Question 2 - Comparing Two Runners - Questions at the end of the chapter - Chapter 8 Class 7 - Measurement of Time and Motion (Curiosity)

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?

Answer.

Use the formula: Speed = Distance ÷ Time

Speed of first runner:

$$\begin{aligned} \text{Speed}_1 &= \frac{\text{Distance}}{\text{Time}} \\[8pt] &= \frac{400 \text{ m}}{50 \text{ s}} \\[8pt] &= 8 \text{ m/s} \end{aligned}$$

Speed of second runner:

$$\begin{aligned} \text{Speed}_2 &= \frac{\text{Distance}}{\text{Time}} \\[8pt] &= \frac{400 \text{ m}}{45 \text{ s}} \\[8pt] &\approx 8.89 \text{ m/s} \end{aligned}$$

The second runner has the greater speed.

Difference = 8.89 − 8 = 0.89 m/s (approximately).