Pressure

29 Grade 8 Integrated Science questions on Pressure, with worked marking schemes. 29 questions are available on this topic in full.

1. Question 1

   3 marks

   A block of mass 10 kg rests on a table. The block has a base area of 0.5 m².

   (Take g = 10 N/kg)

   Calculate the pressure exerted by the block on the table.

   (3 marks)

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2. Question 2

   4 marks

   A rectangular block has a weight of 60 N and a base measuring 2 m by 3 m resting on the ground.

   (a) Calculate the area of the base in contact with the ground. (1 mark)

   (b) Calculate the pressure the block exerts on the ground. (3 marks)

   (4 marks)

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3. Question 3

   1 mark

   A tractor used on a soft farm in Kitale is fitted with wide tyres. The wide tyres are used mainly to:

   A. Increase the weight of the tractor

   B. Reduce the force exerted by the tractor

   C. Increase the area of contact so as to reduce pressure on the soft ground

   D. Reduce the area of contact so as to increase pressure

   (1 mark)

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4. Question 4

   1 mark

   A camel walking in a desert has broad, flat feet. The broad feet help the camel to:

   A. Increase pressure so it grips the sand

   B. Reduce pressure on the sand so that it does not sink

   C. Increase its weight on the sand

   D. Move faster on the sand

   (1 mark)

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5. Question 5

   1 mark

   Pressure is defined as

   A. energy per unit time

   B. mass per unit volume

   C. force per unit area

   D. force times area

   (1 mark)

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6. Question 6

   1 mark

   Atmospheric pressure is the pressure exerted by

   A. the sun's heat

   B. the weight of air in the atmosphere

   C. rocks on the ground

   D. water in the oceans

   (1 mark)

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7. Question 7

   1 mark

   A force of 200 N acts on an area of 4 m2. What is the pressure exerted?

   A. 800 Pa

   B. 50 Pa

   C. 0.02 Pa

   D. 204 Pa

   (1 mark)

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8. Question 8

   1 mark

   The SI unit of pressure is

   A. Newton (N)

   B. Joule (J)

   C. Watt (W)

   D. Pascal (Pa)

   (1 mark)

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9. Question 9

   1 mark

   A sharp knife cuts better than a blunt one because

   A. it exerts less pressure

   B. it has more mass

   C. it exerts more pressure on a smaller area

   D. it is made of better material

   (1 mark)

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10. Question 10

    1 mark

    The SI unit of pressure is the:

    A. Newton (N)

    B. Pascal (Pa)

    C. Kilogram (kg)

    D. Joule (J)

    (1 mark)

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11. Question 11

    1 mark

    Which of the following demonstrates the application of high pressure?

    A. A flat-bottomed boat

    B. A camel's wide feet

    C. A snowshoe with a wide base

    D. A nail with a pointed tip

    (1 mark)

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12. Question 12

    4 marks

    A learner pokes several holes at different heights along the side of a tall tin filled with water.

    (a) State what the learner will observe about the water jets from the holes.

    (b) Explain the observation in terms of pressure.

    (4 marks)

    Marking scheme

    (a) The water from the lowest hole comes out with the greatest force and travels the furthest; water from the higher holes comes out with less force and travels a shorter distance (2). (b) This is because pressure in a liquid increases with depth, so the water at the bottom is under the greatest pressure and is pushed out with the greatest force (2).

13. Question 13

    4 marks

    (a) Define pressure and state its SI unit. (2 marks)

    (b) Explain why a sharp knife cuts more easily than a blunt one. (2 marks)

    (4 marks)

    Marking scheme

    (a) Pressure is the force acting normally (perpendicularly) per unit area. Its SI unit is the pascal (Pa) or newton per square metre (N/m^2). (b) A sharp knife has a very small surface area at its edge. Since pressure is inversely proportional to area, the same force applied over the smaller area of the sharp edge produces a much greater pressure, so it cuts more easily than a blunt knife which has a larger edge area and therefore exerts less pressure.

14. Question 14

    4 marks

    (a) Explain why a sharp knife cuts more easily than a blunt knife when the same force is applied. (2 marks)

    (b) State TWO ways in which the pressure exerted by a solid on a surface can be reduced. (2 marks)

    (4 marks)

    Marking scheme

    (a) A sharp knife has a smaller surface area (thinner edge) than a blunt knife. Since pressure is force divided by area, applying the same force over the smaller area of the sharp knife produces a greater pressure, so it cuts more easily. (2 marks) (b) Any TWO of: increasing the area of contact over which the force acts; reducing the force/weight acting on the surface. (1 mark each)

15. Question 15

    1 mark

    As altitude increases, atmospheric pressure

    A. doubles

    B. decreases

    C. increases

    D. stays the same

    (1 mark)

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16. Question 16

    1 mark

    Wide tyres are used on tractors to

    A. increase the pressure on the ground

    B. reduce the pressure on soft ground

    C. make the tractor faster

    D. reduce fuel consumption

    (1 mark)

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17. Question 17

    1 mark

    In a liquid, pressure at a given point acts:

    A. Only downwards

    B. Only sideways

    C. Only upwards

    D. In all directions

    (1 mark)

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18. Question 18

    4 marks

    A box exerts a force of 200 N on the ground through an area of 0.5 m^2.

