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Chapter 9 Energy - Conceptual Physics

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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)
joule
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)
fulcrum
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
actual mechanical advantage/ theoretical mechanical advantage