5. Work, energy and power

Question 1

Define work done

Answer 1

work is done when an object is moved over a distance by an external force applied in the direction of its displacement.
W= F X d
work= force applied in direction of displacement x displacement

Joules= N x m

Question 2

What is the principle of conservation of energy?

Answer 2

Energy cannot be created or destroyed, it can only change from one form to another.

Question 3

What are all the types of energy-

Answer 3

kinetic- energy of a moving object
gravitational potential- gains when you lift it and loses it when it falls
elastic-energy in stretched spring or elastic band
chemical- energy contained in chemical substance
nuclear- energy contained within the nucleus of an atom
internal-energy something has due to its temperature

Question 4

What are the types of energy that can be transferred-

Answer 4

kinetic
thermal
sound
electrical
light

Question 5

What are the types of energy that can be stored-

Answer 5

elastic
gravitational potential
chemical
nuclear

Question 6

What is energy dissipation:

Answer 6

When energy is transferred from one form to another, not all the energy will end up in the desired form (or place).
Dissipation is used to describe ways in which energy is wasted

Question 7

What is the efficiency of the system?

Answer 7

The efficiency of a system is the ratio of the useful energy output from the system to the total energy input.

Question 8

How to calculate efficiency?

Answer 8

efficiency= useful energy output/ total input x 100%
also
efficiency= useful power output/ total power input x 100%

Question 9

Define power

Answer 9

The power of a machine is the rate at which it transfers energy

Question 10

How to calculate power-

Answer 10

1. power W = energy J/ time s
2. power W= work done J/ time s
3. power W= force N x velocity ms-1
   where force moves a body at constant velocity
   force must be applied in the direction as the velocity