# AQA Physics Unit 3

if you know this youre sorted :)

- Created by: S Satish
- Created on: 21-04-11 16:43

First 409 words of the document:

What is a moment?

The turning effect of a force is called a moment.

How do you increase a moment?

You can increase it by increasing the size of the force or using a greater distance.

If the moment is 35Nm when the perpendicular distance was 10m what is the size of the force applied?

35Nm = force x 10m

Force = 35Nm/10m

Force = 3.5N

What is the centre of mass of an object?

This is the point at which all of its mass may thought to be concentrated.

What happens in a suspended equilibrium?

When a suspended object is in equilibrium then it's centre of mass is directly beneath its point of suspension.

Where is the centre of mass of objects?

For a symmetrical object, the centre of mass will be along its line of symmetry.

How do you find the centre of mass of a flat card?

You suspend it freely from a pin and then use a plumb line to draw a vertical line downwards and then repeat this from a

second point. The centre of mass is where the lines meet.

What is the principle of moments?

The sum of the clockwise moments about any point is equal to the sum of the anticlockwise moments about that same

point for an object in equilibrium.

What is the weight of the second object if two objects are in equilibrium and the first object is 60N with 30m from the

pivot and the second object is 20m from the pivot?

60 x 30 = 180

180/20 = 90N

How is the stability of an object increased?

You can increase the stability of an object by lowering the centre of mass of the object or widening the base.

When will an object tend to topple?

An object will tend to topple when the line of action of its weight is outside its base.

Explain circular motion

For an object that is moving in a circle at a constant speed will be continuously accelerating towards the centre of the circle

and this is because there is always a constant change in velocity which occurs because there is always a constant change in

direction since the object always has to be at a tangent to the circle.

What is a centripetal force?

## Comments

No comments have yet been made