    (a) Calculate the pressure exerted by the box on the ground. (3 marks)

    (b) State what happens to the pressure if the same box is placed on a smaller area. (1 mark)

    (4 marks)

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19. Question 19

    4 marks

    (a) Explain why a sharp knife cuts more easily than a blunt one, using the idea of pressure. (2 marks)

    (b) Explain why the walls of a dam are made thicker at the bottom than at the top. (2 marks)

    (4 marks)

    Marking scheme

    (a) A sharp knife has a very small (thin) edge area in contact with the object. Since pressure = force / area, applying the same force over a smaller area produces a much greater pressure, so it cuts more easily than a blunt knife which has a larger edge area and therefore exerts less pressure. (b) Pressure in a liquid increases with depth. The water at the bottom of the dam exerts a greater pressure than the water near the top, so the walls are made thicker at the bottom to withstand the higher pressure and prevent the dam from breaking.

20. Question 20

    4 marks

    (a) State two factors that affect the pressure exerted by a solid on a surface.

    (b) Explain why a person wearing high-heeled shoes is more likely to damage a soft floor than one wearing flat shoes.

    (4 marks)

    Marking scheme

    (a) The force/weight applied (1) and the area of contact (1). (b) The high heel has a very small area of contact with the floor, so for the same weight the pressure exerted is very high (concentrated on a small area), and this high pressure sinks into or damages the soft floor (2).

21. Question 21

    4 marks

    Explain why:

    (a) A camel can walk easily on sand.

    (b) A drawing pin has a sharp point.

    (4 marks)

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22. Question 22

    4 marks

    Liquid pressure increases with depth.

    (a) Explain how the design of a dam wall makes use of this fact.

    (b) Give one everyday Kenyan example, other than a dam, where this fact is applied.

    (4 marks)

    Marking scheme

    (a) The pressure of the water is greatest at the bottom of the dam, so the wall is made thicker/stronger at the base to withstand the greater pressure and prevent it from bursting (2). (b) Any one valid example (2): a raised water storage tank on a high stand delivers water at higher pressure to taps below; a water tank is made stronger at its base; deep boreholes/pipes are made stronger lower down. Total 4 marks.

23. Question 23

    1 mark

    If a force of 100 N is applied over an area of 2 m², the pressure exerted is

    A. 200 Pa

    B. 102 Pa

    C. 50 Pa

    D. 100 Pa

    (1 mark)

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24. Question 24

    1 mark

    Why is it easier to cut vegetables with a sharp knife than a blunt one?

    A. A sharp knife has a smaller area so it exerts greater pressure

    B. A blunt knife has a smaller area and more pressure

    C. A sharp knife applies a greater force automatically

    D. A sharp knife reduces the force needed to zero

    (1 mark)

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25. Question 25

    4 marks

    (a) State two factors that affect the pressure exerted by a solid on a surface. (2 marks)

    (b) Explain why a tractor used in muddy fields is fitted with wide tyres. (2 marks)

    (4 marks)

    Marking scheme

    (a) The force (weight) applied; and the area of contact over which the force acts. (b) Wide tyres have a large area of contact with the ground. Since pressure = force / area, increasing the area of contact reduces the pressure exerted on the soft/muddy ground, so the tractor does not sink into the mud.

26. Question 26

    4 marks

    A rectangular block of weight 60 N rests on a table. The block has a base measuring 0.5 m by 0.4 m.

    (a) Calculate the area of the base in contact with the table. (1 mark)

    (b) Calculate the pressure exerted by the block on the table. (3 marks)

    (4 marks)

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27. Question 27

    1 mark

    A dam wall is built thicker at the bottom than at the top. This is because pressure in a liquid:

    A. Is the same at all depths

    B. Acts only at the surface

    C. Increases with depth

    D. Decreases with depth

    (1 mark)

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28. Question 28

    3 marks

    A box weighing 600 N rests on the ground. The area of contact between the box and the ground is 3 m2.

    (a) Calculate the pressure exerted by the box on the ground.

    (b) State the SI unit of pressure.

    (3 marks)

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29. Question 29

    1 mark

    Pressure is defined as:

    A. Force acting per unit area

    B. Force multiplied by distance

    C. Mass per unit volume

    D. Force multiplied by area

    (1 mark)

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