Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Holding a Node in a Vibrating String

Introduction

If a string tied at both ends is vibrated at one of its natural frequencies, it forms nodes and antinodes. At nodes, the string does not vibrate at all. But still if you hold it, it affects the loop formation on the string as will be demonstrated in this experiment.

Apparatus

Vibrator, function generator, string 100-150cm, a fixed support.

Procedure

  1. Tie one end of the string to the vibrator and the other end to the fixed support. The string should only be slightly tight.
  2. Connect the output voltage of the function generator to the vibrator. Put on the function generator, keep amplitude maximum.
  3. Adjust the frequency to form 4-5 loops on the string.
  4. Gently touch a node from below and slightly press it up.
  5. Question: What happens to the vibrations beyond the node held?
  6. Question: What happens to the vibrations before the node held?