Question

A telephone cord is 6.20 m long and has a mass of 0.220 kg. A transverse pulse is produced by plucking one end of the taut cord. The pulse makes four trips down and back along the cord in 0.830 s. What is the tension in the cord?

Answer 1

The wave makes 4 round trips in 0.83 s, so the wave speed is:
V = 8*6.2 m/0.83 s = 59.8 m/s

The mass per unit length is
s = 0.0355 kg/m

sqrt(T/s)= V

Then solve for T.
T = s * V^2 = 127 Newtons