- #1

mbrmbrg

- 496

- 2

The figure is a block resting on a horizontal surface, attatched to a horizontal spring.

-our force=spring force=-kd

so -89J=-k(-0.02m)==>k=-4450N/m

I then said that [tex]W=-(k\frac{x_f^2}{2}-k\frac{x_i^2}{2})[/tex], subbed in W=3.3 J, k=-4450N/m, x_i=-0.02m, and got the right answer (which is +/- 4.3cm).

But why did that equation work? 3.3 J is our work, not the spring's?