Q 11-14-136JEE MainJEE Main 2017 (9 Apr)Easy
A standing wave is formed by the superposition of two waves travelling in opposite directions. The transverse displacement is given by $y(x, t) = 0.5\sin\left(\dfrac{5\pi}{4}x\right)\cos(200\pi t)$. What is the speed of the travelling wave moving in the positive $x$ direction? ($x$ and $t$ are in meter and second, respectively)
Answer: (C) $160\ \text{m s}^{-1}$
Each component wave has the same $k$ and $\omega$ as the standing wave:
$$v = \frac{\omega}{k} = \frac{200\pi}{5\pi/4} = 160\ \text{m s}^{-1}$$
Solution by Sreeraj P, M.Sc Physics