Concepts Of Physics MCQ Edition [Volume 1]PhysicsWave Motion and Waves on a String
A string of length 20 cm and linear mass density 0.40 g cm ⁻¹ is fixed at both ends and maintained under a tension of 16 N . At t = 0 , a wave pulse is created near one end, as shown in the figure, and travels towards the other end. At what time will the string again exhibit the shape shown in the figure?
Options
- A0.02 s
- B0.04 s
- C0.01 s
- D0.001 s
Correct answer
A. 0.02 s
Step-by-step solution
Given, length of the string, L = 20 cm = 0.2 m Linear mass density, = 0.40 g cm ⁻¹ = 0.40 10⁻³ kg 10⁻² m = 0.04 kg m ⁻¹ Tension in the string, T = 16 N The speed of the transverse wave pulse on the string is given by: v = T = 16 0.04 = 400 = 20 m s ⁻¹ For the string to again exhibit the exact same shape (an upright pulse traveling towards the right), the pulse must undergo two reflections. 1. It travels to the right end, reflects, and becomes inverted (since the end is fixed). 2. It travels back to the left end, re