TOPIC 1 - Moments and center of gravity: See experiment notes for light beam experiment and explanations (1.33P)

Definition of a moment

A moment is the turning affect of a force - it is the force multiplied by the perpendicular distance from pivot.

Equation linking the moment of a force and its perpendicular distance from pivot

moment = force x perpendicular distance from pivot
(F1 x d1)

What is the effect of increasing the perpendicular distance from pivot?

We can make devices that require less force in order to provide the same turning effect.

Explain the principle of moments
'use the principle of moments for a simple system of parallel forces acting in one plane'

If an object is balanced the sum of the clockwise moment about a pivot will equal the sum of the anti - clockwise moment about that pivot.
(F1 x d1 = F2 x d2)

Definition of the Center of Gravity

The Center of Gravity is the point on an object where its weight acts.

The weight of a body:

Acts through its center of gravity.

The lower the center of gravity:

The more stable the object is.

The wider the base of the object:

The more stable it is.

Define how an object is stable

A body is stable if its center of gravity remains vertically above the base.