Question

A person moved from A to B on a circular path as shown in figure. If the distance travelled by him is 60 m, then the magnitude of displacement would be
(Given cos135°= –0.7)

• A. 42 m
• B. 47 m
• C. 19 m
• D. 40 m

Answer 1

Answer: (B)

47 m

Answer 2

Distance travelled = 60 m
⇒ Angle covered = 135° d=Rθ
60=$\frac{R^3\pi}{4}$
R=$\frac{60\times4}{3\pi}$=$\frac{80}{\pi}$m
Displacement =$\sqrt{R^2+R^2-2R^2cos135}$
⇒$\sqrt{3.4R^2}$=$\frac{3.4\times 80^2}{\pi}$≈47 m