Question

Figure 21.4a is a snapshot of graph at t=0s of two waves approaching each other at 1.0m/s.

a. At what time was the snapshot graph in 21.4b taken?

b. Draw a history graph of the string at x=5.0m from t=0s to t=6s.

Answer 1

Use the principle of superposition to find the snapshot graph of two waves at given instant of time.

(a)

The following graph shows snapshot after 4.0 s. The dotted lines on the graph show the positions of each individual wave. Due to there being some overlap at this point in time there is a net displacement due to superposition.

$C:\Users\mangadevi\Desktop\snap1.jpg$

The best way to find this position is to notice that the right side has the shape of the right side of the object that was intially on the left. This shows that the waves have be already bugun to move past eachother. Since the wave is moving at 1.0 m/s and the right hand side has move from x = 3 m to x = 7 m, 4 seconds must have passed.

Therefore, the figure Ex21.4b is the snapshot of figure Ex21.4a at.

(b)

The history graph of snapshot graph at 5 m is shown below.

$C:\Users\mangadevi\Desktop\sige.jpg$