3.3 - Work, Energy and Power

Question 1

Define work done.

Answer 1

The product of the magnitude of the force and the distance moved by the object in the direction of the force. Unit: Joules (J).

Question 2

Define Kinetic Energy and give its SI base unit.

Answer 2

The energy associated with the motion of an object with mass.
The SI base unit is kgm²s⁻²

Question 3

Define Gravitational Potential Energy.

Answer 3

The energy of an object due to its position in a gravitational field.

Question 4

Define Elastic Potential Energy.

Answer 4

The energy stored by an object as a result of a reversible change in its shape.

Question 5

State the principle of conservation of energy.

Answer 5

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

Question 6

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

Answer 6

All initial GPE is converted to KE as the object falls, and this KE is converted back to GPE as it rises.
Equating KE and GPE gives: mgh = ½ mv²
Rearranging this in terms of v² gives v²= 2gh, so v = √2gh
Since there is no ‘m’ in the calculation, the mass has no effect on the final speed – the acceleration of free fall is the same for all object

Question 7

The rate of work done is equal to…

Answer 7

Power.

Question 8

What is efficiency?

Answer 8