The lever principle is that the two moments (the product of the force and the moment arm) acting on the lever must be equal in size.

That is: power × power arm = resistance × resistance arm, expressed in algebra as F1·L1=F2·L2.

In the formula, F1 represents power, L1 represents power arm, F2 represents resistance, and L2 represents resistance arm.

Therefore, to make the lever reach equilibrium, the power arm is several times the resistance arm, and the resistance is several times the power.

When using a lever, in order to save effort, you should use a lever with a power arm that is longer than the resistance arm; if you want to save distance, you should use a lever with a power arm that is shorter than the resistance arm.

Therefore, using leverage can save effort and distance.

However, if you want to save effort, you must move more distance; if you want to move less and invade the mutual distance, you must expend more effort.