Question

It becomes easier to open or close a door turning about its hinges if the force is applied at the:

• A. Two third of the door
• B. Free edge of the door
• C. Middle of the door
• D. Point near the hinges

Answer 1

The correct option is B Free edge of the door

Torque acting about any point O ${\tau }_o=rF$ for $sin\theta =1$

where $r$ is the distance of the application of force from point O.

As $r$ is maximum when a force is applied at the free end of the door, thus less amount of force is required to produce the same torque. Hence it is easier to open or close the door if force is applied at its free end.