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Turning Forces and Centre of Gravity

Turning Forces and Centre of Gravity. Chapter 42. What is a turning force?. Need 2 volunteers : 1 male 1 female. Turning Forces.

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Turning Forces and Centre of Gravity

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  1. Turning Forces and Centre of Gravity Chapter 42

  2. What is a turning force? Need 2 volunteers : 1 male 1 female

  3. Turning Forces A turning force is something that would allow us to apply a much greater force than pulling or pushing an object like moving a rock It makes use of something called a lever A lever is a rigid body which is free to turn about a fixed point called the fulcrum

  4. Turning Forces The Fulcrum is the part about which the lever turns The effort is where the force is applied The load is where the force takes effect

  5. Everyday examples

  6. Moments The turning effect of the force is called the moment of the force and it depends on 2 things: • The size of the force (measured in Newton's) • The distance (in meters) from the fulcrum to where the force is applied

  7. Some Math… Moment = Force x Distance from the Fulcrum

  8. Balancing Moments If the moments are equal on both sides of the see saw it is balanced

  9. Some Examples A metre stick is suspended from its centre of gravity which is at its midpoint. A force of 3 N acts on the stick at the 90 cm mark and a force of F newtons acts on the stick at the 20 cm mark. Calculate force F.

  10. The Law of The Lever When a lever is balanced, the clockwise and anti-clockwise moments are equal

  11. The Experiment You will need : • A meter stick • Retort stand • Weights • Table to record results * 100g = 1N

  12. Table

  13. Method • Hang the meter stick from the retort stand at the 50cm mark or until it is balanced • Hang a 1N weight on the RHS and a 2N weight on the LHS so they balance eachother • Note the distances of each weight from the fulcrum and calculate the moment • Repeat placing the weights in different positions or adding more weight

  14. Just for fun Try and find the weight of an unknown object… How do you think we can do this? *Phetannimation

  15. Homework Q3, 4 Page 286 In your pairs bring in a piece of cardboard for next week!

  16. Centre of GravityPage 281

  17. Challenges! Volunteers Please

  18. Centre of Gravity The center of gravity of an object is the point through which all the weight of the object appears to act

  19. Investigation to find the centre of gravity of Irregularly Shaped Cardboard Apparatus: • Cardboard • Retort Stand • Cork • Pin • Weight • String • Pencil • Ruler

  20. Equilibrium and The Stability of Objects An object that is balanced and not moving is said to be in equilibrium. There are three states of equilibrium : stable, unstable and neutral An object can be made more stable by: • giving it a low centre of gravity • giving it a wider base An object will topple if a vertical line through its centre of gravity falls outside its base.

  21. States of Equilibrium

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