Question 2 - A runner completes 400 metres in 50 seconds - Questions at the end of the chapter - Chapter 8 Class 7 - Measurement of Time and Motion (Curiosity)

Last updated at August 14, 2026 by

Q 2
Question
A runner completes 400 metres in 50 seconds. Another runner completes the same distance in 45 seconds. Who has a greater speed and by how much?

🔗 Concept: 8.3 Speed

Two runners, 400 m — who is faster and by how much? Question 2 - A runner completes - Measurement of Time an - Class 7 (Cu - Questions at the end of the chapter
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Runner B (45 s) is faster by ≈ 0.89 m/s

Explanation

📋 Given
  • Runner A: distance = 400 m, time = 50 s
  • Runner B: distance = 400 m, time = 45 s
🔄 Unit Conversion
  • No conversion needed — distance in m, time in s → speed in m/s.
📐 Formula

Speed = Distance ÷ Time

Step 1 — Speed of Runner A
$$\text{Speed}_A = \frac{400 \text{ m}}{50 \text{ s}} = 8 \text{ m/s}$$
Step 2 — Speed of Runner B
$$\text{Speed}_B = \frac{400 \text{ m}}{45 \text{ s}} \approx 8.89 \text{ m/s}$$
Step 3 — Compare

Runner B has a higher speed (less time for same distance).

$$\text{Difference} = 8.89 - 8 = \boxed{0.89 \text{ m/s}}$$
Runner B is faster — 8.89 m/s vs 8 m/s, difference ≈ 0.89 m/s.
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