Question

A tuning fork is in resonance with a vibrating string under tension. When the tuning fork is moved with a certain velocity, 2 beats per second are heard. If the tension is increased, the beats disappear again. The direction of motion of the tuning fork is

• A. towards the string
• B. away from the string
• C. random
• D. unpredictable as data is not sufficient

Answer 1

Answer: (A)

When tension is increased the frequency of the string increases from $n$ to $n+\Delta n$ . This means apparent frequency of the tuning fork has also increased from $n$ to $\left(n+\Delta n\right)$ . So the tuning fork is moving towards the string.