
Moment of a force: It is the product of force and the perpendicular distance (between the line of action of the force and the pivot).
Moment of a force = F x d

Moments can be clockwise or anticlockwise.

The Principle of Moments: For a body in equilibrium, the sum of clockwise moments is equal to the sum of anticlockwise moments.

Example:


Centre of mass: It is the point through which the whole weight of an object seems to act for any orientation of the object.

Centre of mass of an object (such as ring) can lie outside the object.

Experiment to determine centre of mass of a plane lamina

The marking points are:

set metal swinging (to ensure minimal friction at pivot)

allow to come to rest

use of plumb line from hole

mark line along plumb line (on metal)

hang from another hole

hang from 3 rd hole

point of intersection of lines is centre of mass




Stability: It is the ability of an object to regain its original position after it has been tilted slightly.

Stability can be improved by

lowering the centre of mass

increasing the broadness of base


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