Turning Effect Of Forces

Question 1

Moment of forces, M

Answer 1

Product of the perpendicular distance from the pivot to the line of action of the force and the force. (SI unit: Nm)
M=Fd

Question 2

Couple

Answer 2

Two equal and opposite parallel forces whose lines of action do not coincide

Question 3

Principle of moments

Answer 3

When a body is in equilibrium, the sum of clockwise moments about a pivot is equals to the sum of anti-clockwise moments about the same pivot

Question 4

Centre of gravity

Answer 4

The point at which the entire weight of an object appears to act, for any orientation of the object

Question 5

Stable equilibrium

Answer 5

The line of action of the weight lies within the base area of the object, hence there is a restoring moment causing the object to return to its original position

Question 6

Unstable equilibrium

Answer 6

The line of action of the weight lies outside of the base area of the object, hence there is an overturning moment to tilt the object further in the same direction