IGCSE Physics 1.5 Forces MCQs – 30 Practice Questions with Answers (Cambridge 0625)

Free practice questions for Cambridge IGCSE Physics (0625) Section 1.5, Forces, covering resultant force and Newton’s laws, springs and moments, and vectors and circular motion. Every question is original, with the correct answer and worked explanation hidden behind the Show Answer button so you can test yourself first.

Formula Recap

Need the equations first? Revise resultant force (F = ma), Hooke’s law (F = kx) and moment = force × perpendicular distance on the IGCSE Physics Formula Sheet, then come back and try these questions.

Resultant Force & Newton’s Laws

Q1. A book rests on a table. The weight of the book and the normal reaction from the table are equal and opposite. What is the resultant force on the book, and what happens to it?

  • (A) 5 N downwards; it accelerates downwards
  • (B) 5 N upwards; it rises slowly
  • (C) Zero; it stays at rest
  • (D) Zero; it moves at constant speed
Show Answer

Answer: C – The two forces are balanced, so the resultant force is zero. An object with zero resultant force stays at rest if it was already at rest (Newton’s first law).

Q2. A box is pushed to the right with a force of 12 N. Friction acts to the left with a force of 5 N. What is the resultant force on the box?

  • (A) 17 N to the right
  • (B) 7 N to the right
  • (C) 7 N to the left
  • (D) 17 N to the left
Show Answer

Answer: B – Forces in opposite directions subtract: 12 N − 5 N = 7 N, in the direction of the larger force, so 7 N to the right.

Q3. A resultant force acts on an object of mass 4.0 kg and gives it an acceleration of 3.0 m/s2. What is the size of the resultant force?

  • (A) 12 N
  • (B) 1.3 N
  • (C) 7.0 N
  • (D) 0.75 N
Show Answer

Answer: A – F = ma = 4.0 × 3.0 = 12 N.

Q4. A resultant force of 20 N acts on a trolley of mass 5.0 kg. What is the acceleration of the trolley?

  • (A) 0.25 m/s2
  • (B) 100 m/s2
  • (C) 15 m/s2
  • (D) 4.0 m/s2
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Answer: D – a = F / m = 20 / 5.0 = 4.0 m/s2.

Q5. A bus brakes suddenly and the passengers are thrown forwards. Which statement best explains this?

  • (A) A forward force pushes the passengers when the brakes are applied
  • (B) The passengers tend to keep moving forwards at constant speed because the resultant force on them is (almost) zero
  • (C) The passengers’ weight increases when the bus slows down
  • (D) Friction between the passengers and the seats acts forwards
Show Answer

Answer: B – By Newton’s first law, the passengers keep their existing motion when the bus slows down, so they continue moving forwards relative to the bus.

Q6. A car travels along a straight, flat road at a constant speed. The engine provides a driving force of 800 N. What can be said about the total resistive force (friction and air resistance) and the resultant force?

  • (A) Resistive force is zero and resultant force is 800 N
  • (B) Resistive force is greater than 800 N and the car is slowing down
  • (C) Resistive force is 800 N and resultant force is zero
  • (D) Resistive force is less than 800 N and resultant force is 800 N
Show Answer

Answer: C – Constant speed means the acceleration is zero, so the resultant force is zero: the resistive force must exactly balance the 800 N driving force.

Q7. The resultant force on a moving object is zero. What happens to the motion of the object?

  • (A) It continues moving at a constant velocity
  • (B) It gradually slows down and stops
  • (C) It speeds up at a steady rate
  • (D) It immediately stops
Show Answer

Answer: A – With zero resultant force there is no acceleration, so the velocity stays constant (Newton’s first law). This is why a puck sliding on frictionless ice keeps moving.

Q8. A crate is pulled across the floor to the right and slides at a steady speed. In which direction does the friction force on the crate act, and why?

  • (A) To the right, because friction helps the motion
  • (B) Downwards, because friction is caused by weight
  • (C) Upwards, because friction reduces the normal reaction
  • (D) To the left, because friction always opposes the direction of motion
Show Answer

Answer: D – Friction (and air resistance) always act opposite to the direction of motion, so here friction acts to the left.

Q9. A resultant force of 30 N gives an object an acceleration of 6.0 m/s2. What is the mass of the object?

  • (A) 180 kg
  • (B) 5.0 kg
  • (C) 0.20 kg
  • (D) 36 kg
Show Answer

Answer: B – m = F / a = 30 / 6.0 = 5.0 kg.

