Archimedes (c. 287-c. 212 B.C.E.) had first described the lever in 260 B.C.E. While conducting his research on levers, he stated, “Give me a firm spot on which to stand, and I will move the Earth.” Archimedes was referring to the use of levers; theoretically, with a long enough lever and a non-Earthbound place to rest a fulcrum, one could move the Earth. Which class of lever would you use?

The screwdriver is one example The larger the diameter of the handle the greater the torque that can be applied to the screw. Many examples have a rope or chain wrapped around the axle. A sailing ship’s steering wheel could be represented by either the left-hand or the center drawing, depending on whether the helmsman pushed down or pulled up on the edge of the wheel. The rope around the axle is connected to the rudder, which is then turned to the right or left.

A similar device would be a device to lift a bucket from a well. The wheel is then replaced by a crank, but the operation of the device is exactly the same. Again, the crank can either be pulled up or pushed down to exert a force on the rope to pull the bucket up.

The rear wheel of a bicycle can be thought of as two wheels on an axle. The large wheel has a rubber tire and exerts a backward force on the road while the smaller wheel is the sprocket that the chain turns. The right-hand drawing above shows that the force of the chain is larger than the wheel’s force on the road.