Unit F - Moments (copy)

1c (1.30-1.33)

Equation: Moment, Force, Perp distance from pivot

Equation: Moment, Force, Perp distance from pivot

M = Fd

Moment = Force x perpendicular Distance from pivot

[Nm] = [N] x [m]

Centre of graivty

The point at which the weight of an object acts

A freely suspended object swings until centre of gravity is vertically below point of suspension

Finding centre of gravity

• Suspend shape and a plumb line from same point, and wait until they stop moving

• Draw line along plumb line

• Repeat but suspend shape from different pivot point

• Centre of gravity is where two lines cross

Principle of moments

If object is balanced:

Total Anticlockwise moments = Total Clockwise moments

Upwards forces with heavy object on light beam

• If a light rod (no weight) is being supported at both ends, upwards force provided by each support isn’t always the same

• If heavy object is placed on rod, support closest to object provides larger force