Motion: Uniform, Non-Uniform, Speed and Average Speed: quick revision, 17 bites

Uniform vs Non-Uniform: The Core Test

Equal distance in equal time? That's the test.

The entire topic rests on one question: **does the object cover equal distances in equal time intervals?**

Takeaway. If distances in equal time intervals differ, the motion is non-uniform — no exceptions.

Defining Uniform and Non-Uniform Motion

Two definitions that unlock every question.

Takeaway. Uniform = equal distances in equal time; Non-uniform = unequal distances in equal time.

The Three Core Formulas of Motion

Three formulas solve almost every problem.

Takeaway. Speed, distance and time form a triangle — know any two, find the third.

Average Speed: Total Over Total

Never average the speeds — average the totals.

Takeaway. Average speed uses total distance and total time — not the mean of individual speeds.

The Average Speed Trap

Don't just add and divide the speeds.

Takeaway. Average speed is total distance divided by total time — never the simple mean of speeds.

Multi-Segment Journey: Step-by-Step Method

Break the journey into segments.

When a vehicle moves at different speeds over different parts of a journey, solve it in **five clean steps**.

Takeaway. Segment the journey, find each time, then use the remaining distance and time to find the unknown speed.

Worked Example: 2 km in 200 s

500 m at 10 m/s, 500 m at 5 m/s — now what?

Required speed for the last 1000 m in 50 s = 1000 ÷ 50 = **20 m/s**. Average speed = 2000 ÷ 200 = **10 m/s**.

Takeaway. Remaining time = total time − time already used; then speed = remaining distance ÷ remaining time.

Reading Motion Data from a Table

The table tells you the motion type.

To classify motion from a time–distance table, check whether the **distance covered in each equal time interval is the same**.

Takeaway. Equal gaps in distance per equal time interval = uniform; unequal gaps = non-uniform.

Uniform vs Non-Uniform: Real-Life Examples

Highway vs city traffic — spot the difference.

Takeaway. Real life is mostly non-uniform — traffic, rough roads and crowds constantly change speed.

Non-Uniform Motion Dominates Daily Life

Real life rarely moves at constant speed.

**Non-uniform motion is more common** in daily life than uniform motion, because speed constantly changes due to traffic, rough roads, turns and stops.

Takeaway. Uniform motion is the exception; non-uniform motion is the everyday rule.

km/h ↔ m/s in One Step

Multiply by 5/18 — done.

Takeaway. 5/18 converts km/h → m/s; 18/5 converts m/s → km/h.

Worked Example: Train Speed Conversion

180 km in 3 h — speed in two units.

Takeaway. Once speed is found, distance for any time = speed × time.

Worked Example: Comparing Two Speeds

Horse vs train — who wins?

A galloping horse runs at **18 m/s**. A train moves at **72 km/h**. Convert the train's speed to compare.

Takeaway. Always convert to the same unit before comparing two speeds.

Unit Mismatch Disaster

Mixing km and m ruins the answer.

Takeaway. Match units before dividing — km with km/h, m with m/s.

Exam Strategy for Motion Problems

Write the formula before you calculate.

Takeaway. A clean table of segments and consistent units prevents most exam errors.

Remember the Speed Triangle

One triangle, three formulas.

Picture a triangle with **D on top** and **S and T at the bottom**. Cover the one you want — the arrangement of the other two gives the formula.

Takeaway. The D-S-T triangle instantly recalls all three motion formulas.

Why 'Average Speed' Isn't the Mean

Same distance, different speeds — not 7.5.

If a vehicle covers 500 m at 10 m/s and another 500 m at 5 m/s, the simple mean of 10 and 5 is 7.5 m/s — but the **true average speed is 6.67 m/s** (1000 m ÷ 150 s).

Takeaway. Time-weighting is why average speed ≠ simple mean of speeds.