42 terms

physics exam

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a woman carries a heavy box across a room at a constant speed. how much work does she do on the box while walking?
none
an object may have potential energy because of its
location
an object that has kinetic energy must be
moving
the ball rolling down an incline has its maximum potential energy at
the top
a ball rolling down an incline has its maximum kinetic energy at
the bottom
a hydraulic press, like a wheel and axle, is capable of multiplying force input
always true
a hydraulic press, like an inclined plane, is capable of increasing energy
always false
when a rifle is fired it recoils as the bullet is set in motion. The rifle and bullet ideally acquire equal
amounts of energy but opposite amounts of momentum
the total momentum of a flock of identical birds could be zero only if the birds are
flying in different directions
if you push for a half hour or a whole hour against a stationary wall
no work is done on either case
if an object is raised twice as high, its potential energy will be
twice as much
an open freight car rolls friction free along a horizontal track in a pouring rain that falls vertically. as water accumulates in the car, the car's speed
decreases
two identicial arrows, one with twice the speed of the other, are fired into a hay bale. the faster arrow will penetrate
four times as far as the slower arrow
two identical arrows, one with twice the kinetic energy of the other, are fired into a hay bale. the faster arrow will penetrate
twice as far as the slower arrow.
a car that travels twice as fast as another when braking to a stop will skid
four times as far
if you do work on an object in one-third the usual time, your power output is
three times the usual power output.
which requires the most amount of work by the brakes of a car
slowing down from 100 km/h to 70 km/h
a car moves 4 times as fast as another identical car. compared to the slower car the faster car has
16 times the kinetic energy
if you find that twice as much work is needed to perform a task but it takes as much time, the amount of power required is
unchanged
a 1000-kg car and a 200-kg car are hoisted the same distance. raising the more massive car requires
twice as much work
which has a greater kinetic energy, a car traveling at 30 km/hr of a car of half the mass traveling at 60 km/hr
the 60 km/hr car
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
the same
of you push an object twice as far while applying the same force you do
twice as much work
a 2-kg mass is held 4 m above the ground. what is the approximate potential energy of the mass with respect to the ground
80 j
it takes 40 J to push a large box 4 m across a floor. assuming the push is the same direction as the move, what is the magnitude of the force on the box
10 N
a machine puts out 100 watts of power for every 1000 watts put into it. the efficiency of the machine is
10%
a diver who weighs 500 N steps off a diving board that is 10 m above the water. the diver hits the water with kinetic energy of
5000 J
the power required to exert 1 N force, over a distance of 1 m in 1 second is
1 W
a 2 kg mass has 40 J of potential energy with respect to the ground. Approximately how high is it above the ground
2 m
using 1000 J of work, a toy elevator is raised from the ground floor to the second floor in 20 seconds. the power needed to do this job was
50 w
a pully system raises a 1000-N load 2 meters with 100 N of input force. The efficiency of the system is
not enough information given
an object lifted 10 meters gains 200 J of potential energy. if the same object is lifted 20 meters its potential energy gain is
twice as much
two identical 5000-kg bulldozers roll toward each other on a level road without friction (one at 1m/s, the other at 2m/s) just before they collide, one has a kinetic energy of 2500 J and the other 10000J this instant their total kinetic energy is
12,500 J
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
250,000 N
a TV set is pushed a distance of 2 m with a force of 20 N. how much work is done on the set
40 J
a bow is drawn so that it has 40 J of potential energy. when fired, the arrow will ideally have a kinetic energy that is
40 J
do 100 J of work in 50 s and your power output is
2 W
a car moving at 50 km/hr skids 20 m with locked brakes. how far will the car skid with locked brakes if it were traveling at 150 km/hr
180 m
whereas impulse involves the time that a force acts, work involves the
distance that a force acts
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
50%
40,000 watts are equal to________kilo-watts
40 kilowatts
kinetic energy is a_____quantity, while Momentum is a____quantity
scalar, vector