1. Year 9 Density, Pressure & Moments Test
Mark Scheme / 30

2. Question 1 – 4 marks W = mg = 60 x 10 = 600N
Pfeet = F/A = 600/(2x180) = 1.67 N/cm2
Pnew shoes = 600/(2x60) = 5 N/cm2
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3. Question 2 – 6 marks Density = m/v = 1kg / 0.001m3 = 1000kg/m3
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Density = m/v = 1kg / 0.001m3 = 1000kg/m3
P = ρ g h = 1000 x 10 x 5 = N/m2
P = ρ g h = 1000 x 10 x 40 = N/m2 or Pa
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4. Question 3 – 6 marks W = mg = 80 x 10 = 800 N P = F/A
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W = mg = 80 x 10 = 800 N
P = F/A
A = 0.01cm2 x 1000 = 10cm2
P = 800/10 = 80N/cm2
Force constant / weight does not change
Area on bed of nails is much larger so pressure is much lower not high enough to pierce skin.
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5. Question 4 - 7 marks Total CWM = (20x0.5) + (50 x 0.7m) = 10 + 35
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Total CWM = (20x0.5) + (50 x 0.7m) =
= 45Nm
ΣACWM = ΣCWM
45Nm = Fx 1m
F = 45N
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6. Question 4 continued
Increasing length of spanner, increases the moment of the force, therefore it is easier to undo the bolt.
Increasing distance of the force from the pivot (hinge) increases the moment of the force therefore easier to open the door. [1]
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7. Question 5 – 7 marks Liquid [1]
Does not compress / transfers pressure [1]
PLHS = F/A = 600/1 =600 N/m2
PRHS = 600 N/m2 [1]
FRHS = P x A = 600 x 5 = 3000N
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