Question

Why wrench or spanner has long handle?

Answer 1

A force applied by a wrench can rotate a nut or can open a door, while the door rotates on its hinges. In addition to the tendency to move a body in the direction of the application of a force, a force also tends to rotate the body about any axis which does not intersect the line of action of the force and also not parallel to it. This tendency of rotation is called the turning effect of a force or moment of the force about the given axis. The magnitude of the moment of force about a point is de ned as the product of the magnitude of force and the perpendicular distance of the point from the line of action of the force.
Then, the moment of force = force x perpendicular distance
Moment of force = F x d.

Answer 2

Torque is the product of length r and the force F. We apply force at the end of the spanner thus longer handle implies more r implying more torque for same force.