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

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 [1] [1] [1] [1]

Question 2 – 6 marks Density = m/v = 1kg / 0.001m3 = 1000kg/m3 [1] [1] Density = m/v = 1kg / 0.001m3 = 1000kg/m3 P = ρ g h = 1000 x 10 x 5 = 50 000 N/m2 P = ρ g h = 1000 x 10 x 40 = 400 000 N/m2 or Pa [1] [1] [1] [1 units]

Question 3 – 6 marks W = mg = 80 x 10 = 800 N P = F/A [1] [1] 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. [1] [1] [1] [1]

Question 4 - 7 marks Total CWM = (20x0.5) + (50 x 0.7m) = 10 + 35 [1] [1] Total CWM = (20x0.5) + (50 x 0.7m) = 10 + 35 = 45Nm ΣACWM = ΣCWM 45Nm = Fx 1m F = 45N [1] [1] [1]

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] [1]

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 [1] [1] [1] [1]