Page 134 - Science Coursebook

9.7 The turning effect of a force

The photograph shows how to nut spanner
use a spanner to turn a nut. The
mechanic pushes on the long
arm of the spanner.
The force of the mechanic on
the spanner causes it to turn. We
say that the force has a turning

effect. To tighten the nut, the
mechanic must turn it clockwise.
Turning a nut using a spanner.

Opening a door
It takes two forces, each with a turning effect, to open a door. First, you press down on

the door handle. Then the handle turns and you can pull the door open.
The downward force of your hand on the handle makes the handle turn. The handle

doesn’t move straight down. This is because the handle is fixed to the door. The point

where it is fixed is called the pivot.
Similarly, the door has hinges. When you pull on the handle, the door turns about the
hinges. The hinges are the pivot about which the door turns.

pivot
pivot

Opening a door – the forces cause the handle and the door to turn on their pivots.

Question
1 Look at the photograph of the spanner at the top of the page. Draw a
diagram of the spanner and nut, viewed from above. Mark the pivot, and add
an arrow to show the mechanic’s pushing force.

132 9 Forces in action