1.4 Energy Concept

Define work done

It is the energy transferred in moving an object. It is the product of the magnitude of the force and the distance moved in the direction of the force

What is meant by the energy of a system and what is the unit

The amount of work the system can do.

Unit = Joules

Define what is meant by power

1. The rate of work done

2. The rate of energy transferred

What is the formula for work done and how is angle measured

What is the formula for efficiency

Efficiency = The useful output power / total input power

What is meant by friction

A resistance to motion between an object and a surface or an object moving through a fluid. Friction is a force that acts in the opposite direction to the movement

What is the formula for kinetic energy also define what is kinetic energy

Kinetic energy is the energy associated with the motion of an object with mass

E=1/2mv²

Describe what is gravitational potential energy and give the formula

Gravitational potential energy is the energy stored in an object due to its position in a gravitational field.

E=mgh

Define elastic potential energy and give the formula

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

E=1/2kx²

Where x is the extension and k is the spring constant

What is the principle of conservation of energy

Energy cannot be created or destroyed, it can only be transferred into other forms of energy. Therefore the total energy in a close system will always remain the same

Define the relationship between work and energy

Change of energy = work done

Therefore work done = 1/2mv² - 1/2mu²

When will the work done be at maximum

When theta equals to zero

When will the work done be at minimum

When theta equals to ninety

What are the two units for work done

J or kgm²s^-2

What are the two formula for power

P = W/t

W is work done

P = Fv