Chapter 11, Problem 2A

In what direction should a force be applied to produce maximum torque?

To determine

The direction in which the force must be applied to produce a maximum torque.

Answer to Problem 2A

In perpendicular direction of the lever arm.

Explanation of Solution

Introduction:

The torque acting about an axis of rotation due to the force $F$ is given by,

  $\begin{array}{c}\tau =F\times \left(\text{lever arm}\right)\\ =F\left(\text{lever arm}\right)\sin \theta \end{array}$

Where,

  $\text{lever arm=}$ denotes the shortest distance of the point of application of force from the axis of rotation.

  $\theta =$ angle between the force and the lever arm

Now, as can be seen from above, if the angle between the force and the lever arm is $90°$ , then the produced torque will be maximum.

Conclusion:

Hence, the force must be applied in a perpendicular direction of the lever arm to produce maximum torque.