Question

Mechanics sometimes put a length of pipe over the handle of a wrench when trying to remove a very tight bolt. How does this help? (It is also hazardous since it can break the bolt.)

Short answer

The mechanics attach an extra length of pipe over the handle of the wrench, to increase the torque on the bolt.

Step-by-step solution

Rotational motion

The rotational motion depends on the torque and the torque depends on the applied force and the perpendicular distance between the point of application of the force and the point of rotation.

The wrench torque

The torque for the wrench shown in the diagram is,

$\tau =rF\sin \theta$

Here, $\theta$is the angle between the force and the radius of rotation.

Explanation

If the length of pipe attached to the end of the wrench, the effective length that is the radius of rotation increases. Thus the same magnitude of force can provide a larger torque.

Hence, the mechanics attach an extra length of pipe over the handle of the wrench, to increase the torque on the bolt.