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Edexcel GCSE Physics

Forces, motion and Newton's laws — Edexcel GCSE Physics revision

Free revision notes, key terms, common exam traps and 5 practice questions with answers. About 5 minutes to read.

Newton's laws

  • 1st: with no resultant force, an object stays still or keeps moving at constant velocity.
  • 2nd: F = m × a — resultant force equals mass times acceleration.
  • 3rd: every action has an equal and opposite reaction on a different object.

Motion and stopping

  • Speed = distance ÷ time. Acceleration = change in velocity ÷ time.
  • Stopping distance = thinking distance + braking distance.
  • Thinking distance rises with speed, tiredness, alcohol and distractions; braking distance rises with speed, wet roads and worn brakes.

Key terms

Resultant force
The single force that has the same effect as all forces combined.
Terminal velocity
Constant speed reached when drag equals weight.
Scalar
A quantity with size only, unlike a vector which also has direction.
Thinking distance
Distance travelled during a driver's reaction time before braking starts.
Braking distance
Distance travelled while the vehicle is decelerating under braking.
Inertia
The tendency of an object to resist changes in its motion.

Common exam traps

  • Confusing mass (kg, constant) with weight (N, depends on gravity).
  • Saying an object at constant velocity has no forces — it has no resultant force.
  • Forgetting thinking distance when asked about stopping distance.

Practice questions with answers

  1. 1. A 1500 kg car accelerates at 2 m/s². Calculate the resultant force.

    Answer: 3000 N

    F = ma = 1500 × 2.

  2. 2. A skydiver reaches terminal velocity. This means:

    • • There is no force acting
    • • Weight equals drag, so resultant force is zero
    • • Weight is greater than drag
    • • They are accelerating

    Answer: Weight equals drag, so resultant force is zero

    Balanced forces mean constant velocity.

  3. 3. State two factors that increase thinking distance.

    Answer: Higher speed and reduced reaction time (tiredness, alcohol or distractions).

    Thinking distance is about the driver, braking distance about the car and road.

  4. 4. Which is a vector quantity?

    • • Speed
    • • Mass
    • • Velocity
    • • Energy

    Answer: Velocity

    Velocity has both size and direction.

  5. 5. What is a scalar quantity?

    • • Has magnitude and direction
    • • Has magnitude only
    • • Only exists in circuits
    • • Always measured in newtons

    Answer: Has magnitude only

    Scalars (e.g. speed, mass) have size but no direction, unlike vectors.

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