A person moved from \(A\) to \(B\) on a circular path as shown in figure. If the distance travelled by him is \(60 ~\text{m}\), then the magnitude of displacement would be (Given \(\cos 135^{\circ}= –0.7\))

Distance travelled \(= 60 ~\text{m}\)

\(\Rightarrow\) Angle covered \(= 135^{\circ}\)

Displacement \(AB~=\sqrt{R^2+R^2-2R^2\cos 135^\circ}\)

\(=2 \left(\dfrac{60}{135} \times \dfrac{180}{\pi}\right)
\left[\dfrac{1-\cos (135^{\circ})}{2}\right]^{1/2}\)

\(=2 \left(\dfrac{80}{\pi}\right) (0.85)^{1/2}\approx 47~\text{m}\)

Hence, \((B)\) is the correct answer.