Pressure in solidsIB MYP Physics: Subtopic test

1. 1
   A warehouse worker in Rotterdam rests a wooden crate that weighs 900 N on a concrete floor. The largest face of the crate has an area of 1.5 m² and its smallest face has an area of 0.50 m².

   (a)

   Which unit is equivalent to the pascal (Pa)?

   [1 mark]

   • AN/m²
   • BN m
   • CN/m
   • Dkg m/s

   (b)

   What pressure does the crate exert on the floor when it rests on its largest face?

   [1 mark]

   • A1350 Pa
   • B1800 Pa
   • C600 Pa
   • D0.0017 Pa

   (c)

   Calculate the pressure when the crate rests on its smallest face. Explain why this pressure is different from the pressure on its largest face.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A skier in the Swiss Alps weighs 700 N. Each ski has a contact area of 0.20 m². Without skis, her two boots have a total contact area of 0.04 m². The snow is deep and soft.

   (a)

   Why does the skier sink less in the soft snow when she wears skis?

   [1 mark]

   • AThe skis reduce her weight, so the force on the snow is smaller
   • BThe skis spread her weight over a larger area, so the pressure is smaller
   • CThe skis reduce the contact area, so the pressure is smaller
   • DThe skis increase the pressure, so the snow becomes firmer

   (b)

   What pressure do her boots exert on the snow when she stands without skis?

   [1 mark]

   • A28 Pa
   • B3500 Pa
   • C175 000 Pa
   • D17 500 Pa

   (c)

   Calculate the pressure the skier exerts on the snow when she stands on both skis.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Students investigate how the area of contact affects the pressure on soft sand. A brick of weight 24 N is placed on a tray of sand, resting on a different face each time. The three faces have areas of 0.020 m², 0.010 m² and 0.005 m². The depth of the dent in the sand was 3 mm, 6 mm and 12 mm respectively.

   (a)

   State a testable hypothesis for this investigation and give a scientific reason for it. State the dependent variable.

   [3 marks]

   (b)

   Calculate the pressure for each face. Describe the pattern between pressure and depth, say whether the results support your hypothesis, and suggest one improvement.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A farming cooperative in Punjab is choosing between two types of tyre for a tractor that weighs 60 000 N. Standard tyres have a total contact area of 1.2 m² with the soil. Wide tyres have a total contact area of 2.4 m², but they cost more and cannot fit between the narrow rows of some crops. The soil is often wet and soft after the monsoon.

   (a)

   Calculate the pressure that the tractor exerts on the soil with each type of tyre. Explain why the wide tyres are better on wet, soft soil.

   [6 marks]

   (b)

   Discuss and evaluate whether the cooperative should buy tractors with wide tyres.

   [6 marks]

   Total for question 4: 12 marks

End of questions