a student fixes two end of a rope to two rigid supports A and B placed at a distance of 7.5 m . He gives a transversal horizontal jerk to create a pulse in the rope which moves from A to B , B to A , again from A to B and B to A and so on . the movement he gives jerk to the rope his friend immediately starts the stopwatch . The pulse dies after completing three to and fro journeys from A to B and back . The pulse takes 1 min and 15 sec to complete its entire journey . What is the speed of the pulse moving on the rope ?
Length of the rope, AB = 7.5 m
In 1min and 1.5 s the pulse moves from A to B then B to A three times.
So, distance travelled is, d = 3 X 7.5 = 22.5 m
Time taken, t = 75 s
Speed of the wave, v = d/t = 0.3 m/s