A phone cord is 6.16 m long. The cord has
a mass of 0.261 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 0.921 s.
What is the tension in the cord?
Answer in units of N.

121.10N

Explanation:

Velocity= square root of (tension/mass per length)

The velocity can be found by the total length over the total time (v=x/t). There were 4 trips there and back. That is, 8 total lengths (4 one way 4 the other) of the rope.

8 trips × 6.16m= 49.28m in total.

The total time is given as 0.921secs

So, 49.28/0.921= 53.507m/s.

Mass per length is given as:

0.261/6.16= 0.0423kg/m

Make tension the subject of the formula.

Tension= (mass per length) × (velocity^2)

Tension= (0.0423kg/m) × (53.507m/s)^2

Tension= 121.10N

Therefore, the tension of the cord is 121.10N