Speed

• Speed as distance travelled per unit time — the basic formula v = distance ÷ time.
• To calculate speed when distance and time are given in consistent units.
• The difference between uniform speed and changing speed in daily motion.
• To compare speeds of athletes, vehicles, and animals using the same unit (m/s or km/h at intro level).

Level 1 — What speed means

Verbal: Speed tells how fast something moves — more distance in the same time means higher speed.

Symbolic: speed = distance / time, or v = s/t.

Visual:

Runner A is faster (5 > 4 m/s).

Units: m/s (metre per second) in SI; km/h common for cars. Always state the unit.

Level 2 — Calculations and comparisons

Uniform speed: Speed stays constant — rare in real traffic but useful in textbook problems.

Average speed (intro): total distance ÷ total time for whole journey.

Example: 120 km in 2 h → average speed = 120/2 = 60 km/h.

Unit consistency: Convert before dividing — 1 km = 1000 m; 1 h = 3600 s (Class 6 may use km/h and m/s separately).

Faster/slower: Compare only when units match — 72 km/h vs 20 m/s needs conversion.

A cyclist covers 3 km in 15 minutes. Find speed in km/h and m/s.

Step 1 — Time: 15 min = 15/60 h = 0.25 h
Step 2 — Speed (km/h): 3 ÷ 0.25 = 12 km/h
Step 3 — Speed (m/s): 12 km/h = 12000 m / 3600 s ≈ 3.33 m/s

• Write the formula for speed and define each symbol.
• A train travels 180 km in 3 hours. Find its average speed.
• Who is faster: 10 m in 2 s or 15 m in 4 s? Show calculation.
• Why is average speed useful for a bus that stops at stations?

Open the Practice tab for graded questions on Speed.