- #1

vinnyzwrx

- 15

- 0

## Homework Statement

At a certain point, when a spring is stretched near its elastic limit, the spring force satisfies the equation

F = −α x + β x3 , where α = 12 N/m and β = 890 N/m3 .

Calculate the work done by the spring when it is stretched from its equilibrium position to 0.15 m past its equilibrium.

Answer in units of mJ.

## Homework Equations

## The Attempt at a Solution

since this is a nonlinear curve i thought that the area under the curve would equal the work done by the spring at the .15 m

so i integrated and got

-6x

^{2}+ 222.5x

^{4}

since the spring is starting at the equilibrium position, initial position is 0 and final position is .15m so

-6(.15)

^{2}+222.5(.15)

^{4}= -.02235

this doesn't make sense since we are pulling the spring and the work should be positive right?