Pressure, moments and workIB MYP Sciences: Subtopic test

1. 1
   A camel in the Arabian desert has a weight of 6000 N. Each of its four wide feet has a contact area of 0.075 m² with the sand.

   (a)

   What is the pressure that the camel exerts on the sand when it stands on all four feet?

   [1 mark]

   • A80 000 Pa
   • B20 000 Pa
   • C450 Pa
   • D1500 Pa

   (b)

   Which change would reduce the pressure that the camel exerts on the sand?

   [1 mark]

   • ACarrying a heavy load
   • BLifting one foot off the ground
   • CSpreading its weight over a larger area
   • DStanding on its toes

   (c)

   A tourist weighing 750 N stands on the sand on both feet. The total contact area is 0.050 m². Calculate the pressure that the tourist exerts on the sand.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Amara and Ben sit on a see-saw, which is a uniform plank balanced on a pivot at its centre. Amara weighs 400 N and sits 1.5 m from the pivot. Ben weighs 500 N.

   (a)

   What is the moment of Amara's weight about the pivot?

   [1 mark]

   • A267 N m
   • B401.5 N m
   • C0.0038 N m
   • D600 N m

   (b)

   Ben sits on the other side and the see-saw balances. How far is Ben from the pivot?

   [1 mark]

   • A1.2 m
   • B1.9 m
   • C0.83 m
   • D1.5 m

   (c)

   Ben now moves to 1.5 m from the pivot. Explain what happens to the see-saw.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Sana, a student in Colombo, investigates the principle of moments using a uniform metre rule balanced on a pivot at its 50 cm mark. She hangs a 2.0 N weight 20 cm to the left of the pivot. She then hangs different weights on the right and slides each one along the rule until the rule balances horizontally. The balancing distances from the pivot are 40 cm for 1.0 N, 21 cm for 2.0 N, 10 cm for 4.0 N and 8 cm for 5.0 N.

   (a)

   Describe how Sana should carry out the investigation so that her results are valid, including one safety precaution.

   [3 marks]

   (b)

   Process the data: calculate the moment of the weight on the left and the moment of the 4.0 N weight on the right, state whether the results support the principle of moments, and suggest one reason why the 2.0 N result on the right gives a slightly different moment.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A building site in Lagos uses a hand-operated pulley system to lift materials to the upper floors. A worker pulls the rope with a force of 500 N through a distance of 24 m to raise a 1800 N load by 6.0 m. A diesel-powered crane is the alternative.

   (a)

   Discuss the social, economic and environmental implications of using a hand-operated pulley system rather than a diesel-powered crane.

   [6 marks]

   (b)

   Calculate the work done by the worker and the work done on the load. Explain why the worker does more work than is done on the load.

   [6 marks]

   Total for question 4: 12 marks

End of questions