Pressure — Numerical Practice
Covers: p = F/A and the liquid pressure equation Δp = ρgΔh. 14 questions.
A. Pressure as Force per Unit Area
A force of 300 N acts over an area of 0.6 m². Calculate the pressure.
A pressure of 2000 Pa acts over an area of 0.05 m². Calculate the force.
A force of 150 N produces a pressure of 750 Pa. Calculate the area over which it acts.
A block exerts a force of 40 N on the ground. Compare the pressure produced when it rests on a face of area 0.02 m² versus a face of area 0.08 m², and state which produces the greater pressure.
Explain, using p = F/A, why a drawing pin has a sharp point.
Explain, using p = F/A, why snowshoes stop a person sinking into snow.
A woman’s stiletto heel has a contact area of 0.0001 m². If her weight is 600 N, and momentarily all of it rests on one heel, calculate the pressure exerted.
B. Liquid Pressure
Calculate the pressure due to water at a depth of 5 m. (density of water = 1000 kg/m³, g = 9.8 N/kg)
Calculate the depth in water needed to produce a pressure of 19600 Pa. (density of water = 1000 kg/m³, g = 9.8 N/kg)
Calculate the pressure at a depth of 2 m in a liquid of density 800 kg/m³. (g = 9.8 N/kg)
Compare the pressure at 0.5 m depth in water (density 1000 kg/m³) and in mercury (density 13600 kg/m³). (g = 9.8 N/kg)
Explain, in terms of the liquid above a point, why pressure increases with depth in a liquid.
A submarine experiences a pressure of 500000 Pa due to the water above it. Calculate the depth of the submarine. (density of water = 1000 kg/m³, g = 9.8 N/kg)
Explain, using ideas about liquid pressure and depth, why a dam wall is built thicker at the bottom than at the top.
Mastery Test
A force of 500 N acts over an area of 2 m². Calculate the pressure.
A pressure of 800 Pa acts over an area of 0.25 m². Calculate the force.
A force of 90 N produces a pressure of 450 Pa. Calculate the area.
Explain, using p = F/A, why cutting with a blunt knife requires more force than cutting with a sharp knife.
Calculate the pressure due to water at a depth of 8 m. (ρ = 1000 kg/m³, g = 9.8 N/kg)
Calculate the depth in water needed to produce a pressure of 9800 Pa. (ρ = 1000 kg/m³, g = 9.8 N/kg)
Calculate the pressure at a depth of 4 m in a liquid of density 950 kg/m³. (g = 9.8 N/kg)
Explain the effect on pressure of increasing the area over which a force acts, for a constant force.
A force of 1000 N acts once over an area of 0.5 m² and once over 2 m². Calculate the pressure in each case, and state which produces the greater pressure.
Explain, in terms of the liquid above a point, why pressure increases with depth in a liquid.
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