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

Question 2

Define kinetic energy and give its SI unit

Answer 2

The energy associated with the motion of an object with mass. kgm^2s^-2

Question 3

Define gravitation potential energy

Answer 3

The energy of an object due to Optus 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 gravitation 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 the equation
Rearrange to get v
Since there is no’m’ in calculated, mass has no effect on the final speed- acceleration of free fall is the same for all objects

Question 7

What is rate of work done?

Answer 7

Power

Question 8

What is efficiency?

Answer 8

useful output power/ total input power x 100