# Physics Triple

Triple Science Physics Topic and Revision

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• Created by: Amy
• Created on: 10-05-11 08:46

## Moments

Use forces to make things turn. The turning effect that the force has is its moment.

The moment is bigger if the force used is bigger.

The moment is bigger if the distance between the force and the pivot (axis of rotation) is bigger.

Moment (Nm) = Force (N) x Distance from the line of action to axis of rotation (m)

If total anticlockwise moment = total clockwise monent the object will not turn.

If all the mass of an object is concentrated to a point it would be the centre of mass.

For any symmetrical object, the centre of mass is always on the axis of symmetry.

If there are more lines of symmetry the centre of mass is where the lines cross.

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## Key Words

Axis of rotation: The line around which the object spins.

Centre of mass: The point in a body at which the mass of a system may be considered to be concentrated.

Force: A force is a push or pull which is able to change the velocity or shape of a bidy. Forces only exist between bodies. Every force that acts on a body causes an equal opposite reaction from the body.

Moment: The moment of a force acting on one side of a balanced bar is the force multiplied by the distance to the pivot.

Turning effect: the force that tends to make an object spin. The turning effect of a force depends on the size of the force and how far it is from the turning point.

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## Stability

Stability tells us how likely it is that an object will topple over. Stable objects do not topple over easily.

The more unstable an object is, the more easily it topples. It depends on the centre of mass and shape.

When an object is not toppling over, scientists say it is in equilibrium.

The weight acting downwards from the centre of mass may cause a resultant moment about the edge of the base, which makes the object topple over.

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## Key Words

Equilibrium: Where the forward and backward forces are equal.

Resultant moment:the moment produced when a combination of forces act on the same body.

Stability:A measure of the likelihood of change.

Stable: Unlikely to change. Stable systems are less likely to change then unstable.

Unstable: A condition which is likely to change.

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