Levers

Distance from the fulcrum (moment)

You may have noticed when using a first order lever that little effort is needed to move the load if you are further away from the fulcrum than the load. In fact the further you are the less effort is needed. A famous philosopher once said "Give me a lever long enough and I will move the world". You may have played on the see-saw and tried to lift, using your hands, a person on the other side. It is very difficult. If the person comes and sits closer to the fulcrum your work is made easy.

 

The mechanical advantage gained by a lever can be explained by the principle of moments. A moment is the turning effect generated when a force(effort) is applied to a lever to rotate it about the fulcrum.
The moment depends upon the size of the force and its distance from the fulcrum according to the expression below
moment = force X distance
Note that a small force a long distance from the fulcrum can produce a significant moment.

Why do you think this bolt cutter has long handles?

Click to see a 450kb movie of the bolt cutter in action.