# Math Help - Work

1. ## Work

A force of 7 pounds compresses a 15 inch spring a total of 4 inches. How much work is done in compressing the spring another 3 inches?

2. Originally Posted by CalcGeek31
A force of 7 pounds compresses a 15 inch spring a total of 4 inches. How much work is done in compressing the spring another 3 inches?
use Hooke's law, $F = kx$ , ... find the spring constant $k$

$W = \int_4^7 kx \, dx$

3. Set the 0 to be at 15 the natural length of the spring

F = kx

7 = 4k

so k = 7/4

F = (7/4)x

W = integral [from -4 to -7 of (7/4)xdx]