Edexcel GCSE Physics Topic 2: Motion and Forces Exam Questions

About Edexcel GCSE Physics Topic 2: Motion and Forces

Topic 2 is one of the biggest topics on Paper 1 of Edexcel GCSE Physics. It starts with scalar and vector quantities, then builds through speed, velocity and acceleration, distance-time and velocity-time graphs, Newton's three laws, weight and mass, circular motion, momentum and vehicle stopping distances. Examiners like multi-step calculations using a = (v - u) / t, F = m x a and v^2 - u^2 = 2 x a x x, graph interpretation, and the core practical on investigating acceleration. Higher tier students also meet inertial mass and force as rate of change of momentum.

What you need to know

• Scalars and vectors Scalars have magnitude only (speed, distance, mass, energy); vectors have magnitude and direction (velocity, displacement, force, acceleration, momentum).
• Motion graphs The gradient of a distance-time graph is speed. The gradient of a velocity-time graph is acceleration and the area under it is the distance travelled.
• Acceleration equations a = (v - u) / t, and v^2 - u^2 = 2 x a x x for uniform acceleration. Acceleration in free fall near the Earth's surface is about 10 m/s^2.
• Newton's laws First law: a resultant force is needed to change velocity. Second law: F = m x a. Third law: when two objects interact they exert equal and opposite forces on each other, of the same type.
• Weight and circular motion Weight = mass x gravitational field strength (W = m x g). An object moving in a circle at constant speed is accelerating because its direction changes, so a resultant centripetal force acts towards the centre.
• Momentum Momentum p = m x v and is conserved in collisions where no external forces act. Higher tier: force = change in momentum / time, which explains crumple zones, airbags and seat belts.
• Stopping distance Stopping distance = thinking distance + braking distance. Reaction time is affected by tiredness, drugs, alcohol and distractions; braking distance by speed, road and tyre condition and mass.
• Core practical Investigate how mass and force affect acceleration using a trolley, ramp and light gates, keeping the total mass constant when changing the force.

Common mistakes in Topic 2: Motion and Forces

• Saying an object moving in a circle at constant speed has no acceleration. Its velocity changes because its direction changes, so it is accelerating towards the centre.
• Describing Newton's third law pairs as acting on the same object, such as weight and the normal contact force on a book. Third law pairs act on different objects and are the same type of force.
• Reading the gradient of a velocity-time graph as distance. The gradient gives acceleration and the area gives distance.
• Using the word speed when a direction matters. Use velocity, and include a sign or direction, in momentum questions.
• Saying braking distance depends on reaction time. Reaction time affects thinking distance only.

Try three Topic 2: Motion and Forces exam-style questions