Objective 5.4

5.4 Starter

07 October 2011

11:46
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5.4 Starter 2 explained

07 October 2011

09:04

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· Your finger pushes on the pin and the pin pushes back on your finger
· N3L tells us that all these two forces are equal in size
· The pin pushes on the wall and the wall pushes back on the pin
· N3L tells us that all these two forces are also equal in size
· If the surface area is large then the force is spread over a large area and the pressure is low
· If the surface area is small then the force is spread over a small area and the pressure is high
· You would like the pressure on your finger to be low and the pressure on the wall to be high
· The other way round is painful!

5.4

07 October 2011

10:37
· 5.4 recall and use the relationship between pressure, force and area:

pressure = force / area

p = F / A

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animation - why a drawing pin works.swf Download this file