JEE MAIN - Physics (2023 - 11th April Morning Shift - No. 19)
The equation of wave is given by
$$\mathrm{Y}=10^{-2} \sin 2 \pi(160 t-0.5 x+\pi / 4)$$
where $$x$$ and $$Y$$ are in $$\mathrm{m}$$ and $$\mathrm{t}$$ in $$s$$. The speed of the wave is ________ $$\mathrm{km} ~\mathrm{h}^{-1}$$.
Explanation
Given the wave equation:
$$Y = 10^{-2} \sin 2 \pi(160t - 0.5x + \pi/4)$$
Comparing this equation with the general form:
$$Y = A \sin(2\pi(ft - kx + \phi))$$
We can identify the wave number $$k = 0.5\,\mathrm{m}^{-1}$$ and the frequency $$f = 160\,\mathrm{Hz}$$. The wave speed $$v$$ can be found using the relationship between wave number, wave speed, and frequency:
$$v = \frac{\omega}{k} = \frac{2\pi f}{2\pi k}$$
Now, we can calculate the wave speed:
$$v = \frac{2\pi \times 160}{2\pi \times 0.5} = \frac{160}{0.5}\,\mathrm{m/s}$$
$$v = 320\,\mathrm{m/s}$$
Now, we need to convert the wave speed from meters per second to kilometers per hour:
$$v = 320 \frac{\mathrm{m}}{\mathrm{s}} \times \frac{1\,\mathrm{km}}{1000\,\mathrm{m}} \times \frac{3600\,\mathrm{s}}{1\,\mathrm{h}}$$
$$v = 320 \times \frac{1}{1000} \times 3600\,\mathrm{km/h}$$
$$v = 1152\,\mathrm{km/h}$$
So, the speed of the wave is $$1152\,\mathrm{km/h}$$.
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