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MOMENTS

MOMENTS. Noadswood Science, 2013. MOMENTS. To be able to calculate moments. MOMENTS. Forces can make objects turn if there is a pivot Think of a see-saw – when no-one is on it, the see-saw is level, but when someone sits on the end it tips

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MOMENTS

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  1. MOMENTS Noadswood Science, 2013

  2. MOMENTS To be able to calculate moments

  3. MOMENTS • Forces can make objects turn if there is a pivot • Think of a see-saw – when no-one is on it, the see-saw is level, but when someone sits on the end it tips • The see-saw can be balanced again if someone sits on the other end Pivot

  4. MOMENTS • To work out moments we need to know: - • The force (weight) applied • The distance from the pivot where the force is applied Moment (Nm) = Force (N) x Distance (m) Pivot

  5. Distance = perpendicular distance, r MOMENTS • To work out moments we need to know: - • The force (weight) applied • The distance from the pivot where the force is applied Moment (M) Force (F) Distance (D) Force = Moment  DistanceDistance = Moment  Force Moment = Force x Distance

  6. BALANCED • Complete the moments worksheet

  7. MOMENTS • Anticlockwise moment = 600N x 2m = 1200Nm • Clockwise moment = 300N x 2m = 600Nm • Not balanced – anticlockwise moment 600N 300N 2m 2m Anticlockwise moment Clockwise moment

  8. MOMENTS • Anticlockwise moment = 500N x 1m = 500Nm • Clockwise moment = 250N x 2m = 500Nm • Balanced! 500N 250N 1m 2m Anticlockwise moment Clockwise moment

  9. MOMENTS • Anticlockwise moment = 100N x 5m = 500Nm • Clockwise moment = 700N x 3m = 2100Nm • Not balanced – clockwise moment 100N 700N 5m 3m Anticlockwise moment Clockwise moment

  10. MOMENTS • Anticlockwise moment = 300N x 3m = 900Nm • Clockwise moment = 450N x 2.5m = 1125Nm • Not balanced – clockwise moment 300N 450N 3m 2.5m Anticlockwise moment Clockwise moment

  11. BALANCING EXPERIMENT • Balance a ruler on a pivot • Add a mass at the end of the ruler • Your task is to balance the ruler again, by adding 2x masses to the other side • Record the distance where they were placed • Now move your original mass, and repeat the experiment, recording your results

  12. RESULTS Moment (Nm) = Force (N) x Distance (m)

  13. CRANES • Why don’t construction cranes fall over? • Cranes have a concrete counterweight on the short arm, balancing the crane when it lifts a heavy load

  14. trolley load arm counterweight loading platform tower CRANES • Counterweights balance the crane

  15. CRANE OPERATOR

  16. Moments • Complete the moments higher worksheet… • A cross on the point of contact between the screwdriver and the rim of the paint tin (not the end of the screwdriver) • Move his hand further from the tin to increase the distance from the pivot, hence increasing the moment, or apply a bigger force (or both) • 0.10m x 35N = 3.5Nm

  17. Moments • (10N x 2m) + (2N x 0.5m) – (35N x 1m) = -14Nm There will be an anti-clockwise acceleration • See diagram below…

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