Turning effect of forces

Accelerates an object

Decelerates an object

change the direction of an object

change the shape of an object

move a stationary object

stop a moving object

1st law of motion

balanced forces

Body continues to move at constant spped in a straight line unless an unbalanced force acts on it.

2nd law of motion

unbalanced forces

Net F=ma

3rd law of motion

action-reaction forces

occurs when 2 forces are present

contact force

always act in an opposite direction to the force applied on an object

Definition: The centre of gravity(CG) of a body is that point where the whole weight of the body seems to act

Centre of gravity of a irregular-shaped object

centre of gravity is always vertically below the pivot(point of suspension) when it is hanging freely about it

Centre of gravity of a regular-shaped object

E.g metre rule. The centre of gravity is its centre(or geometrical centre)

Definition: The moment of a force is the turning effect of a force about a point

The turning effect(or moment) of a force depends on

a) Magnitude of the force

b) Perpendicular distance between the point of the application of the force and the pivot

When a body is in equilibrium, the sum of clockwise moments about the balance point or pivot = to the sum of anti-clokwise moments about the same point

Total clockwise moments about the same point = total anti-clockwise moments about a point

Stable equilibrium

when a body is able to return to its original position after being displaced slightly

Unstable equilibrium

when a body continues to move away from its original position after it is being slightly displaced

Neutral equilibrium

when a body remanis wherever it is displaced

Definition: The moment of a force(M) about a point or pivot(O) is the product of the force(F) and the perpendicular distance(d) from the line of action of the fprce to the point/pivot.

Moment of a Force= F x d