A phone cord is 6.48 m long. The cord has a mass of 0.253 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 0.877 s. What is the tension in the cord

136.27 N

Explanation:

From the question,

The velocity of the pulse is given as

v = L/t ... Equation 1

Where v = velocity of the pulse, L = total length of the pulse, t = time.

Given: L = 4*2*6.48 (as the pulse makes four tips down and back) = 51.84 m, t = 0.877 s.

substitute into equation 1

v = 51.84/0.877

v = 59.11 m/s.

Using,

But,

v = √ (T/m') ... Equation 2

Where T tension in the cord, m' = mass per unit length of the cord.

make T the subject of the equation

T = v²m' ... Equation 3

Given: v = 59.11 m/s, m' = 0.253/6.48 = 0.039 kg/m

Substitute into equation 3

T = 59.11² (0.039)

T = 136.27 N

Hence the tension in the cord = 136.27 N