Torque
A rotational force, also known as a torque, depends upon the force and where that force is applied;
The lever arm or moment arm is the perpendicular distance from the force to the axis of rotation.
Consider the torque exerted on this wrench by a force applied in different directions or in different places.
We can also write this as
= torque = r F sin
where r is the distance between the pivot point and where the force F is applied.
or
= F d where
d = moment arm the perpendicular distance from the pivot point to the line of action of the force F,
And, since
sin = sin (180o - ) That is, the angle can be either of the angles between position vector r and the force F.
= r F sin
Moment of Inertia Newton's Second Law Return to ToC, Ch10, Rotation about a Fixed Axis (c) Doug Davis, 2001; all rights reserved