Answer:
1.81 s
Explanation:
From the given information:
The links between the cars are:
1-2, 2-3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10, 10-11, 11-12, 12-13, 13-14, 14-15, 15-16, 16-17, 17-18, 18-19, 19-20.
where;
1 denotes the first car that joins strongly attached to the engine.
There are 19 links from the above connections and each one of them has a 2 cm slack.
Thus; the total slack = 2 × 19 = 38 cm
However, the speed of the train = 21 cm/s
Then, the time taken by the pulse to travel the length of the train is expressed by using the formula:
= length / speed
= 38 / 21
= 1.81 seconds
Thus, the required time = 1.81 s
