1. 28/02/2019
Dog-nap

2. Unscramble the note left at the scene of the crime
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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. 28/02/2019
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
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Pivot
Effort
Load

5. A force acting on an object can cause it to turn about a pivot.
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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. The turning effect of a force is called a moment.
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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
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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
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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
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2. Increase the force applied - push/pull harder or get someone stronger to do it!
pivot
Distance from force to pivot
Force

10. F x d Moment The moment of a force is given by the relationship:
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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
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Gina weighs 500 N and stands on one end of a seesaw. She is 0.5 m from the pivot.
What moment does she exert?
moment = 500 x 0.5
= 250 Nm
0.5 m
500 N
pivot

12. Moments F x d moment Calculate the following turning moments: 5 metres
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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
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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
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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
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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
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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