Forces

A force can be defined as a push or a pull. Force can either cause an object to increase its speed or just move. Symbol of force is the newton(N). Force is a vector quantity.

Types of force:

• Gravitational
• Electric
  
• Nuclear
• Magnetic

Moments

The moment of a force is simply the product of the force and the perpendicular distance. The SI unit of moment is Newton metre(NM)

Formula for finding moments:

Moment = Force x perpendicular distance

Principle of Moments

The principle of moments states that the sum of the clockwise moments about any point is equal to the sum of the anti- clockwise moments about that point.

Centre of gravity

The centre of gravity of a body is defined as that point in the body at which all its weight acts.

Clockwise = Anticlockwise
W x d = W x d

Hook's Law

Hooke's law states that the force does not cause the material to remain permanently stretched then the extension (x) is proportional to the force applied.

F = Kx

where K is the force required to extend the material by one metre

elasticity refers to the stretching of objects(rubber band, springs) when pulled and returning to their original length when force is released.