5.9 Pressure
9 exam questions worth 25 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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What is the unit of pressure?
Choose one answer.
Correct Not quite: the answer is Pascal
Mark scheme
B: Pascal
Model answer
Pascal (B). 1 Pa = 1 N/m².
A force of 200 N acts on an area of 0.50 m². Calculate the pressure.
Mark scheme
p = F / A = 200 ÷ 0.50 (1); 400 Pa (1)
Model answer
p = F / A = 200 / 0.50 = 400 Pa.
A person has a weight of 700 N. The area of the soles of both shoes in contact with the ground is 0.035 m². Calculate the pressure on the ground.
Mark scheme
p = F / A (1); 700 ÷ 0.035 (1); 20 000 Pa (1)
Model answer
p = F / A = 700 / 0.035 = 20 000 Pa.
A pressure of 50 kPa acts on a window of area 0.20 m². Calculate the force on the window.
Mark scheme
50 kPa = 50 000 Pa (1); F = p A = 50 000 × 0.20 (1); 10 000 N (1)
Model answer
50 kPa = 50 000 Pa. F = p A = 50 000 × 0.20 = 10 000 N.
A box has a weight of 60 N. Its base is 20 cm by 30 cm. Calculate the pressure of the box on the table. Give your answer in pascals.
Mark scheme
area = 20 × 30 = 600 cm² (1); = 0.060 m² (1); p = 60 ÷ 0.060 (1); 1000 Pa (1)
Model answer
Area = 20 × 30 = 600 cm² = 0.060 m². p = F / A = 60 / 0.060 = 1000 Pa.
Explain why a drawing pin is easier to push into a notice board with the point down.
Mark scheme
the point has a very small area (1); so the same force gives a much larger pressure (1)
Model answer
The point has a very small area, so the force from your thumb gives a very high pressure at the tip.
Explain why a tractor has wide tyres.
Mark scheme
the weight is spread over a larger area (1); so the pressure on the ground is smaller and the tractor does not sink in (1)
Model answer
Wide tyres spread the weight over a larger area, so the pressure on the soft ground is lower and the tractor does not sink.
Use the particle model to explain why a gas in a sealed container exerts a force on the walls, and state the direction of that force.
Mark scheme
gas particles collide with the walls (1); each collision exerts a force (1); the force acts at right angles to the wall / surface (1)
Model answer
The particles collide with the walls, and each collision exerts a force on the wall. The total force acts at right angles to the surface.
A woman weighing 600 N stands on one stiletto heel of area 1.0 cm². She then wears snow shoes with a total area of 2000 cm² and stands on both. Compare the pressures and explain why the pressures are different.
Mark scheme
heel: 1.0 cm² = 0.00010 m² (1); p = 600 ÷ 0.00010 = 6 000 000 Pa (1); snow shoes: 2000 cm² = 0.20 m² and p = 600 ÷ 0.20 = 3000 Pa (1); pressure is much bigger for the heel (1); same force acts on a much smaller area / pressure = force ÷ area (1)
Model answer
On the heel: p = 600 / 0.00010 = 6 000 000 Pa. On the snow shoes: p = 600 / 0.20 = 3000 Pa. The pressure from the heel is 2000 times bigger because the same force acts on a much smaller area.
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