# To study the extension-load characteristics of a bicycle valve tube

## Objective

To study the extension-load characteristics of a bicycle valve tube.

## Introduction

For a linear spring described in textbooks, the extension is proportional to the applied force. But most materials are linear for a small extension range only. In this experiment you will study the relation between the load applied on a hanging bicycle valve tube and its extension. Also rubber shows hysteresis so the extension depends not only on the force but also on the history of stretching.

## Apparatus

bicycle valve tube with knots at the ends, a stand to suspend the tube, a weight hanger, weights, meter scale vertically fixed, graph paper etc.

## Procedure

Measure the natural length of the tube. Suspend the tube in the stand and the weight hanger from its lower end. Put the weights one by one and note the reading of appropriate point on the scale. Each time write the load and the scale reading in a table. Calculate the extension. Once you have gone up to say 1 kg, remove the weights one by one and each time note the extension. Write in the same table. Make sure you monotonically increase the load and also monotonically decrease the load. Also you have to give sufficient time after putting or removing the load for the tube to settle down.

Draw a graph with load on the \(x\)-axis and extension on the other axis. The area under the curve gives the work done by the load. Calculate the work done in the increasing load cycle and also in the decreasing load cycle. Your answer should be in joules. Is any of the two positive? Is any of the two negative? What is the total energy dissipated in the whole process?