# Physics Unit 3 - Moments, stability, lenses. AQA

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• Created by: Jess
• Created on: 04-05-10 19:40

Moments

The turning effect of a force.

Moment (in Newton metres) = Perpendicular distance for pivot (in Metres) x Force (In newtons. So to balance each side must be equal.

To work out a moment - Times the left hand side M by the N going down then the same with the right. Then times them together!

If the total anticlockwise moments DOES NOT equal the Total Clockwise Moment, there will be resultant moment so the object will turn.

Stability

Centre Of Mass - Point at which all the mass is said to act.

For an object to be stable the centre of gravity must fall within the object - always acts DOWN.

Circular Motion - Velocity is constantly changing

Velocity is both the speed and direction of an object

If an object is travelling in a circle its CONSTANTLY CHANGING DIRECTION which means its accelerating.

must be a force acting on it which acts towards the centre of the circle. This is the CENTRIPETAL force which keeps something moving in a circle.

But what provides the centripetal force?

It can be tension, friction or even gravity. Its what keeps it going. A car going round the bend is kept on the road by FRICTION, the centripetal force. A bucket on a rope is kepts spinning by TENSION and so on.

Centripetal force depends on MASS, SPEED and RADIUS.