Question

Figure (15-E7) shows two wave pulses at t = 0 travelling on a string in opposite directions with the same wave speed 50 cm s−1. Sketch the shape of the string at t = 4 ms, 6 ms, 8 ms, and 12 ms.
Figure

Answer 1

Distances travelled by Pulse, S = VT

Explanation:

Given,

Speed of the wave pulse travelling in the opposite direction, v = 50 cm $s^-1$ = 500 mm $s^-^1$

Distances travelled by the pulses:

Using s = vt, we get:

In t = 4 ms = $4 \times 10^-^3$ s,  

s = $\nu t$ = 500  $4\times 10^-^3$ =2 mm.

In t = 6 ms = 6 $\times10^-^3$ s,

s = $500\times6 \times10^-^3$ = 3 mm.

In t = 8 ms = 8 $\times10^-^3$s,

s = $\nu t$= 500 $\times8 \times10^-^3$ = 4 mm.

In t = 12 ms = $12 \times10^-^3$s,

s = $\nu t$ = $500 \times12 \times10^-^3$ = 6 mm.

The shapes of the string at different times are shown in the figure.