This is an annoying problem for which I have a close answer to, not sure where I went wrong.(adsbygoogle = window.adsbygoogle || []).push({});

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

Cannonball Man (mass = 75kg) is stuff into his circus cannon, compressing a giant spring by 1.5 meters. He is launched vertically upward at 5 m/s reaching a maximum height above the circus floor of 10 meters. What is the spring constant of the spring?

2. Relevant equations

Conservation of Energy "Master Equation," as I like to call it:

(1/2mv^2 + mgh + 1/2kx^2)initial = (1/2mv^2 + mgh + 1/2kx^2)final

Where k = the spring constant

x = compression/extention of spring

h = the change in height

3. The attempt at a solution

I think I went wrong with the final and initial velocities, but I'm not sure specifically where my error was. First I cancelled stuff:

(0 + mgh + 0)initial = (1/2mv^2 + 0 + 1/2kx^2)final

Then I plugged in my variables

(75)(9.8)(10) = (0.5)(75)(5^2) + (0.5)k(1.5^2)

And solved for k: 5700 N/m

All I know for sure is that I'm relatively close to what my answer should be; I recieved 17/20 for my entire submission (this was an old written assignment; I have no way of checking for the actual complete answer).

Can someone help me out please?

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Work and Energy Problem

**Physics Forums | Science Articles, Homework Help, Discussion**