Objective 5.4

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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

5.4 Pressure Questions

07 October 2011

11:47

·         PFY p.91, Q.3 and 7.

p=F/A

100,000=F/10

F=1,000,000N 

a) p=F/A

p=500/5

p=100N/cm2

b) p=F/A

100=F/20

F=2,000N

Question 1: Because the snow shoes apply less pressure on the snow because the snow shoes have a large surface area and because the shoes spread the weight, the person using them dosent fall into the snow

Question 2: Because with big tyres there is less pressure on them because the weight of the truck is more evenly spread amongst the tyres and because there is a bigger surface area, the truck does not sink if your driving on e.g. a muddy road

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