Physics tension question - help?

Question

A phone cord is 4.85 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?

Answer 1

The relationship between the tension in a cord, the linear density of the cord, and the velocity of a wave on the cord is given by

v = sqrt ( T / u )

where v is the velocity, T the tension, and u the linear density (that is, the mass of the cord divided by the length, with units of kg / m). Since the pulse makes four round trips ( 4 * length) in .780 seconds, you can compute the velocity. Now solve the above equation for the tension T.