# Homework Help: Stress and Strain, simple question! Just need a clarification

1. Jun 11, 2009

### grandprix

1. The problem statement, all variables and given/known data

A tow truck is pulling a car out of a ditch by means of a steel cable that is 9.1 m long?
and has a radius of 0.50 cm .when the car just begins to ,move , the tension in the cable is 980 N. how much has the cable stretched?

Y steel= 2.0 x 10¹¹ N m²

2. Relevant equations

F/A = Y (delta L / L0 )

3. The attempt at a solution

We just need to solve for delta L, but I am having difficulty figuring out what A would be - any help? What A formula for the cable do I use?

2. Jun 11, 2009

### grandprix

nvermind I think I got it!

890/(2pi*r(in meters) = Y (delta L/9.1)

is this correct?

3. Jun 11, 2009

### rock.freak667

the A in the equation is area, the steel is circular to $A=\pi r^2$ and convert r to metres.

4. Jun 11, 2009

### grandprix

thanks so much!!