Question

Following figure 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.

Answer 1

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:

\[In  t = 4  ms = 4 \times  {10}^{- 3}   s, \] 

\[s = \nu t = 500 \times 4 \times  {10}^{- 3}  = 2  mm . \] 

\[In  t = 6  ms = 6 \times  {10}^{- 3}   s, \] 

\[s = 500 \times 6 \times  {10}^{- 3}  = 3  mm . \] 

\[In  t = 8  ms = 8 \times  {10}^{- 3}   s, \] 

\[s = \nu t = 500 \times 8 \times  {10}^{- 3}  =   4  mm . \] 

\[In  t = 12  ms = 12 \times  {10}^{- 3}   s, \] 

\[s = 500 \times 12 \times  {10}^{- 3}  = 6  mm .\]
The shapes of the string at different times are shown in the above.