Mechanics - Statics - AQA A-Level Physics

Scalar

A quantity containing only magnitude

Vector

A quantity containing direction and magnitude

Equilibrium

At rest or at constant velocity

Triangle of forces

A method used to determine if the point acted on by 3 forces is in equilibrium, by checking the forces give an overall resultant of zero and form a triangle

Newton’s first law

An object will remain at constant velocity unless acted on by a resultant force

Newton’s second law

The rate of change of velocity (acceleration) of an object is directly proportional to the applied force and inversely proportional to its mass

Moment

The turning effect of a force around a pivot

The principle of moments

sum of clockwise moments = sum of anticlockwise moments

Couple

Two forces which are equal in magnitude but anti-parallel

What is one factor that the torque of a couple does not depend on?

The position of the pivot

Features of a stable structure

• A low centre of mass

• A broad base

Tilting

A force causes an object to be raised on one side, causing a moment about a pivot point

When will an object topple?

When the line of action of the weight passes beyond the pivot