South Africa Matric Ā· Physical Sciences

Mechanics: forces, energy and momentum

30 practice questions, each with the answer and an explanation.

Practise Mechanics: forces, energy and momentum now

Random questions from this topic, one at a time. You see the answer and the explanation straight after each one.

All 30 questions

  1. A book rests on a table. Why are the weight of the book and the normal force of the table NOT a Newton's third-law action-reaction pair?
  2. A passenger lurches forward when a moving bus brakes suddenly. Which law or principle best explains this?
  3. A skydiver falling through air reaches terminal velocity when
  4. In which situation is the total linear momentum of a system conserved?
  5. In an elastic collision between two objects,
  6. According to the work-energy theorem, the net work done on an object is equal to
  7. A ball is thrown vertically upwards. At its highest point, the ball's
  8. A resultant force of 4.5 N acts on an object of mass 3 kg. Calculate its acceleration.
  9. A resultant force acts on a 4 kg trolley and gives it an acceleration of 2 mĀ·sā»Ā². Calculate the magnitude of the resultant force.
  10. A resultant force acts on a 2 kg trolley and gives it an acceleration of 2.5 mĀ·sā»Ā². Calculate the magnitude of the resultant force.
  11. A resultant force acts on a 10 kg trolley and gives it an acceleration of 2 mĀ·sā»Ā². Calculate the magnitude of the resultant force.
  12. A resultant force of 36 N acts on an object of mass 12 kg. Calculate its acceleration.
  13. Calculate the weight of a 8 kg object near the Earth's surface (take g = 9,8 mĀ·sā»Ā²).
  14. Calculate the weight of a 5 kg object near the Earth's surface (take g = 9,8 mĀ·sā»Ā²).
  15. Calculate the weight of a 75 kg object near the Earth's surface (take g = 9,8 mĀ·sā»Ā²).
  16. Calculate the momentum of a 3 kg trolley moving at 2 mĀ·sā»Ā¹.
  17. A 2 kg ball hits a wall at 2 mĀ·sā»Ā¹ and rebounds in the opposite direction at 6 mĀ·sā»Ā¹. Calculate the magnitude of the change in momentum of the ball.
  18. Calculate the momentum of a 3 kg trolley moving at 6 mĀ·sā»Ā¹.
  19. A constant net force of 50 N acts on an object for 2 s. Calculate the magnitude of the impulse delivered.
  20. A 4 kg ball hits a wall at 3 mĀ·sā»Ā¹ and rebounds in the opposite direction at 4 mĀ·sā»Ā¹. Calculate the magnitude of the change in momentum of the ball.
  21. A force of 10 N is applied at 60Ā° to the horizontal and moves a crate 5 m along a horizontal floor. Calculate the work done by the force.
  22. An object is dropped from rest from a height. It hits the ground at 20 mĀ·sā»Ā¹. Ignoring air resistance, from what height was it dropped (take g = 9,8 mĀ·sā»Ā²)?
  23. Calculate the kinetic energy of a 50 kg object moving at 4 mĀ·sā»Ā¹.
  24. A force of 20 N is applied at 30Ā° to the horizontal and moves a crate 5 m along a horizontal floor. Calculate the work done by the force.
  25. A force of 30 N is applied at 30Ā° to the horizontal and moves a crate 10 m along a horizontal floor. Calculate the work done by the force.
  26. A force of 20 N is applied at 60Ā° to the horizontal and moves a crate 4 m along a horizontal floor. Calculate the work done by the force.
  27. A car with an initial velocity of 2 mĀ·sā»Ā¹ accelerates uniformly at 5 mĀ·sā»Ā² for 4 s. Calculate the distance it travels in this time.
  28. A car with an initial velocity of 5 mĀ·sā»Ā¹ accelerates uniformly at 2 mĀ·sā»Ā² for 3 s. Calculate the distance it travels in this time.
  29. A car with an initial velocity of 2 mĀ·sā»Ā¹ accelerates uniformly at 5 mĀ·sā»Ā² for 2 s. Calculate the distance it travels in this time.
  30. A car with an initial velocity of 2 mĀ·sā»Ā¹ accelerates uniformly at 5 mĀ·sā»Ā² for 4 s. What is its final velocity?

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