3.2.15

Moments

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Moments

The turning effect of force around a pivot or fulcrum is called a moment. The moment depends on two factors.

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Moments

  • The turning effect of a force around a pivot or fulcrum is called the ‘moment’.
  • The size of the moment depends on two factors:
    • The amount of force applied. The greater the force the greater the moment.
    • The distance from the pivot/fulcrum to where the force has been applied.
  • So a mechanic will find it easier to undo a wheel nut if he or she uses more force and/or uses a longer spanner.
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Moments on a seesaw

  • On a seesaw, the moment may act in a clockwise or anticlockwise direction.
  • If nobody was on the seesaw, there would be no force acting on it. So it would be level and the moments would be equal and balanced.
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Moment on a seesaw 2

  • For a balanced seesaw:
    • Total clockwise moment = total anticlockwise moment.
  • If somebody got on the righthand side of the seesaw, the seesaw would move in the clockwise direction as the moments would be unbalanced.
  • If somebody got on the lefthand side of the seesaw, the seesaw would move in the opposite direction.
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Calculating moments

  • The unit of a moment is Newton metre (Nm).
  • Moment (Nm) = force (N) x perpendicular distance from the force to the pivot (m).
  • Perpendicular means a straight line from the pivot to the force.
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Moments - customs question

  • If a customs official opens a wooden crate with a 1.5m crowbar by applying a force of 30N, what is the turning effect?
    • Moment = 1.5 x 30 = 45Nm.

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1Biology

1.1Cells, Tissues & Organs

1.2Reproduction & Variation

1.3Ecological Relationships & Classification

1.4Digestion & Nutrition

1.5Plants & Photosynthesis

1.6Biological Systems & Processes

2Chemistry

2.1Particles

2.2Chemical Reactions

2.3Atoms, Elements, Compounds

2.4The Periodic Table

2.5Materials & the Earth

2.6Reactivity

2.7Energetics

2.8Properties of Materials

3Physics

3.1Energy

3.2Forces & Motion

3.3Waves

3.4Electricity & Magnetism

3.5Matter

3.6Space Physics

4Thinking Scientifically

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