1.Mechanics

Displacement

Displacement

Distance moved in a given direction

Instantaneous speed

Rate of change of distance

Average speed

Rate of change of total distance

Velocity

Rate of change in displacement

Average velocity

Rate of change in net displacement

Acceleration

Rate of change of velocity

Moment of a force

Force x Perpendicular distance from the line of action of the force to the pivot

Couple

A pair of forces that are equal in magnitude but opposite in direction and separated by a perpendicular distance

Moment of a couple

Force × Perpendicular distance between the lines of action of the forces

Centre of mass

The point in a body where the weight appears to act

Principle of moments

For a body in equilibrium the sum of the clockwise moments if equal to the sum of the anticlockwise moments about a point

Newtons first law

An object will remain stationary or moving at a constant velocity unless acted on by a resultant force

Newtons second law

The rate of change of momentum of an object is proportional to the resultant force of the object and in the direction of the resultant force

Newtons third law

When body A exerts a force on body B, body B exerts a equal and opposite force on body A of same type

Inertia

Resistance to change in motion

Momentum

Product of its mass and velocity

Impulse

product of the force and the time for which the force exerts

Principle of momentum

Within a closed system the total momentum in any direction remains constant

Elastic collision

A collision in which the total kinetic energy is conserved

Inelastic collision

A collision in which some or all of the kinetic energy is transferred to other forms

Hooke’s law

The extension is proportional to the force applied provided the elastic limit is not exceeded

Tensile stress

Tensile force per unit cross sectional area

Tensile strain

Ratio of extension to its original length

Young Modulus

Ratio of stress to strain which is constant for a material