3.3 - Work, energy and power

Define work done

The product of the magnitude of the force and the distance is moved by the object in the direction of the force.

Unit: joules (j)

Define kinetic energy

Energy associated with motion. SI base unit is Kg m^2 s^-2

Define gravitational potential energy

The energy an object possesses due to its position in gravitational field

State the principle of conservation of energy

In a closed system, energy cannot be created or destroyed but only transferred from one form to another.

If we consider a closed system where an object is moving up and down derive a formula for the velocity of an object in a gravitational field

All initial GPE converted to KE as it falls, KE converted to GPE as it rises

Equating KE and GPE = mgh = 1/2mv^2

Rearranging, V^2 = 2gh

Since there is no 'm' in equation mass has no effect on final speed. Acceleration of free fall is the same for all objects.

Rate of work done?

Power.

What is efficiency?

Efficiency = useful output power/ total input power. x100