Uniform

Uniform Motion & Speed

What you'll learn

Uniform motion — object covers equal distances in equal intervals of time.
Speed = distance ÷ time; units m/s or km/h.
Distinguishing uniform from non-uniform motion (changing speed).
Using stopwatch and metre scale for school track measurements.
Real examples: clock hand tip (approximate), train at steady speed on straight track.
Formula practice with Indian units: km/h for vehicles, m/s for lab experiments.

Key concepts

Level 1 — Core idea

Speed (v) — distance travelled per unit time: v = d / t.
Uniform motion — speed constant; equal steps on track each second.
Non-uniform — car in city traffic; athlete after sprint start.

Level 2 — Process and representation

Unit conversion — km/h to m/s: multiply by 5/18 (e.g. 36 km/h = 10 m/s).
Diagram (text) — toy car at 0 m, 2 m, 4 m, 6 m at t = 0, 1, 2, 3 s → uniform.
Average speed — total distance / total time (for non-uniform overall trip).

Level 3 — Applications and NCERT links

NCERT Activity 13.2 — measure distance of school bus or walk a fixed path with stopwatch.
Real world — Odometer shows distance; speedometer shows instantaneous speed in car.
SI unit of speed — metre per second (m/s).

Worked example

Calculating speed of a cyclist on a 2 km school route

Given: total distance = 2 km = 2000 m; time taken = 8 minutes = 8 × 60 = 480 s.
Step 1 — Write formula: speed = distance / time.
Step 2 — Substitute: v = 2000 m / 480 s = 4.17 m/s (approx).
Step 3 — Convert to km/h: 4.17 × (18/5) ≈ 15 km/h.
Step 4 — Check reasonableness: cycling pace ~12–18 km/h ✓
Step 5 — If return trip also 2 km in 10 min, average speed for full 4 km:
         total d = 4 km, total t = 18 min → avg speed = 4/0.3 ≈ 13.3 km/h.
Step 6 — Uniform motion means each minute covers same distance (ideal case).
Step 7 — Record units at every step to avoid km/s confusion.
Conclusion: speed compares how fast different journeys are completed.

Common mistakes

Misconception	What students think	Scientific correction
Formula reversed as time / distance.	Formula reversed as time / distance.	Check the Key concepts and worked example for the NCERT-accurate version.
Mixing km with seconds without converting.	Mixing km with seconds without converting.	Check the Key concepts and worked example for the NCERT-accurate version.
Assuming motion is uniform without checking equal dista	Assuming motion is uniform without checking equal distances per equal time.	Check the Key concepts and worked example for the NCERT-accurate version.
Forgetting average speed uses total distance and to	Forgetting average speed uses total distance and total time, not average of two speeds.	Check the Key concepts and worked example for the NCERT-accurate version.
Instantaneous speed** equals average always (only same	Instantaneous speed** equals average always (only same for uniform).	Check the Key concepts and worked example for the NCERT-accurate version.
Adding speeds directly for to-and-fro trip.	Adding speeds directly for to-and-fro trip.	Check the Key concepts and worked example for the NCERT-accurate version.

Quick check

Define uniform motion.
A car travels 150 km in 3 h. Find speed in km/h.
Convert 72 km/h to m/s.
Is a bouncing ball in uniform motion? Why?
Write the formula for speed with units.
A train covers 120 km in 2 h uniformly. Find speed.

Open the Practice tab for graded questions on Uniform Motion & Speed.

Uniform

Uniform

Uniform Motion & Speed

What you'll learn

Key concepts

Level 1 — Core idea

Level 2 — Process and representation

Level 3 — Applications and NCERT links

Worked example

Common mistakes

Quick check

Key Takeaways (TL;DR)

Master this topic with Drishti OS