physics turning effect of forces chapter 5

Moments

The moment of a force, or torque, about a pivot is defined as the product of the force and and perpendicular distance from the pivot to the direction of the force.

Principle of moments

The principle of moments states that when a body is in equilibrium, the sum of clockwise moments about a pivot is equal to the sum of anti-clockwise moments about the same pivot

C.G

The centre of gravity of an object is defined as an imaginary point where the entire weight of the object seems to act from.

When an object falls to the side:

When x is (verb/displaced) to the left/right, the line of action of its weight passes through the right/left side of the pivot.

The weight creates a clockwise/anti-clockwise moment about the pivot, causes x to turn clockwise/anti-clockwise.

When an object remains upright/does move:

When...,the line of action of its weight passes through the centre of the pivot.

As the perpendicular distance between the weight and the pivot is 0, the moments caused by the weight is 0. Hence it remains upright.

Stability

The stability of the object is a measure of the object's ability to return to its original position.

Affected by:

base area (wide as possible)

centre of gravity (as low as possible)

where is the c.g. of a freely suspended object located?

below the pivot