Physics 9702/52 — February/March 2018

A student is investigating how the extension $e$ of an elastic cord depends on the diameter $d$ of the cord when a force is applied.

The student has a number of elastic cords of the same material with different diameters. The elastic cords have circular cross-sections. Each cord has an unstretched length of approximately $50\text{ cm}$.

It is suggested that the extension $e$ and the cross-sectional area $A$ of the cord are related by the expression

where $E$ is the Young modulus of the material of the cord, $F$ is the force applied and $L$ is the unstretched length of the cord.

Design a laboratory experiment to test the relationship between $e$ and $d$.
Explain how your results could be used to determine a value for $E$.

You should draw a diagram, on page 3, showing the arrangement of your equipment. In your account you should pay particular attention to

• the procedure to be followed,
• the measurements to be taken,
• the control of variables,
• the analysis of the data,
• any safety precautions to be taken.