Levers

Mechanical advantage

By using a lever Jonathon can lift a load of 3000N using an effort of just 300N. We say that the lever has a mechanical advantage.

To calculate just how much mechanical advantage, we use the expression below.

Mechanical advantage = 3000/300
 => 10

Look at the lever system on the right. A load of 30N is supported by a 10N effort. What is its mechanical advantage?

Scan the image for the answer

 
Mechanical advantage is 3.

Stephen pushes down with a force of 60N to just lift the load off the ground. What is the mechanical advantage of the lever?

Scan the image for the answer

Mechanical advantage is 5.

 

Stephen pushes down with a force of 300N to just lift the load off the ground. What is the mechanical advantage of the lever?

Scan the image for the answer

Mechanical advantage is 10

 
Bolt cutters can deliver a staggering force of 20 kilonewtons, that is the equivalent of around 2,040 kilograms. It is even more impressive when you think that this is done by the perosn only applying a force on the handles equivalent to 25 kilograms or 250 kilonewtons.

Look at the animation on the right. Suggest how this magnification of force is achieved.

 
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