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Kinematics and Motion: SPI Physics

Kinematics and Motion has 7 questions in the SPI bank, and two of them are from the 2022 paper. Four are EASY, two MODERATE and one HARD. Most of them test whether you read a word or a graph exactly: distance against displacement, an average against a mean of two speeds, a flat line on one graph against a flat line on another. These pages build those distinctions first and then add the three equations of motion.

The handout has every subtopic, worked example, formula and trap with answers shown. The formula sheet is the chapter’s formulas and traps alone, on one page.

SPI home All formulas on one page

Subtopic notes

Formula & revision sheet

4 formulas · 2 reference tables · 11 gotchas across all subtopics — the exam-eve cheat-sheet

Distance, Displacement and Speed

Formulas (2)

Distance and displacement · Distance and displacement $\text{displacement} \le \text{distance} \qquad \text{circumference of a circle} = 2\pi r$
Average speed over two or more parts of a journey · Average speed $\text{average speed} = \frac{\text{total distance}}{\text{total time}} \qquad 1\ \text{km/h} = \frac{5}{18}\ \text{m/s}$

Reference tables (1)

Rest and motion depend on what you compare with3 rows

Body	At rest compared with	In motion compared with
A passenger sitting in a moving bus	The bus and the other passengers	The road and the trees outside
A tree by the road	The ground	A passenger in a passing bus
A pilot flying a plane	The plane	The ground

Answer 'rest or motion?' with both, once you name the two reference points.

Watch out for (5)

Picking only one of rest and motion
→ Rest and motion depend on what you compare with
Giving the arc length as the displacement
→ Distance and displacement
Thinking a full round is far away
→ Distance and displacement
Averaging the two speeds
→ Average speed over two or more parts of a journey
Using minutes with km/h
→ Average speed over two or more parts of a journey

Motion Graphs and Equations of Motion

Formulas (2)

Slope and area of a velocity-time graph · Velocity-time graph $a = \text{slope} = \frac{v - u}{t} \qquad \text{distance} = \text{area under the graph}$
The three equations of motion and a body thrown upwards · Equations of motion $v = u + at \qquad s = ut + \tfrac{1}{2}at^2 \qquad v^2 = u^2 + 2as \qquad u = \sqrt{2gh} \text{ to reach height } h$

Reference tables (1)

What the shape of each motion graph means7 rows

Graph	Line shape	What the motion is
Distance against time	Flat	At rest
Distance against time	Straight, sloping up	Constant speed
Distance against time	Curving upwards	Speeding up
Velocity against time	Flat (above zero)	Constant velocity, so constant speed
Velocity against time	Straight, sloping up	Constant acceleration, speed changing
Speed against time	Straight, sloping up	Speed rising steadily
Acceleration against time	Flat (above zero)	Constant acceleration, speed changing

Constant speed shows up as a sloping distance-time line or a flat speed or velocity-time line.

Watch out for (6)

Reading a flat acceleration line as constant speed
→ What the shape of each motion graph means
Reading a flat distance-time line as constant speed
→ What the shape of each motion graph means
Mixing up slope and area
→ Slope and area of a velocity-time graph
Comparing two bodies by their speed at one moment
→ Slope and area of a velocity-time graph
Forgetting the speed at the top is zero
→ The three equations of motion and a body thrown upwards
Using the equations when acceleration changes
→ The three equations of motion and a body thrown upwards

Question weightage by concept

6 concepts · 7 questions — where the marks actually sit, so you know what to drill first

Distance, Displacement and Speed3 questions · 43%

Concept	Qs	Share
Rest and motion depend on what you compare with	1	14%
Distance and displacement	1	14%
Average speed over two or more parts of a journey	1	14%

Motion Graphs and Equations of Motion4 questions · 57%

Concept	Qs	Share
Slope and area of a velocity-time graph	2	29%
What the shape of each motion graph means	1	14%
The three equations of motion and a body thrown upwards	1	14%

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