A 4.0 kg block is suspended from the ceiling of an elevator through a string having a linear mass density of 19.2×10 kg m−1. Find the speed (with respect to the string) with which a wave pulse can proceed on the string if the elevator accelerates up at the rate of 2.0 ms−2. Take g=10 ms−2.
m=19.2×10−3kg/m
From the freebody diagram,
T - 4g - 4a = 0
⇒T=4(a+g)
=4(2+10)=48 N
Wave speed, v=√(Tm)
=(4819.2×103)
=√(2.5×10−3)=50 m/s