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Moments and Turning Forces. Hold a rod horizontally and hang a weight on the rod near your hand. Have your partner move the weight away from your hand, try to keep the rod horizontal. What happens? Now try it with a heavier weight. What affects the turning force?. distance. Force.
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Hold a rod horizontally and hang a weight on the rod near your hand. Have your partner move the weight away from your hand, try to keep the rod horizontal. What happens? Now try it with a heavier weight. What affects the turning force? distance Force
How is the Turning force or Moment affected by the distance from the pivot? • As the perpendicular distance increases the turning force increases • How is the Turning force affected by the force (effort) exerted? • As the force increases the moment increases
How is the Turning force or Moment affected by the distance from the pivot? • As the perpendicular distance doubles the turning force doubles • How is the Turning force affected by the force (effort) exerted? • As the force doubles the moment doubles • Therefore
Unit for Moment • Determine the unit for Moment of a force. • Newton metre (Nm)
d 10N 20cm 40cm 20N 70N Is Moment a vector quantity? • Does the direction matter?
Calculate the moments below. In which direction are they acting? Clockwise or anticlockwise? Find the total moment acting on the bar above. When more than one force acts in the same direction, their overall turning effect is just the sum of their moments. Moments can either be clockwise or anticlockwise.
Moments Circus • There are six stations. • Using the sheet provided record the effort used on each object and measure the perpendicular distance to the pivot • Finally, calculate the turning force or moment. • Do not forget units!!
When forces act in a different direction, yet still balance, the total turning effect in each direction will be the same: sum of clockwise moments = sum of anticlockwise moments What did you notice about the anticlockwise moment and the clockwise moment? Experiment -Testing the principle of moments
Try This: Copy diagram in books and find force F. F d1=80cm d2=60cm Weight = 30N
Problem 1 - Find force F Mini white board activity with large moments apparatus 0.90m 0.30m F 60N
Problem 2 - Find force F F 10cm 20cm 45N
Problem 3 - Find distance d d 0.60m 20N 30N 44N 0.20m
d 10N 20cm 40cm 20N 70N • Problem 4 - Find distance d