# If someone can help me with the correct equation to use, I would be gratly obliged!

1. Nov 18, 2009

### yomama

A 55kg skateboarder wants to make it to the upper edge of a quarter pipe with a radius 3.0 m. What speed do they need at the the bottom?
A.) 7.7 m/s
B.) 9.1 m/s
C.) 5.4 m/s

If you could help me out with the correct formula to use, that would help!!!!

2. Nov 18, 2009

### yomama

Re: If someone can help me with the correct equation to use, I would be gratly oblige

Sorry new to the site... Revised the question on a later post

3. Nov 19, 2009

### donhubix

Re: If someone can help me with the correct equation to use, I would be gratly oblige

Hello Yomama

This can be done very quickly and effectivelly with the assistance of two energy equations:

Potential energy=mgh
Kinetinc Energy=(mv^2)/2

Equate the two in the following way:

mgh=(mv^2)/2 Note: m cancelles out

gh=(v^2)/2
2gh=v^2
v=sqrt(2gh) where: g=9.81, h=radius of pipe=3

Find v by substituting the value.

Hubert