# Chapter 9 Energy - Conceptual Physics

### 19 terms by rachel_dunaway

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### work

the product of the net force on an object and the distance through which the object is moved (force x distance)

unit of work

### power

the rate at which work is done

### watt

joule per second. Unit of power

### energy

the property of an object or system that enable it to do work

### mechanical energy

energy due to the position or movement of something (kinetic and potential)

### potential energy

energy that is stored and held at readiness

### elastic potential energy

a stretched or compressed spring

### chemical energy

any substance that can do work through chemical reactions

### gravitational energy

energy due to elevated positions
weight x height
PE = mgh

### kinetic energy

energy of motion
depends on mass and speed
equals half the mass x the square of the speed
KE = 1/2 mv^2

### kinetic energy of a moving object

equal to the work required to bring it to its speed from rest, or the work the object can do while being brought to rest
net force x distance = KE
Fd = 1/2mv^2

### work energy theorem

relationship between work and energy
whenever work is done energy changes
work = ^KE

### law of conservation of energy

energy cannot be created or destroyed. it can be transformed from one form into another, but the total amount of energy never changes

### machine

device used to multiply forces or change direction of forces
cannot put out more energy than is put in it
transfers energy to one place or another or transforms it from one form to another

### lever

simple machine made of a bar that turns about a fixed point
work input - work output
Fd(in) = Fd(out)

pivot point

### pulley

kind of lever that can be used to change the direction of a force

### efficiency

ratio of useful energy output to total energy input
useful work output/ total work input

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