.0 above the horizontal. How much work is done on the flight bag?

4820 J

how many joules of work are done on an object when a force of 10 N pushes it 5m?-50; 10; 1; 2; 5

50

how much power is required to do 100 j of work on an object in 2 seconds>-0; 50; 2; 200; 100

50

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?-140 J; 0; 35; 70; 50

70

A 5.00 102 N crate is at the top of a 5.00 m ramp, which is inclined at 20.0 with the horizontal. What is its potential energy? (g = 9.81 m/s2.)

855 J

Which of the following energy forms is involved in winding a pocket watch?

Elastic potential energy

T/F: a pulley system can only change direction; it can't multiply forces as well

False

T/F: the ratio of output force to input force for a simple machine is its efficiency

False

Which of the following energy forms is associated with an object due to its position relative to Earth?

Gravitational potential energy

The unit of work is the...?

Joule

Which of the following energy forms is associated with an object in motion?

Kinetic energy

Why doesn't the principle of mechanical energy conservation hold in situations when frictional forces are present?

Kinetic energy is not simply converted to a form of potential energy.

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

Potential

Which of the following is the rate at which energy is transferred?

Power

If the only force acting on an object is friction during a given physical process, which of the following assumptions must be made in regard to the object's kinetic energy?

The kinetic energy decreases.

As an object is lowered into a deep hole in the ground, which of the following assumptions must be made in regard to the object's potential energy?

The potential energy decreases.

T/F: The unit of power is the watt

True

T/F: The unit of work is called a joule

True

T/F: using an incline plane is an effective way to lift a heavy object that you couldn't otherwise lift

True

the unit of power is the _______.

Watt

a pulley system can ______.-change the direction of a force; multiply the force; increase the amount of work done; A and B

a and b

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. 0 J

You use a pulley to lift your bike to the ceiling for winter storage. When you brought the pulley, the salesman claimed that the pulley has a mechanical advantage of 10. While lifting the bike, you notice over the summer. You determine that the pulley now has an actual mechanical advantage of 3. What is it efficiency? a. 0.3 b. 3 c. 3.33 d. 30

a. 0.3

A certain jack has a theoretical mechanical advantage of 300. However, due to frictional forces, the actual mechanical advantage is only 100. What is efficiency of the jack? a. 1/3 b. 3 c. 30 d. 300 e. 30,000

a. 1/3

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%

a. 10%

An object at rest may have a. energy b. speed c. velocity d. momentum

a. energy

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

b. 0.7 m

A woman can lift barrels a vertical distance of 1 meter or can roll them up 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. 1/2 as much

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

b. 10 N

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

b. 140 J

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

b. 3 J

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 weighting 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

b. 75.0 N

When a worker shovels coal into the furnace of a train engine, energy is released from the coal as heat. The heat is used to make steam, which is then used to turn the wheels to the engine. Living cells can also be thought of as machines. What biological process uses combustion to release energy from molecules so that cells can do work? a. photosynthesis b. metabolism c. mitosis d. anabolism

b. metabolism

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

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

The equation for determining gravitational potential energy is PEg = mgh. Which factor(s) in this equation is (are) NOT a property of an object?

both g and h

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

c. 8 W

Mechanical energy can be in the form of a. kinetic energy b. potential energy c. both d. neither

c. both

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

c. four times the work

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

c. joule

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

c. location

If an object has kinetic energy, then it also must have a. impulse b. force c. momentum d. acceleration e. none of the above

c. momentum

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

c. moving

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

Which of the following energy forms is NOT involved in hitting a tennis ball?

chemical potential energy

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

d. 2 m

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

d. 70 J

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

d. both a and b

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

d. four times as far

When a car's speed triples, its kinetic energy a. remains the same b. triples c. increase by four times d. increase by nine times

d. increase by nine times

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

d. the work done in lifting it

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

d. twice as much

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

d. twice as much

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

d. work input equals work output

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

e. 12,000 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

e. 40 J

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

e. 600 W

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. 75 J

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

e. efficientcy

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

e. force times distance

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

e. mechanical advantage

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

e. watt

the ratio of useful work output to total work output is called the ______.-lever arm; fulcrum; mechanical advantage; pivot point; efficiency

efficiency

Which form of energy is involved in weighing fruit on a spring scale?

elastic potential energy

Which of the following energy forms is stored in any compressed or stretched object?

elastic potential energy

an object at rest may have ______-speed; momentum; energy; velocity

energy

T/F: the rate at which work is done is called energy

false

T/F: the ratio of useful work output to total work input is mechanical advantage

false

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

force times distance

how much farther will a car traveling at 100 km/s skid than the car traveling at 50 km/s?-twice as far; half as far; the same distance; four 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

A force does work on an object if a component of the force

is parallel to the displacement of the object.

The main difference between kinetic energy and potential energy is that

kinetic energy involves motion and potential energy involves position.

potential energy is the energy an object has because of its ______-location; density; temperature; size; speed

location

the ratio of output force to input force of a simple machine is called the ________-efficiency; lever arm; fulcrum; mechanical advantage; pivot point

mechanical advantage

an object that has linear kinetic energy must be______-at rest; at an elevated position; moving

moving

kinetic energy of an object is equal to ______.-its mass multiplied by its acceleration; one half the product of its mass times its speed squared; its mass multiplied by its acceleration squared; its mass multiplied by its speed; one half the product of its mass times its speed

one half the product of its mass times its speed squared

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 power and energy

power

which requires more work: lifting a 50 kg sack vertically two meters or lifting a 25-kg sack vertically 4 meters?-lifting the 25-kg sack; lifting the 50 kg sack; same amount of work

same amount of work

Work is done when

the displacement is not zero.

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

the work done in lifting it

if you lift two loads up one story, how much work do you do compared to lifting just one load up one story?-twice as much; one quarter as much; the same amount; four times as much

twice as much

all simple machines ideally work on the priciple that _________-work input equals work output; total momentum before a collision equals total momentum after the collision; impulse equals momentum change; kinetic energy transforms into potential energy; force equals mass times acceleration

work input equals work output