Science 8 · Unit 3: Forces and energy · Cambridge Lower Secondary Science Stage 8

Questions

1. 1. What is the equation for pressure?

   • pressure = mass ÷ area
   • pressure = area ÷ force
   • pressure = force × area
   • pressure = force ÷ area
   Check

2. 2. What does a pressure of 20 N/cm² mean?

   • A force of 1 N acts on 20 cm².
   • The area is 20 cm².
   • A force of 20 N acts on each 1 cm² of area.
   • The mass is 20 kg.
   Check

3. 3. Which shoes exert the greatest pressure on the floor?

   • flippers
   • shoes with thin stiletto heels
   • flat trainers
   • wide snow boots
   Check

4. 4. A box has faces of 15 cm², 40 cm² and 60 cm². Which face gives the smallest pressure on the floor?

   • the 60 cm² face
   • the 15 cm² face
   • they are all the same
   • the 40 cm² face
   Check

5. 5. A 15 N book stands on an end of area 60 cm². What pressure does it exert?

   • 0.25 N/cm²
   • 4 N/cm²
   • 900 N/cm²
   • 75 N/cm²
   Check

6. 6. A nail needs 60 N/mm² to enter wood. Its tip is 0.5 mm². What force is needed?

   • 60.5 N
   • 120 N
   • 0.008 N
   • 30 N
   Check

7. 7. Why are rose thorns more likely to injure you than the rest of the stem?

   • They are softer.
   • They have a large area.
   • They are hotter.
   • Their small points give a high pressure.
   Check

8. 8. Why does a board under a car wheel stop it sinking into sand?

   • It heats the sand.
   • It increases the pressure.
   • It makes the car lighter.
   • It spreads the weight over a larger area, reducing the pressure.
   Check

9. 9. Why is a sharp knife better for cutting bread?

   • It has a larger area.
   • It is heavier.
   • It is colder.
   • The thin edge has a small area, so the pressure is high.
   Check

10. 10. Why is one end of a drawing pin wide and flat?

    • to make it sharp
    • to spread the force on your thumb so it doesn't hurt
    • to make it heavier
    • to make it go into the wall
    Check

11. 11. Why is the other end of a drawing pin sharp?

    • to look nice
    • to spread the force
    • to protect your thumb
    • to make a high pressure so it goes into the wall
    Check

12. 12. Why do snowshoes stop you sinking into snow?

    • They increase pressure.
    • They have a large area, reducing pressure.
    • They melt the snow.
    • They make you lighter.
    Check

13. 13. What happens to pressure if the force doubles and the area stays the same?

    • It doubles.
    • It halves.
    • It becomes zero.
    • It stays the same.
    Check

14. 14. What happens to pressure if the area doubles and the force stays the same?

    • It stays the same.
    • It doubles.
    • It halves.
    • It quadruples.
    Check

15. 15. If force is in pounds and area in square inches, what is the unit of pressure?

    • pound inches
    • square inches per pound
    • pounds per square inch
    • pounds per inch
    Check

16. 16. An elephant weighs 50 000 N. Its four feet have a total area of 0.4 m². What pressure does it exert on the ground?

    • 125 000 N/m²
    • 12 500 N/m²
    • 20 000 N/m²
    • 200 000 N/m²
    Check

17. 17. A box weighs 60 N. The area touching the ground is 0.5 m². What pressure does it exert?

    • 12 N/m²
    • 120 N/m²
    • 60.5 N/m²
    • 30 N/m²
    Check

18. 18. A thumb tack has a point of 0.5 mm². It needs 40 N/mm² to go into a wall. What force is needed?

    • 20 N
    • 40.5 N
    • 80 N
    • 0.0125 N
    Check

19. 19. Why does a camel not sink into the sand?

    • Its feet are very hard.
    • It is very light for its size.
    • It walks very fast.
    • Its large feet spread its weight over a large area.
    Check