Classes III levers have mechanical advantage less than 1. Why are they then used?

State the class of levers and the relative positions of load (L), effort (E) and fulcrum (F) in

(a) a bottle opener, and

(b) sugar tongs.

Derive a relationship between mechanical advantage, velocity ratio and efficiency of a machine.

Explain why scissors for cutting cloth may have blades longer than the handles, but shears for cutting metals have short blades and long handles.