question

the power required to exert a 4-N force over 3 meters in 2 seconds is

answer

4(3)=12/2= 6
6 W

question

the work you do when pushing a shopping cart twice as far while applying twice the force is

answer

four times as much

question

hydro and wind power are indirect forms of

answer

solar energy

question

a roller skate at rest may have

answer

energy

question

relative to an initial height, an object raised twice as high has a gravitational potential energy that is

answer

twice as much

question

when Joshua brakes his speeding bicycle to a stop, kinetic energy is transformed to

answer

heat

question

a hydraulic jack is used to lift objects such as automobiles. If the input force is 200 N over a distance of 1 meter, the output force over a distance of 0.1 meter is ideally

answer

f x d
200(1)=f(.1)
200/.1=2000
2000 N

question

an object that has kinetic energy must be

answer

moving

question

a 2 kg ball is held 4m about the ground. Relative to the ground its potential energy is

answer

mgh
2(10)(4)= 80
answer- 80

question

two identical arrows, one with twice the speed of the other, are fired into a bale of hay. Compared with penetration of the slow arrow, the faster arrow penetrates

answer

four times as far

question

which task requires more work
a. lifting the 25 kg sack 4 meters
b. both the same
c. lifting the 50 kg sack 2 meters
d. need more information

answer

B. both the same

question

the power expended doing 100J of work in 50 s is

answer

2 W

question

a crate of grapes lifted 10 meters gains 200 J of potential energy. If the same crate is instead lifted 20 meters, its gain in potential energy is

answer

twice as much

question

a machine puts out 100 watts of power for every 1000 watts put into it. The efficiency of the machine is

answer

100/1000=.1= 10%

question

a ball rolling down an incline has its maximum kinetic energy at

answer

the bottom

question

if a ping pong ball and a golf ball both move in the same direction with the same amount of kinetic energy, the speed of the ping pong ball must be

answer

more than the golf ball

question

two identical arrows, one with twice the kinetic energy of the other, are fired into a bale of hay. Compared with penetration of the slow arrow, the faster arrow penetrates

answer

twice as far

question

a hydraulic press has its input piston depressed 20 cm while the output piston is raised 1 cm. A 1 N input can lift a load of

answer

20 N

question

which has greater kinetic energy
a. a car half the mass traveling at 60 km/hr
b. need more information
c. a car traveling at 30 km/hr
d. both the same

answer

a. a car half the mass traveling at 60km/hr

question

a 2 kg box of taffy candy has 40 J of potential energy relative to the ground. Its height above the ground is

answer

PE= mgh
2(10)(h)=40
20=40
40/20=2
2 m

question

danny diver weighs 500 N and steps off a diving board 10 m above the water. Danny hits the water with kinetic energy of

answer

more than 5000 J

question

about 40 J is required to push a crate 4 m across a floor. If the push is in the same direction as the motion of the crate, the force on the crate is about

answer

10 N

question

a ball rolling down an incline has its maximum potential energy at

answer

the top

question

an object has gravitational potential energy due to its

answer

location

question

a primary difference between momentum and kinetic energy is

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momentum can cancel; KE energy cannot

question

strictly speaking, more fuel is consumed by your car if the air conditioner, headlights, or even a radio is turned on. This statement is

answer

true only if the car's engine is running

question

when wind encounters a wind turbine that produces energy, wind speed on the downside of the blades is

answer

speed up

question

phil applies 100 N to a pulley system and raises a load one-tenth of his downward pull. Ideally, the weight of the load is

answer

1000 N

question

a toy elevator is raised from the ground floor to the second floor in 20 seconds. The power needed using 1000 J of work is

answer

1000/20
50 W

question

both a 50 kg sack is lifted 2 meters from the ground and a 25 kg sack is lifted 4 meters in the same time. The power expended in raising the 50 kg sack is

answer

50(2)=100
25(4)= 100
the same

question

a jack system will increase the potential energy of a heavy load by 1000 J with a work input of 2000 J. The efficiency of the jack system is

answer

1000/2000=.5=50%
50%

question

a clerk can lift cylindrical packages 1 meter vertically, or can roll them up a 2 meter long ramp to the same elevation. With the ramp, the applied force required is about

answer

half as much

question

two identical golf carts move at different speeds. The faster cart has twice the speed and therefore has

answer

four times the kinetic energy

question

the work you do when pushing a shopping cart a given distance while applying twice as much force is

answer

four times as much

question

when a drawn bow of potential energy 40 J is fired, the arrow will ideally have a kinetic energy

answer

more than 40 J

question

the work you do when pushing a shopping cart twice as far while applying the same force is

answer

twice as much

question

the bob of a simple pendulum has its maximum kinetic energy at the

answer

bottom of its swing

question

a 1000 kg car and a 200 kg car are hoisted to the same height. Raising the more massive requires

answer

twice as much work

question

two 2-m/s pool balls roll toward each other and collide. Suppose after bouncing apart each moves at 4m/s. this collision violates the conservation of

answer

energy

question

a circus diver drops from a high pole into water far below. When he is halfway down a. he has gained an amount of kinetic energy equal to has his initial PE
b. none of the choices
c. all choices are correct
d. his PE is halved
e. his KE and PE are equal

answer

c. all choices are correct

question

a 2500 N pile driver ram falls 10 m and drives a post 0.1 m into the ground. The average impact force on the ram is

answer

2500(10)=25000/.1=250,000
250,000 N

question

earths primary energy source is

answer

the sun

question

the work done is pushing a TV set a distance of 2m with an average force of 20 N is

answer

W=fd
20(2)
40 J