4.5.4.0 - Moments , levers and gears

What can cause an object to rotate?

A force or a system of forces may cause an object to rotate

What is the ‘moment’ of the force?

The turning effect of a force is called the moment of the force

Give the equation used to calculate the moment of a force.

moment of force = force x distance

M = Fd

What did distance is referred to in this equation.

The perpendicular distance from the pivot to the line of action of the force

Give the units for all the components in the equation.

Moment - in newton metre , Nm

Force - in newtons, N

Distance - in metres

What can cause a larger moment?

• Larger distance

• Larger force

• (Angle of force applied )

How do you get the maximum moment (turning effect) ?

To get the maximum moment you need to push at a right angle - perpendicular to the ‘handle’

So pushing at any other angle means a smaller distance and so a smaller moment

If the total clockwise moment about a pivot is equal to the total anticlockwise moment about a pivot, the object is….

…. balanced

What can be used to transmit the rotational effects of forces ?

Simple lever

Simple gear system

What do levers make easier?

Levers make it easier to do work

How do levers make it easier to do work?

Levers increase the distance from the pivot at which the force is applied

Since M = Fd , this means less force is needed to get the same moment

Making it easier to do work

What do gears do?

Gears transmit the rotational effects of forces

Describe how gears work.

Gears have teeth that interlock with one another

So that turning one will cause another to turn - in the opposite direction

How can gears be used to change the moment of the force?

Different sized gears can be used to change the moment

Force that is transmitted to a larger gear will cause a greater moment, at the the distance to the pivot is greater

Do larger gears turn slower or faster?

Larger gear will turn slower.