Question

If a boy moves along the boundary of a square field of side 20 m in 40 s. What will be the magnitude of displacement of the boy at the end of 4 minutes 20 seconds?

• A. 24.12 m
• B. 28.28 m
• C. 26.12 m
• D. 25.48 m

Answer 1

The correct option is B

28.28 m

Perimeter of the field = 4 * side = 4 * 20 m = 80 m

Speed of the boy = $\frac{80}{40}$ = 2 m/s

In 4 min 20 s, distance moved = 2 * (4 * 60 + 20) = 2 * 260 = 520 m

No. of rounds completed = $\frac{520}{80}$ = 6.5 rounds

Hence displacement = AC = $\sqrt{({20}^2+{20}^2)}$ = 28.28 m