Equations of motion
Cambridge A-Level Physics (9702) · Unit 2: Kinematics · 10 flashcards
Equations of motion is topic 2.1 in the Cambridge A-Level Physics (9702) syllabus , positioned in Unit 2 — Kinematics . In one line: Displacement is the shortest distance from the initial to the final position, along with the direction. Distance is the total length of the path traveled. Displacement is a vector, while distance is a scalar.
Marked as AS Level: examined at AS Level in Paper 1 (Multiple Choice), Paper 2 (AS Structured Questions) and Paper 3 (Advanced Practical Skills). The same content may also be assumed in Paper 4 (A Level Structured Questions).
The deck below contains 10 flashcards — 5 definitions, 4 key concepts and 1 calculation — covering the precise wording mark schemes reward. Use the 5 definition cards to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
Some cards in this deck are on other syllabus topics: 3.1 Momentum and Newton’s laws of motion. Each card is labelled with its topic.
Displacement and how it differs from distance
Displacement is the shortest distance from the initial to the final position, along with the direction. Distance is the total length of the path traveled. Displacement is a vector, while distance is a scalar.
What the Cambridge 9702 syllabus says
2025-2027 syllabus, in our words · AS LevelWhat the syllabus expects you to be able to do in this topic, in plain English. For the exact wording, see the official syllabus (PDF).
- Define the quantities acceleration, velocity, speed, displacement and distance, and use them in calculations.
- Plot or sketch graphs to represent distance and displacement, speed and velocity, and acceleration.
- Work out displacement as the area beneath a velocity-time graph.
- Work out velocity as the gradient of the graph of displacement against time.
- Work out acceleration as the gradient of the graph of velocity against time.
- Starting with how velocity and acceleration are defined, derive the equations for uniformly accelerated motion along a straight line.
- Solve problems with the equations for uniformly accelerated straight-line motion, including objects falling freely in a uniform gravitational field when air resistance is ignored.
- Describe an experiment that uses a falling object to measure the free-fall acceleration g.
- Describe and explain the motion of an object that has a constant velocity in one direction combined with a constant acceleration at right angles to it.
Also in this deck: 3.1 Momentum and Newton’s laws of motion
- Understand mass as the property that makes an object resist any change in its motion.
- Recall F = ma and use it to solve problems, understanding that the acceleration always points the same way as the resultant force.
- Define linear momentum as mass multiplied by velocity, and use this definition.
- Define force as how fast momentum changes (F = Δp / Δt), and use this definition.
- State each of Newton's three laws of motion and apply them.
- Describe and use the idea that weight is the effect a gravitational field has on a mass; also recall that weight is mass multiplied by g, the free-fall acceleration (W = mg).
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9702 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Tips to avoid common mistakes in these topics
- › Check the plane of motion; only use 'g' for vertical motion or components of motion on a slope, never for horizontal travel.
- › Always treat horizontal and vertical components independently; for a horizontally projected object, the initial vertical velocity (uy) is 0.
- › Recall that average velocity is displacement divided by time; if an object returns to its starting position, its displacement and average velocity are zero.
- › Distinguish between distance (scalar) and displacement (vector); displacement must account for the change in direction and return to the starting point.
- › Use the precise syllabus definition: acceleration is 'change in velocity per unit time' or 'rate of change of velocity'.
Topic 2.1 · Equations of motion
Define displacement and how it differs from distance.
Displacement is the shortest distance from the initial to the final position, along with the direction. Distance is the total length of the path traveled. Displacement is a vector, while distance is a scalar.
Topic 2.1 · Equations of motion
What is the definition of acceleration?
Acceleration is the rate of change of velocity with respect to time. It is a vector quantity, meaning it has both magnitude and direction. Mathematically, it's defined as a = Δv/Δt.
Topic 2.1 · Equations of motion
Describe how to determine displacement from a velocity-time graph.
The displacement is equal to the area under the velocity-time graph. If the velocity is negative at any point, that area below the x-axis is negative displacement.
Topic 2.1 · Equations of motion
How is velocity determined from a displacement-time graph?
The velocity at any point on a displacement-time graph is equal to the gradient (slope) of the graph at that point. The gradient indicates the rate of change of displacement with respect to time.
Topic 2.1 · Equations of motion
State the equations of uniformly accelerated motion in a straight line (SUVAT equations).
The SUVAT equations are: v = u + at, s = ut + (1/2)at², v² = u² + 2as, and s = (u+v)t/2, where s=displacement, u=initial velocity, v=final velocity, a=acceleration, and t=time.
Topic 2.1 · Equations of motion
Describe an experiment to determine the acceleration of free fall using a falling object and a trapdoor.
An electromagnet holds a steel ball. When the current is cut, the ball is released and a timer starts. The ball falls a measured distance (s) and hits a trapdoor, stopping the timer. Using s = ut + (1/2)gt² (u=0), g ≈ 2s/t² is calculated.
Topic 2.1 · Equations of motion
Explain how the horizontal and vertical components of projectile motion are treated separately.
In projectile motion, the horizontal component of velocity is constant (assuming no air resistance) as there's no horizontal acceleration. The vertical component is affected by gravity (constant downward acceleration 'g'). These are analyzed independently and then combined to describe the overall motion.
Topic 3.1 · Momentum and Newton’s laws of motion
State Newton's First Law of Motion.
An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by a net force.
Topic 3.1 · Momentum and Newton’s laws of motion
Define linear momentum and its SI unit.
Linear momentum (p) is the product of an object's mass (m) and its velocity (v): p = mv. Its SI unit is kg m/s.
Topic 3.1 · Momentum and Newton’s laws of motion
State Newton's Second Law of Motion in terms of momentum.
Newton's Second Law states that the resultant force acting on an object is equal to the rate of change of its momentum: F = Δp/Δt.
Review the material
Read full revision notes on Equations of motion — definitions, equations, common mistakes, and exam tips.
Read NotesKey terms covered in this Equations of motion deck
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