# Moments

summary and example question and awnser on moments m1

- Created by: Olivia
- Created on: 08-06-11 14:55

First 194 words of the document:

Moments

Moments are force x distance about a particular point

the units are Nm (Newton metres)

They either act in a clockwise or anti-clockwise direction.

Since moments are vectors one of these directions should be taken as positive.

If an object is said to be in equilibrium then two conditions must apply: the

sum of the moments about any given point must be zero. In other words, the

clockwise and anticlockwise moments will cancel each other out.

The sum of the forces acting on the object must be zero. In moments questions this

usually means the upwards forces cancel out the Downwards forces.

Sketch diagram showing all forces and distances

If the plank is resting on supports there will be a vertical reaction upwards at this

point.

If the plank is uniform then the weight of the plank will act at its midpoint.

Take moments about a point , putting clockwise moments equal to anticlockwise

moments

The line of action through the chosen point its force will be 0 so unknowns can be

removed from the equation.

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