Chapter 8, Problem 85A

To determine

The reason that during static equilibrium, axis of rotation is usually placed at a point where maximum forces are acting.

Answer to Problem 85A

To reduce the calculations because the torque due to these forces will be zero at the axis of rotation.

Explanation of Solution

Introduction:

The torque is given by,

  $\tau =Fr\sin \theta$

Where, F is the applied force, r is the distance of the point of application of force from the axis of rotation, and $\theta$ is the angle between F and r .

If the axis of rotation is placed at the point of application of maximum forces, then considering the above formula, the value of $r$ for these forces and thereby the torque due to these forces will be zero.

Conclusion:

By considering the axis of rotation at the point of application of maximum forces, one can nullify the torque generated by these forces on the system.