3.3 Work, Energy and Power

Question 1

What is work done

Answer 1

When a force is required to provide motion, there is a transfer of energy. The magnitude of this
energy transferred depends on the force required and the distance the object moves as a result of
this force.

Question 2

units of work done

Answer 2

joules. One joule is the work done when a force

of 1 N moves an object 1m in the direction of the force

Question 3

What is the principle of conservation of energy

Answer 3

Energy is the capacity for doing work. It is a scalar quantity, measured in joules. There are several different forms of energy, which are all interchangeable. This means energy can be transferred between different forms

Question 4

Define Kinetic Energy and give its SI base unit.

Answer 4

The energy associated with the motion of an object with mass. The SI base unit is kg m2 s-2

Question 5

Define Gravitational Potential Energy.

Answer 5

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

Question 6

Define Elastic Potential Energy.

Answer 6

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

Question 7

State the principle of conservation of energy.

Answer 7

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

Question 8

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 8

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 = 1⁄2 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 objects.

Question 9

The rate of work done is equal to…

Answer 9

Power.