Practice questions · Speed and velocity

One equation, used carefully.

Six original Cambridge-style questions on the speed-versus-velocity distinction, average speed, and v = s / t, with the unit conversions that protect your marks.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Before you substitute

Metres, seconds, then divide.

Convert km to m and minutes to s before using v = s ÷ t.
Average speed = total distance ÷ total time, not the average of the speeds.
Velocity needs a direction; speed does not.

[2 marks]

Define speed, and state its SI unit.

Speed is the distance travelled per unit time. ✓
SI unit: metre per second (m/s). ✓

Analysis

[2 marks]

Explain the difference between speed and velocity, using an example.

Speed is a scalar (magnitude only); velocity is a vector (speed in a stated direction). ✓
Example: 20 m/s is a speed; 20 m/s due north is a velocity. ✓

Calculation

[2 marks]

A runner covers 240 m in 30 s at a steady rate. Calculate the speed.

v = s ÷ t = 240 m ÷ 30 s

v = 8.0 m/s

Calculation

[3 marks]

A train travels 3.0 km in 10 minutes. Calculate its average speed in m/s.

Convert first. 3.0 km = 3000 m; 10 min = 600 s.

v = 3000 m ÷ 600 s

v = 5.0 m/s

Calculation

[4 marks]

A walker covers the first 60 m of a path at 3.0 m/s, then the next 60 m at 6.0 m/s. Calculate the average speed for the whole 120 m.

Time for each part.

t₁ = 60 ÷ 3.0 = 20 s ; t₂ = 60 ÷ 6.0 = 10 s

Average. total distance ÷ total time = 120 m ÷ 30 s

average speed = 4.0 m/s

not 4.5 m/s; you cannot just average 3 and 6

Analysis

[2 marks]

Two cars drive along the same straight road at 25 m/s, but in opposite directions. State whether their speeds are the same and whether their velocities are the same, explaining your answer.

Their speeds are the same (both 25 m/s), because speed has magnitude only. ✓
Their velocities are different, because velocity includes direction and they travel in opposite directions. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.