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Dog-nap

Dog-nap. Unscramble the note left at the scene of the crime. ‘ YOU NOT BY JERRY HAVE SEE IF ME YOUR SPRINGER NEVER WILL DOG £9,999 TOMORROW GIVE I DO AGAIN YOU ’. Levers. Levers are simple machines. They can make work easier by increasing the size of a force.

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Dog-nap

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  1. Dog-nap

  2. Unscramble the note left at the scene of the crime ‘ YOU NOT BY JERRY HAVE SEE IF ME YOUR SPRINGER NEVER WILL DOG £9,999 TOMORROW GIVE I DO AGAIN YOU ’

  3. Levers Levers are simple machines. They can make work easier by increasing the size of a force. Forces can move objects by turning them around a point, we call this a pivot. A seesaw is a lever, when you push down on one side you are applying an effort, and the person on the other side (the load) moves up. Label the diagram

  4. Levers Pivot Effort Load

  5. pivot 5N A force acting on an object can cause it to turn about a pivot. What would happen to the see-saw above ? Would it turn? If so, clockwise or anti-clockwise?

  6. pivot The left goes down - an anticlockwise turn. The turning effect of a force is called a moment. We use many simple levers in the home Write down three examples of levers

  7. Moments Pivot Distance from force to pivot Force Suppose you were trying to unscrew a nut using a spanner. The spanner exerts a moment or turning force on the nut. If the moment is big enough it will unscrew the nut. If not there are 2 ways of increasing the moment.

  8. Increasing the moment 1. Increase the distance from the force to the pivot - apply the force at the end or use a longer spanner. Pivot Distance from force to pivot Force

  9. Increasing the moment 2. Increase the force applied - push/pull harder or get someone stronger to do it! pivot Distance from force to pivot Force

  10. Moment The moment of a force is given by the relationship: Moment = Force (N) x Distance (cm or m). Moments are measured in Newton centimetre (Ncm) or Newton metre (Nm). moment F x d

  11. Moments calculation Gina weighs 500N and stands on one end of a seesaw. She is 0.5m from the pivot. What moment does she exert? moment = 500 x 0.5 = 250 Nm 0.5m 500N pivot

  12. Moments moment Calculate the following turning moments: F x d 5 metres 100 Newtons 2 metres 200 Newtons

  13. Objects found near the scene of the crime Crowbar 40cm Letter opener 17cm Spanner 29cm Screwdriver 24cm

  14. Results Crowbar 40cm x 80N = 3200N/cm Letter opener 17cm x 80N = 1360N/cm Spanner 29cm x 80N = 2320N/cm Screwdriver 24cm x 80N = 1920N/cm Therefore only the crow bar and spanner could have been used to lever open the window

  15. Further results Force = Moment ÷ Distance Letter opener 2000N/cm ÷ 17cm = 118N Screwdriver 2000N/cm ÷ 24cm = 83N

  16. Further results When you double the force applied… Letter opener 17cm x 160N = 2720N/cm Screw driver 24cm x 160N = 3840N/cm Therefore the letter opener and screw driver may have been used if there were two people applying force

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