1. MOMENT OF A FORCE
• If a force F is acting on a body resting at 0 and the line of action of
force does not pass through G, the centre of gravity of the body, it
will not give the body a straight line motion, called the translator
motion. But will try to rotate the body about 0 as shown in Figure.
The measure of this property of a force by virtue of which it tends
to rotate body on which it acts is called the moment of a force, The
rotation of the body may be either about a point or a line.

2. MOMENT OF A FORCE
Here, point 0 is known as moment centre or fulcrum and
distance x is termed as moment arm.
∴ Moment of Force = Force x perpendicular distance between the line
of action of the force and the point or the axis
about which moment is required
If the moment of the about a point is zero, it means either the force
itself is zero or the perpendicular distance between the line of action
of the force and the point about which moment is to be calculated is
zero i.e. the force passes through that point.

3. MOMENT OF COPLANAR FORCES

4. MOMENT OF COPLANAR FORCES
 Example:

5. Solution,
MOMENT OF COPLANAR FORCES

6. The moment of a force F with respect to a point A is defined as a vector with
a magnitude equal to the product of the perpendicular distance from A to F
and the magnitude of the force and with a direction perpendicular to the
plane containing A and F.
The sense of the moment vector is given by the direction a right-hand screw
would advance if turned about A in the direction indicated by F as shown in
Figure.
MOMENT OF A FORCE ABOUT A POINT AND AN AXIS

7. The moment of a force about a line or axis perpendicular to a plane
containing the force is defined as a vector with a magnitude equal to the
product of the magnitude of the force and the perpendicular distance from
the line to the force and with a direction along the line.
Thus, it is the same as the moment of the force about the point of
intersection of the plane and the moment axis.
Since the moment of a force about an axis is a measure of its tendency to
turn or rotate a body about the axis, the force parallel to an axis has no
moment with respect to the axis, because it has no tendency to rotate the
body about the axis.
MOMENT OF A FORCE ABOUT A POINT AND AN AXIS