# Moments.

## Presentation on theme: "Moments."— Presentation transcript:

Moments

Core Describe the moment of a force as a measure of its turning effect and give everyday examples describe, qualitatively, the balancing of a beam about a pivot.

Turning forces Two masses on a see-saw. What force acts on the masses?
Which way will the see-saw go? gravity pivot gravity The see-saw turns around the pivot. What factors effect the size of a turning force?

Moments The size of the turning force or moment depends upon:
The distance of the force from the pivot. The size of the force. Moment = Force x perpendicular distance from pivot Moments measured in Newton metres (Nm) Force measured in Newtons (N) Distance measured in metres (m)

Anticlockwise moments = Clockwise moments
Principle of moments Anticlockwise moments = Clockwise moments 2 m 1 m 25N 50N Where should a force of 50N be positioned to balance the see-saw? Anti-clockwise moments = 25 N x 2 m = 50 Nm Anti-clockwise moments = Clockwise moments 50 Nm = 50 N x ? M distance = 1 m Clockwise moments = 50 N x ? m

Principle of moments Drag and drop any of the masses onto the “see – saw” and try to get it to balance. The masses are in kilograms and the distance in metres. This is a FLASH animation. Please drag and drop the masses onto the ‘see-saw’.

Moments questions Where should a force of 60N be positioned to balance the ruler below? What size force should be positioned on the left to balance the ruler shown? 4 m 1 m 15N 60N 1 m 4 m Force = 60 N ? N 15N

Beams What if the pivot is not in the middle of the ruler?
The ruler´s weight causes another moment at the centre of mass.

Supplement Perform and describe an experiment (involving vertical forces) to verify that there is no net moment on a body in equilibrium. Apply the idea of opposing moments to simple systems in equilibrium.