2CoreDescribe the moment of a force as a measure of its turning effect and give everyday examplesdescribe, qualitatively, the balancing of a beam about a pivot.
3Turning forces Two masses on a see-saw. What force acts on the masses? Which way will the see-saw go?gravitypivotgravityThe see-saw turns around the pivot.What factors effect the size of a turning force?
4Moments 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 pivotMoments measured in Newton metres (Nm)Force measured in Newtons (N)Distance measured in metres (m)
5Anticlockwise moments = Clockwise moments Principle of momentsAnticlockwise moments = Clockwise moments2 m1 m25N50NWhere should a force of 50N be positioned to balance the see-saw?Anti-clockwise moments = 25 N x 2 m= 50 NmAnti-clockwise moments = Clockwise moments50 Nm = 50 N x ? Mdistance = 1 mClockwise moments = 50 N x ? m
6Principle of momentsDrag 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’.
7Moments questionsWhere 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 m1 m15N60N1 m4 mForce = 60 N? N15N
8Beams What if the pivot is not in the middle of the ruler? The ruler´s weight causes another moment at the centre of mass.
9SupplementPerform 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.