# Homework Help: How far does a block travel before hitting a spring?

1. Nov 20, 2013

### oneamp

1. The problem statement, all variables and given/known data
A block starts from rest at the top of a 31.0 degree inclined plane and encounters a spring, of constant 3.4 kN/m, rigidly attached to the plane. If the block's mass is 33.0 kg and it compresses the spring by 37.0 cm, find the distance the block travelled before it encountered the spring.

2. Relevant equations

3. The attempt at a solution

The spring compresses to 37cm, and has a spring constant of 3,400 kN. So I solve for U_s, the potential energy of the spring, and get U_s = 232.73 J.

Since friction is not mentioned, I know that the potential energy at the top of the incline equals U_s. Or, mgy = 232.73J, or (33)(9.8)y = 232.73. I use trig and solve for the distance travelled, but it doesn't match the answer of the problem. What am I doing wrong?

Thank you

2. Nov 20, 2013

### Staff: Mentor

When you solved for the distanced traveled, did you take into consideration the 37 cm? (They want the distance traveled before hitting the spring.)

3. Nov 20, 2013

### oneamp

That's it. Thank you