# AQA Unit 2 Physics chapter 7

7.5 onwards

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## Stability

If a body in a stable equilibruim is released, it returns to its equilibruim position . This is because the Centre of mass of the objet is directly below the support at rest

Tilting and Toppling

Short, wide based objects will be harder to topple

Tilting

for tilting to occur Fd > wb/2

b is the width of the base

W is the weight of the object

F is the force applied

d is the perpendicular distance from the line of action of F to the pivot

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## Toppling

If an object is tilted so the line of action of its weight passes beyond the pivot.

On a slope for e.g

Parrallel - F= Wsintheta

Perpendicular - Sx + Sy = Wcostheta

This is basically the use of pythag

This can be used by drawing a triangle using the slope as one edge and a perpendicular edge as another. Theta is given by the angle between these 2 lines

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## Equilibrium Rules

Free Body Force Diagrams

Show only the forces acting on the object

When 2 objects interact they always exert equal opposite forces on eachother

The Triangle of forces

An object acted on by 3 forces have a resultant of 0

Can be drawn in a vector triangle here is where its best to use Pythag

Conditions For an equilibrium

• Resultant Force must be 0 (3 forces must form a closed triangle)
• Principle of moments must apply ( moments of the forces about the same point must balance out
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## Comments

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7.5 - 7.6 i missed out statics calculations as they cant really be reduced to revision cards and the overall ideas are explained through the chapters.

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