Work is done when a force moves an object through a distance in the direction of the force. Work (W) is equal to the product of the force (F) and distance (s) moved, or W=Fxs. Energy is the capacity to do work and is also measured in joules. The principle of conservation of energy states that in a closed system, the total amount of energy remains constant. Power is the time rate of doing work and is measured in watts. Power is equal to work done divided by the time taken, or W/t.

1. PHYSICS
WORK, ENERGY AND POWER
Short revision series

2. Work
 Work is done when a force moves a body
through a distance in direction of the force,
and is equal to the product of force and the
distance moved
 W = F x s
 W = F x s cos θ (*when considering angle
of the direction)
 SI Unit = Joule
 A JOULE is when a force of 1N moves a body
a distance of 1m.

3. Work done in a field
 W = F x s
 W = mgs

4. Energy
 Capacity to do work
 Also measured in J
 Principle of conservation of energy = in a
closed system the total amount of energy is
constant
Mechanical energy can be K.E or P.E
K.E = ½ mv2
P.E = F x s= mgh

5. Law of conservation of mechanical
energy
 P.E + K.E = constant
 P.E + K.E at point A = P.E + K.E at point B
 ½ mv2 = mgh

6. Power
 Time rate of doing a work measured in watts
W.
 = work done = F x s = F x s/t =Force x velocity
time taken t