Q10. Two forces of 8 N and 6 N act in the same direction on an object of mass 2.0 kg. What is the acceleration of the object?

  • (A) 1.0 m/s2
  • (B) 3.0 m/s2
  • (C) 7.0 m/s2
  • (D) 14 m/s2
Show Answer

Answer: C – Forces in the same direction add: resultant force = 8 + 6 = 14 N. Then a = F / m = 14 / 2.0 = 7.0 m/s2.

Springs, Moments & Turning Effects

Q11. A spring has a spring constant k = 20 N/m. A force of 6.0 N is applied to it, within its limit of proportionality. What is its extension?

  • (A) 3.3 m
  • (B) 0.30 m
  • (C) 120 m
  • (D) 0.03 m
Show Answer

Answer: B – Hooke’s law: F = kx, so x = F / k = 6.0 / 20 = 0.30 m.

Q12. An unstretched spring is 12 cm long. Its spring constant is 50 N/m. A load of 10 N is hung from it. What is the new length of the spring?

  • (A) 14 cm
  • (B) 22 cm
  • (C) 20 cm
  • (D) 32 cm
Show Answer

Answer: D – Extension x = F / k = 10 / 50 = 0.20 m = 20 cm. New length = 12 + 20 = 32 cm.

Q13. On a graph of force against extension for a spring, the line is straight at first and then begins to curve. What does the point where the line starts to curve represent?

  • (A) The limit of proportionality, beyond which extension is no longer proportional to force
  • (B) The point where the spring suddenly breaks
  • (C) The spring constant changing to zero
  • (D) The maximum force the spring can measure
Show Answer

Answer: A – Up to the limit of proportionality the graph is a straight line through the origin (Hooke’s law). Beyond that point the spring no longer obeys F = kx.

Q14. A force of 40 N is applied at a perpendicular distance of 0.25 m from a pivot. What is the moment of the force about the pivot?

  • (A) 160 N m
  • (B) 1.6 N m
  • (C) 10 N m
  • (D) 40 N m
Show Answer

Answer: C – Moment = force × perpendicular distance from the pivot = 40 × 0.25 = 10 N m.

Q15. A beam is balanced on a pivot. A 30 N weight hangs 0.40 m to the left of the pivot. An unknown weight hangs 0.60 m to the right of the pivot and the beam balances. What is the unknown weight?

  • (A) 45 N
  • (B) 20 N
  • (C) 30 N
  • (D) 12 N
Show Answer

Answer: B – Principle of moments: clockwise moment = anticlockwise moment. 30 × 0.40 = F × 0.60, so F = 12 / 0.60 = 20 N.

Q16. Which design makes an object most stable (least likely to topple over)?

  • (A) A wide base and a low centre of mass
  • (B) A narrow base and a high centre of mass
  • (C) A wide base and a high centre of mass
  • (D) A narrow base and a low centre of mass
Show Answer

Answer: A – A wide base and a low centre of mass mean the line of action of the weight stays inside the base even when the object is tilted a long way, so it is very stable.

Q17. A door handle is placed as far from the hinges as possible. Why does this make the door easier to open?

  • (A) It increases the force applied to the door
  • (B) It reduces the friction at the hinges
  • (C) It reduces the mass of the door
  • (D) It increases the moment of the applied force about the hinge (pivot)
Show Answer

Answer: D – Moment = force × perpendicular distance from the pivot. A larger distance gives a larger turning effect for the same push.

Q18. A force of 8.0 N stretches a spring by 0.040 m, within the limit of proportionality. What is the spring constant?

  • (A) 0.32 N/m
  • (B) 20 N/m
  • (C) 200 N/m
  • (D) 0.005 N/m
Show Answer

Answer: C – k = F / x = 8.0 / 0.040 = 200 N/m.

Q19. The total clockwise moments about a pivot are 15 N m and the total anticlockwise moments are also 15 N m. What happens to the object?

  • (A) It rotates clockwise
  • (B) It is balanced and does not rotate
  • (C) It rotates anticlockwise
  • (D) It moves in a straight line
Show Answer

Answer: B – By the principle of moments, an object in equilibrium has total clockwise moments equal to total anticlockwise moments, so there is no resultant turning effect.

Q20. A spanner is used to turn a nut. The same force is applied, but the length of the spanner is doubled. What happens to the moment?

  • (A) It doubles
  • (B) It halves
  • (C) It stays the same
  • (D) It becomes four times larger
Show Answer

Answer: A – Moment = F × d. With F unchanged, doubling the perpendicular distance d doubles the moment.


