The jaws of this shark are put in motion by a trigger at the bottom of the stick (there's a rope inside which transmits this motion). The trigger is pretty long, but the shark's teeth close strongly, especially the incisor teeth.

This is how a lever works, allowing us to work by applying less force.

If we want to move the glass-wipers all over the car windscreen, we just have to move a short lever on the other extremity, but a pretty powerful engine has to do it.

Shark lever is an example in which the motion of the trigger is transmitted to the jaws by a piece of string.

If we want to lift a heavy stone, we place it at the shorter end of a rigid beam, whereas the opposite end of the beam plots a much longer curve downwards. For example, in order to lift 100 kg piece of rock by 5 cm the weight of 10 kg at the opposite end has to lowered by 50 cm. The product of the force and the distance moved by its point of application along the line of action of force, i.e. work at both ends is equal.

In a different kind of lever - one-side lever, in which one of the ends is also its pivot, the turning moment is the greatest.

Levers have had numerous applications - from the old fashioned analytical balance, or scales at Berlin underground station to a hydraulic jack.