Understanding Work and Energy

Work
1. Work is defined as the product of the applied force and the displacement of an object in the direction of the applied force.
2. W = F x d
3. W= work done, F = force applied, d = displacement in the direction of force.
4. SI unit for work = Joule (J), other unit = Nm
5. Work is not done when:

• The object is stationary or not moving
• No force is applied on the object in the direction of displacement.
• The direction of motion of the object is perpendicular to that of the applied force.

6. When work is done to an object, energy is transferred to the object.


Energy (Energy is the capacity to do work)
1. Energy exists in different forms: kinetic energy, gravitational potential energy, elastic potential energy, sound energy, heat energy, light energy, electrical energy and chemical energy.
2. The unit for energy is Joule (J) – same as work
3. The work done is equal to the amount of energy transferred.
4. Kinetic energy is the energy of an object due to its motion.
5. Kinetic energy or work done is given by:

• a. ½ mv²
• b. M = mass, v = velocity
• c. Unit: Joule

6. Gravitational potential energy is the energy of an object due to its higher position in the gravitational field.

• E = mgh
• M = mass, g = acceleration due to gravity, h = height in metre