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

# Waves Motion in a Slinky

## Objective

To demonstrate that wave velocity depend on tension and mass density.

## Introduction

The velocity of a wave on string is given by $$v=\sqrt{T/\mu}$$, where $$T$$ is the tension in the wire and $$\mu$$ is its mass per unit length. A slinky, when stretched, offers a nice medium for demonstration of wave aspects. The number of turns per unit length acts for linear mass density and tension is the force by which each turn is pulled by its neighbour.

## Apparatus

Why did the speed increase? By stretching it further you have increased the tension and decreased the number of turns per unit length. Thus effective $$T$$ increased and effective $$\mu$$ decreased. Both these results in increase in wave speed according to the equation $$v=\sqrt{T/\mu}$$.