The energy of a body is its capacity (or ability) to do work.

Match the following columns :
Column A Column B
(a) Needle (i) class II lever
(b) Door knob (ii) inclined plane
(c) Ramp (iii) class I lever
(d) Lemon crusher (iv) wheel and axle
(e) See-saw (v) wedge

When is work said to be done by a force ?