Physics Unit 5 Work, Energy and Power Notes

1.       Work done = Energy transferred

If a force acts at an angle theta with the horizontal, causing a horizontal displacement of distance s, then

Work done = F cos theta x s

2.       When the object is lifted, the work done = change in gravitational potential energy.

3.       An object at rest is acted upon by a force F to give it a constant acceleration, a.

v^2 = u^2 + 2as

½ mv^2 = mas

KE = Fs = Work done by F

 

GPE to KE conversion:

mgh = ½ mv^2

 

Energy transfers

Efficiency = (useful output energy / total input energy) x 100

Principle of Conservation of Energy: Energy can neither be created nor destroyed. It can only be changed from one form to another.

 

Power = work done per unit time

Power = Force x velocity