Pressure and depth
4 marks · NormalA scientist designs a rectangular tank filled with oil. The base measures 0.80 m by 1.20 m. The oil has a density of 900 kg/m³. The height of the oil column is 2.0 m and g = 10 N/kg.
Calculate the pressure difference between the top and bottom of the oil in the tank.
Calculate the force exerted by the oil on the base of the tank.
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(a) 18000 Pa · must show substitute h=2.0, ρ=900, g=10, evaluate
(b) 17280 N · must show correct area, force = pressure × area
Common mistakes: Using wrong area or density
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Marking points
M1 (a) · 1 mark · Substitute values into p = hρg
A1 (a) · 1 mark · Correct calculation of 18000 Pa (follow-through)
M2 (b) · 1 mark · Calculate base area (0.96 m²) and use force = pressure × area (follow-through)
A2 (b) · 1 mark · Correct final force (17280 N) (follow-through)
Worked solution
a)
b) Base area = 0.80 × 1.20 = 0.96 m². Force = 18000 × 0.96 = 17280 N.