Physics Ch. 8 Test

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

efficiency

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

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

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

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

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

The unit of work is the...?

Joule

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

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

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

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