Forces and Pressure Important Questions

8th Standard EM

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Science

Time : 01:30:00 Hrs
Total Marks : 60
    5 x 1 = 5
  1. If we apply a force against the direction of motion of a body, then the body will

    (a)

    stop moving

    (b)

    move with an increased speed

    (c)

    move with a decreased speed

    (d)

    move in a different direction

  2. The unit of viscosity is

    (a)

    N m2

    (b)

    poise

    (c)

    kg m s–1

    (d)

    no unit

  3. _______is the force acting perpendicularly on any given surface area of a body

    (a)

    Pressure

    (b)

    Thrust

    (c)

    Density

    (d)

    Volume

  4. The unit for surface tension is _________

    (a)

    Nm

    (b)

    N-1m

    (c)

    N-1m-1

    (d)

    Nm-1

  5. If the area of contact is greater, then the ______ will be greater.

    (a)

    Pressure

    (b)

    Temperature

    (c)

    Friction

    (d)

    Force

  6. 5 x 1 = 5
  7. The pressure of a liquid column _____ with the depth of the column.

    ()

    Increases

  8. The property of _____ of a liquid surface enables the water droplets to move upward in plants.

    ()

    surface tension

  9. Liquids and gases together are called as___________

    ()

    Fluids

  10. _________decides whether an object will sink or float

    ()

    Upward force

  11. _______causes wear and tear of the surfaces in contact

    ()

    Friction

  12. 4 x 1 = 4
  13. Force acting on a given area is called pressure.

    (a) True
    (b) False
  14. A body will sink if the weight of the body is greater than the buoyant force.

    (a) True
    (b) False
  15. Friction is called as necessary evil

    (a) True
    (b) False
  16. A knot in a thread is an example of kinetic friction

    (a) True
    (b) False
  17. 5 x 1 = 5
  18. Static friction

  19. (1)

    objects are at rest

  20. Rolling friction

  21. (2)

    Kg m-1S-1

  22. Lubricants

  23. (3)

    reduce friction

  24. Force

  25. (4)

    Kg ms-2

  26. Viscous force

  27. (5)

    objects are sliding

    3 x 2 = 6
  28. Assertion: Sharp knives are used to cut the vegetables.
    Reason: Sharp edges exert more pressure.
    a. If both assertion and reason are true and the reason is the correct explanation of the assertion.
    b. If both assertion and reason are true, but the reason is not the correct explanation of the assertion.
    c. If the assertion is true, but the reason is false.
    d. If the assertion is false, but the reason is true.

  29. Assertion: Water strider slides easily on the surface of water.
    Reason: Water strider experiences less buoyant force.
    a. If both assertion and reason are true and the reason is the correct explanation of the assertion.
    b. If both assertion and reason are true, but the reason is not the correct explanation of the assertion.
    c. If the assertion is true, but the reason is false.
    d. If the assertion is false, but the reason is true.

  30. Assertion (A): Football shoes are having soles with many projections
    Reason (R): Provides stronger grip with the ground
    a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
    b) If both assertion and reason are true but reason is not the correct explanation of the assertion.
    c) If the assertion is true but the reason is false.
    d) If the assertion is false, but the reason is true.

  31. 2 x 2 = 4
  32. Knot in a thread : _____ friction; ball bearing : _____ friction

  33. Treaded tyres : Increase friction
    ___________ : Decrease friciton

  34. 6 x 2 = 12
  35. A stone weighs 500 N. Calculate the pressure exerted by it if it makes a contact with a surface of area 25 cm2.

  36. Give two examples to verify that a force tends to change the static condition of a body.

  37. Name two instruments, which help to measure the pressure of a fluid.

  38. Define one atmosphere.

  39. Why sumo and kabbadi players rub their hand with mud?

  40. What makes the peel of banana to slide over the path?

  41. 3 x 3 = 9
  42. Define friction. Give two examples of the utility of friction in day to day life.

  43. Write down three ways of minimising friction.

  44. A bubble rises from the bottom of a pond to its surface by increasing its radius by 3 times its value when it was at the bottom. Calculate the depth of the pond. (Hint: Pressure depends on the depth of the pond. Volume is inversely related to pressure.) [Science Olympiad]

  45. 2 x 5 = 10
  46. “Friction is a necessary evil”- explain.

  47. Explain Manometer with the diagram

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