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A uniform string of length 20 m is suspended from a rigid support. A short wave pulse is introduced at its lowest end. It starts moving up the string. The time taken to reach the support is: (take g = 10 m s⁻²)

1. 2π√2 s
2. 2 s
3. 2√2 s
4. √2 s

Correct answer: 2√2 s

Solution

The speed of a wave on a string is determined by the tension and mass per unit length. For a uniform string, the wave speed can be calculated using the formula v = √(T/μ), where T is the tension and μ is the mass per unit length. Given the length of the string and the acceleration due to gravity, the time taken for the wave pulse to travel the entire length of the string is derived as 2√2 s.

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