Identifying lengths and distances on the lever

Length and distance

Thinking about the teaching

If I apply a force to the end of a lever there are two measurements, both in metres, which I might pay attention to in describing the event:

• The length, L₁, from the pivot to the line of action of the force
• The distance, D₁, that the force moves as the lever pivots

Teacher Tip: Keep the lengths (L₁, L₂) from the pivot to the line of action of the forces separate from the distances moved by those forces as the lever spins (D₁, D₂).

This will help you think about either moments or energy.

To analyse the action of the lever in terms of moments:

• You'll need to consider the size of the force acting and the length from the line of action of the force to the pivot (L₁).

To analyse the action of the lever in terms of energy:

• You'll need to consider the size of the force acting and the distance moved by that force (D₁).