In: Physics
A 2.40-m-long pulse is travelling at a speed of 5.75 m/s in a spring. How long does it take the pulse to pass any point on the spring?
The length of the pulse is L=2.40m
Speed of pulse is v=5.75m/s
We want to find the time in which the pulse passes through a point on the spring. Since the length of the pulse in constant and the speed with which it is moving is also constant, the time taken is given by
You can think of the pulse as a stick of constant length L=2.40m moving at constant speed v=5.75m/s. And we want to determine the time in which it passes through a stationary point P(as shown in the figure below).
Stick moving
In reference frame of the stick, the stick is at rest and point P is moving towards the stick (shown in the figure below). The point appear to move at speed v=5.75m/s. The time taken by the stationary point in passing through the length of the stick is T=L/v=2.40m/5.74m/s=0.414s.