Turning Forces and Centre of Gravity Chapter 43

A Lever A lever is a rigid body which is free to turn about a fixed point called the fulcrum. Example: Crow bar Wrench

The Moment The moment of a force tells us how much spin or circular motion a force can cause. x Moment of a Force Force Perpendicular distance from the force to the fulcrum

Law of the Lever The law of the Lever states that when a lever is balanced the sum of the clockwise moments equals the sum of the anticlockwise moments.

The Law of the Lever

Centre of Gravity The centre of gravity is the point of an object where all the forces appear to act.

Equilibrium Equilibrium is when an object is balanced and not moving. 3 states of equilibrium: Stable equilibrium Unstable equilibrium Neutral equilibrium

Stable Equilibrium If given a slight push the object will return to the same position.

Unstable Equilibrium If given a slight push the object will not return to the same position.

Neutral Equilibrium If given a slight push the object will return to a similar position.

Stability An object will topple over if its centre of gravity passes outside its base.

Stability Objects are more stable if they have: Examples A wide base Low centre of gravity Examples Bunsen Bus Flower vase