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Unit 1 · Velocity and acceleration
Motion and forces · Year 10 Science · Science understanding
Topic hub: Overview · Next unit: Inertia and first law
This unit builds language for motion so Newton’s laws feel less abstract. It matches the idea that forces change how motion unfolds (see curriculum checklist).
Try it first
Play with starting velocity and constant acceleration, then Play. When does the block speed up, slow down, or change direction? The sections below give you the words and rules behind what you notice.
Interactive: velocity and constant acceleration
Use a preset for a clear pattern (loads values and runs Play), or set starting velocity and constant acceleration yourself. Positive is to the right.
Loading interactive…
1. What you should be able to do
- Distinguish distance and displacement, and speed and velocity, at a Year 10 level.
- Say what acceleration means (including slowing down as acceleration opposite to velocity).
- Connect non-zero acceleration to non-zero net external force (you will use this fully in Unit 3).
2. Distance, displacement and speed
- Distance is how far a path covers (scalar — a number with a unit, no direction needed for the size).
- Displacement is the straight-line change of position from start to finish, with direction in 1D problems (often shown as + or − along a line).
Speed is distance over time (average speed = total distance / total time). Velocity adds direction (in 1D, the sign tells you which way along the axis).
Same number, different story
If you run a lap and return to the start, average velocity for the lap can be zero (displacement = 0) even though average speed is not zero.
3. Acceleration
Acceleration is the rate of change of velocity. In one dimension:
- If velocity increases in the positive direction, acceleration is positive.
- If something slows down while moving in the positive direction, velocity is still positive for a while, but acceleration is negative (it points opposite to the motion).
So “acceleration” does not mean “speeding up” only — it means changing velocity.
Look back at Try it first: the arrow shows velocity direction; the caption relates v and a to what you saw on the track.
4. Bridge to forces (preview)
- If an object speeds up, slows down, or turns, its velocity is changing → acceleration is happening.
- In Newton’s second law (Unit 3), net external force on one object is tied to mass × acceleration. For now, remember: no net force along a line → no acceleration along that line (constant velocity, including rest — that is the first law, next unit).
5. Your turn
Q1. A skateboarder moves east at steady speed. Is acceleration zero or non-zero? In one sentence, why?
Sample answer
Zero — velocity is not changing (constant speed and direction), so acceleration is zero.
Q2. A car moves north and brakes. While it is still moving north but slowing, is the northward component of acceleration positive or negative?
Sample answer
Negative (if north is the positive direction) — acceleration opposes the forward motion while the car slows.
Q3. Give one difference between speed and velocity in your own words.
Sample answer
Speed is how fast you move along a path; velocity includes direction (e.g. “3 m/s north” is velocity; “3 m/s” alone is speed).