5.4 Moments, Levers & Gears

What may cause an object to rotate?

A force or a system of forces.

What are three real-world examples of forces causing rotation?

• Turning a spanner

• Opening a door

• Using a see-saw

What is the moment of the force?

The turning effect of a force.

What is the pivot?

The point around which the object can rotate.

What is the line of action?

A straight line that a force acts along.

What is the equation for the moment of the force?

M = Fd

What is the moment of the force measured in?

newton-metres (Nm)

If an object is balanced, the total _____________ moment about a pivot equals the total ____________ moment about that pivot.

• clockwise

• anticlockwise

We measure the distance from the _______ to the ______ __ ________ of the force.

When we measure the distance we must always measure it ______________ (at right angles) to the line of action of the force.

This is the _____________ distance from the pivot to the line of action.

• pivot

• line of action

• perpendicular

• shortest

What can a simple lever and a simple gear system be used to do?

To transmit the rotational effects of forces.

Levers (and gears) can be used to increase the __________ by allowing us to apply the ________ further from the pivot.

This means _______ force is needed to get the same _________.

For this reason, levers and gears are examples of _________ __________ — a small effort force can be __________ and result in a much larger force acting on the load.

• moment

• force

• less

• moment

• force multipliers

• multiplied

If a gear is supplying the force (first gear) and its connected to a gear with fewer teeth, what happens to the second gear?

• It turns faster

• with less force

• in the opposite direction

If a gear is supplying the force (first gear) and its connected to a gear with more teeth, what happens to the second gear?

• It turns slower

• with more force

• in the opposite direction

With two gears, the forces that act on the teeth are ______.

As the left gear turns its teeth exert an _____ force on the teeth of the right gear.

Despite the forces being _____ they are different ________ from their axles, which means the moments are ________.

• equal

• equal

• equal

• distances

• different