Q: A 4 kg block is suspended from the ceiling of an elevator through a string having a linear mass density of 19.2 × 10^{-3} kg m^{-1}. Find the speed with which a wave pulse can travel on the string if the elevator accelerates up at 3 ms^{-2}? (g = 10 ms^{-2})

Sol: $\large v = \sqrt{\frac{T}{\mu}}$

$\large v = \sqrt{\frac{M(g+a)}{\mu}}$

$\large v = \sqrt{\frac{4(10 + 2)}{19.2 \times 10^{-3}}}$

v = 50 m/s