# AQA Unit 2 Physics chapter 7

Depends how much i can do in an hour but im starting to make revision cards for unit 2.

## Vectors and Scalars

Vector - Any physical quantity that has a diretion as well as a magnitude e.g force

Scalar- Any physical quantity that is not directional

Displacement- distance given in a direction

Velocity - speed given in direction

Force and acceleration - both vectors

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## The principles of moments

Turning effects

The moment of a force = Fxd  (nm)

The moment of a force about any point is defined as the force x the perpendiular distance from the line of action of the force to the point

The principle of moments

sum of clockwise moments = sum of anticlockwise moments

Centre of mass

The COM of a body is the point through whih a single fore on the body has no turing effect

The COM will be directly above the point of support

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## More on moments

Single support problems

S = w1 + w2 + w0 (w0 = weight of the rule)

w1d1 = w2d2 because the forces must be balances to support the object

2 support problems

If COM is midway between supports the support force is half the weight of the object on each beam

If its not midway take moments about where both supports are in contact with the beam (e.g)

About X - Sy = Wdx/D

About Y - Sx = Wdy/D

Sy and Sx are the 2 pont where the weight is supported

W is the weight of the object overall

dx and dy are the distances from the support to the centre of mass

D is how far the 2 supports are apart

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