S-Cool Revision Summary

S-Cool Revision Summary

Power

Work done = mgh

Power is defined as the rate at which you do work.

Units: W, watts. 1 watt = 1 joule per second (= 1 Js-1)

The equation is:

Power = Work Done / Time Taken

Another useful equation can be derived from this. Notice that:

Work done, W = force x displacement =Fs

So power = Copyright S-cool or Copyright S-cool

And Copyright S-cool

So P =Fv

So Power = Force x velocity; remembering that the force and velocity must be in the same direction.

Internal energy

If you look at the atoms that make up everything or anything, they are moving around (more at higher temperatures) and feeling forces acting on them due to their neighbours (attraction and repulsion).

This means that the atoms themselves have got kinetic energy (K.E.) and potential energy (P.E.). This is known as the atoms internal energy.

You need to know that the internal energy, U, of a substance is made up of two components.

U = K.E. + P.E. = Ek + Ep

Equations and Definitions

W = F s

Work = force x distance moved in the direction of the force

Copyright S-cool

Power is the rate at which you do work.

Copyright S-cool

Ep = mgh

Copyright S-cool

U = Ek + Ep

Symbols

W = work done, J

F = force, N

s = displacement, m

t = time, s

v = velocity, ms-1

K.E. or Ek = kinetic energy, J

Ep = potential energy, J

u = internal energy, J