posted by diamond .
A phone cord is 4.25 m long. The cord has a mass of 0.200 kg. A transverse wave pulse is produced by plucking one end of the taut cord. The pulse makes four trips down and back along the cord in 0.780 s. What is the tension in the cord?
The wave speed is
v = 2*4*4.25/0.78 = 43.5 m/s
The mass per unit length of the cord is a = 0.04706 kg/m
The wave speed is related to tension force T by the equation
v = sqrt(T/a)
Solve for T
T = a v^2 = 89 Newtons