Question

A door is 1 m wide. It can be closed by an effort of 25 N, when effort is applied at a distance of 0.4 m from the hinge. What effort is needed, if it is applied at its extreme end?

Answer 1

Using the principle of moments about the hinge:

Effort × effort arm = constant.

Let the required effort at the extreme end be E. The extreme end is 1 m from the hinge, so

E × 1 = 25 × 0.4

∴ E = 10 N

Therefore, the required effort is 10 N.