CIE A Level Physics
CIE A Level Physics Dynamics Exam Questions
Free CIE A Level Physics exam questions for Dynamics, with a mark scheme for every pack. Covers momentum, Newton's laws of motion, weight and mass, drag and terminal velocity, and conservation of momentum in collisions.
Dynamics exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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A-Level Physics Flashcards for 2027 Onwards
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Then test yourself with the questions on this page.
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About CIE A Level Physics Dynamics
Dynamics is Topic 3 of the Cambridge International AS & A Level Physics (9702) syllabus. It explains motion using forces and momentum. Newton's second law is defined in terms of rate of change of momentum, and you apply conservation of momentum to collisions and explosions in one and two dimensions. The topic also covers drag forces and terminal velocity. It builds on Kinematics and links to Work, energy and power and to Motion in a circle. Examiners like to test Newton's third law pairs, elastic and inelastic collisions, and explanations of terminal velocity.
What you need to know
- Momentum Linear momentum p = mv, a vector measured in kg m s^-1 (or N s). Resultant force equals rate of change of momentum, F = Δp/Δt, which reduces to F = ma for constant mass.
- Newton's laws First law: an object stays at rest or at constant velocity unless a resultant force acts. Third law: if body A exerts a force on B, B exerts an equal and opposite force of the same type on A.
- Mass and weight Mass is the property of a body that resists change in motion. Weight is the gravitational force on it, W = mg.
- Drag and terminal velocity Drag increases with speed. A falling object reaches terminal velocity when drag plus upthrust equals weight, so the resultant force and acceleration are zero.
- Conservation of momentum Total momentum of a system is constant if no resultant external force acts. In a perfectly elastic collision, kinetic energy is also conserved and the relative speed of approach equals the relative speed of separation.
- Two dimensions In 2D problems, apply conservation of momentum separately to perpendicular components.
Common mistakes in Dynamics
- Naming weight and the normal contact force as a Newton's third law pair. Third law pairs act on different bodies and are the same type of force.
- Saying kinetic energy is conserved in all collisions. Momentum is always conserved in a closed system, but kinetic energy is conserved only in perfectly elastic collisions.
- Ignoring direction when using conservation of momentum. Velocities in opposite directions must have opposite signs.
- Saying an object at terminal velocity has no forces acting on it. The forces are balanced, so the resultant force is zero.
- Writing F = ma as the definition of force. Cambridge defines force as rate of change of momentum.
Try three Dynamics exam-style questions
1. A trolley of mass 2.0 kg moving at 3.0 m s^-1 collides with a stationary trolley of mass 1.0 kg and they stick together. Calculate the common velocity and the loss of kinetic energy. (4 marks)
Show the mark scheme answer
Momentum before = 2.0 × 3.0 = 6.0 kg m s^-1; v = 6.0/3.0 = 2.0 m s^-1; KE before = ½ × 2.0 × 3.0^2 = 9.0 J; KE after = ½ × 3.0 × 2.0^2 = 6.0 J; loss = 3.0 J.
2. Explain why a skydiver falling from rest reaches a terminal velocity. (3 marks)
Show the mark scheme answer
Initially only weight acts so acceleration is g; as speed increases air resistance increases so resultant force and acceleration decrease; when air resistance equals weight the resultant force is zero and velocity is constant.
3. State two properties of a pair of forces described by Newton's third law. (2 marks)
Show the mark scheme answer
Equal in magnitude and opposite in direction; act on different bodies; same type of force (any two).
Dynamics FAQs
What does Cambridge AS & A Level Physics Dynamics cover?
It covers momentum, Newton's three laws, mass and weight, drag and terminal velocity, and conservation of momentum including elastic and inelastic collisions.
Which papers is Dynamics examined in?
It is an AS Level topic assessed in Paper 1 and Paper 2, and the ideas are needed again in A Level topics such as Motion in a circle.
How do I check whether a collision is elastic?
Calculate the total kinetic energy before and after; if it is unchanged the collision is perfectly elastic, and the relative speed of approach will equal the relative speed of separation.