Vectors, Friction & Circular Motion [partly Supplement]

Q21. Which quantity is a vector?

  • (A) Speed
  • (B) Distance
  • (C) Mass
  • (D) Velocity
Show Answer

Answer: D – A vector has both magnitude and direction. Velocity is a vector; speed, distance and mass are scalars (magnitude only).

Q22. Which quantity is a scalar?

  • (A) Force
  • (B) Acceleration
  • (C) Energy
  • (D) Momentum
Show Answer

Answer: C – Energy has magnitude only, so it is a scalar. Force, acceleration and momentum all have direction as well, so they are vectors.

Q23. A force of 9 N acts to the east and a force of 4 N acts to the west on the same object. What is the resultant force?

  • (A) 13 N to the east
  • (B) 5 N to the east
  • (C) 5 N to the west
  • (D) 13 N to the west
Show Answer

Answer: B – Vectors along the same line are added with direction taken into account: 9 N east − 4 N west = 5 N to the east.

Q24. In which situation is friction useful?

  • (A) Grip between a car’s tyres and the road so the car can move and brake
  • (B) Friction in the moving parts of an engine
  • (C) Air resistance slowing a falling parachutist’s supply crate with no parachute
  • (D) Friction between a sledge and snow that must be overcome to start it moving
Show Answer

Answer: A – Without friction between the tyres and the road, the wheels would spin and the car could not accelerate, steer or brake. Friction in engines is usually unwanted because it wastes energy as heat.

Q25. Which method reduces friction between two solid surfaces?

  • (A) Making the surfaces rougher
  • (B) Pressing the surfaces together harder
  • (C) Adding a lubricant such as oil between the surfaces
  • (D) Increasing the area of the surfaces in contact
Show Answer

Answer: C – A lubricant separates the surfaces with a thin layer of liquid, which greatly reduces the friction between them.

Q26. [Supplement] An object moves in a circle at a constant speed. In which direction does the resultant (centripetal) force on it act?

  • (A) Along the tangent, in the direction of motion
  • (B) Towards the centre of the circle
  • (C) Away from the centre of the circle
  • (D) There is no resultant force because the speed is constant
Show Answer

Answer: B – Circular motion needs a centripetal force directed towards the centre of the circle, at right angles to the velocity, which keeps changing the direction of motion.

Q27. [Supplement] A satellite orbits the Earth in a circular path at constant speed. What provides the centripetal force?

  • (A) The satellite’s engines
  • (B) Air resistance
  • (C) The satellite’s own thrust forwards
  • (D) The gravitational attraction of the Earth
Show Answer

Answer: D – Gravity pulls the satellite towards the centre of the Earth, providing the centripetal force that keeps it in orbit.

Q28. [Supplement] A car drives around a circular bend at constant speed on a flat road. What provides the centripetal force?

  • (A) Friction between the tyres and the road
  • (B) The engine’s driving force
  • (C) The normal reaction from the road
  • (D) The weight of the car
Show Answer

Answer: A – On a flat road the sideways friction between the tyres and the road acts towards the centre of the bend and provides the centripetal force. This is why bends are dangerous on ice, where friction is small.

Q29. [Supplement] An object moves in a circle at a constant speed. Why is it accelerating even though its speed does not change?

  • (A) Its mass is changing
  • (B) Its kinetic energy is increasing
  • (C) Its velocity is changing because its direction of motion keeps changing
  • (D) It is not accelerating
Show Answer

Answer: C – Velocity is a vector, so a change of direction is a change of velocity. A changing velocity means an acceleration, which is provided by the centripetal force towards the centre.

Q30. Two forces of 3 N and 4 N act at right angles to each other at the same point. Using the parallelogram of forces (or Pythagoras), what is the magnitude of the resultant force?

  • (A) 7 N
  • (B) 1 N
  • (C) 12 N
  • (D) 5 N
Show Answer

Answer: D – The two forces form two sides of a right-angled triangle: resultant = √(32 + 42) = √(9 + 16) = √25 = 5 N. On a scale diagram the diagonal of the parallelogram (here a rectangle) gives the same resultant.

Keep Revising Physics

Work through more boards and topics on the Physics MCQs hub, and keep every 0625 equation in one place with the IGCSE Physics Formula Sheet.

All questions on this page are original practice questions written for QuaidianPoint. They are not Cambridge past-paper questions.