Turning Forces

You know that forces are a push or pull A turning force is another force you come across in everyday life Opening a Coke can, turning a door handle, or a tap, using a tin opener

The See Saw There are two turning forces on a see saw The principle of moments states that if a see saw is balanced the clockwise moments are equal to the anti- clockwise moments Clockwise MomentAnti-Clockwise Moment Pivot

Turning Forces Turning Forces are called Moments To work out a moment you use F FF Force (N) x Distance from the Pivot (m) The units for moments are Newton metres (N m) Moments can turn clockwise or anti- clockwise

The See-Saw The see saw is not balanced, because they are both the same distance from the pivot This means that the heavier kid has the biggest turning force

The See-Saw Now it is balanced (in equilibrium) because the bigger kid is close to the pivot giving him a smaller turning force The further away from the pivot the bigger the turning force

Questions on Moments If the see saw is balanced, how far from the pivot is the 20N? 10 N 5 m 20 N 10m 5m 20 N 10 N 10m How much force is needed to balance the anti- clockwise side? 2.5m 20 N

More Questions on Moments What are moments measured in? Newton metres Work out if the following is balanced: 20 m15m 5 N 7.5 N Anti- clockwise moment = Clockwise moment F x D = F x D 5 x 20 = 7.5 x N m = N m No it is not balanced it tips clockwise with a moment of 12.5 N m

Levers If you wanted to open this tin you would use a lever This screwdriver is too small to open the lid This crowbar is bigger so it can multiply the force you exert It makes work easier

Labelling Lever Diagrams Our body joints have levers The pivot can also be called the fulcrum

The Wheelbarrow This wheelbarrow can lift more than we can The lever from the handles to the fulcrum multiplies our effort

Questions on Levers What is the other name for the pivot? The fulcrum Look at the nutcracker, where is the pivot, load and effort Pivot Effort Load

Stability Formula 1 cars have a low centre of gravity so that they don’t topple over Maradona had a low centre of gravity allowing him to turn quickly Stable objects are difficult to knock over

Making something stable Give it a wide base

How to make things stable Give it a low centre of gravity

Unstable objects The unicyclist has a high centre of gravity The tightrope walker needs the pole to lower his centre of gravity Ice Skates have a narrow base

Questions on Stability Sort these shapes according to their stability starting with the most stable In each of the following diagrams the arrow is the centre of gravity, will these shapes fall over?

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