question_answer

Which one is easier to turn-a log or a bench of equal weight and length? The two have the same coefficient of friction with the ground. Explain.

Answer:

                In the case of a log, the force of friction is distributed along its entire length and so it is effective midway between the end where the force is applied and the centre of the log, but in the case of a bench, the force of friction is at the end. So to turn the log, the torque required is equal to\[\text{ }\!\!\mu\!\!\text{  mg }l/2,\], while to turn the bench, the torque required is equal to \[\text{ }\!\!\mu\!\!\text{  mg}\,l\]. Hence it is easier to turn a log than a bench of equal weight and length.