# K=1/2mv^2 simple physics question

1. Feb 22, 2015

### Westin

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

A ball whose mass is 8kg travels at a velocity [PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char68.png22,79,6[PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmsy10/alpha/144/char69.pngm[PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmmi10/alpha/144/char3D.pngs. [Broken] What is the rest energy of the ball?

2. Relevant equations

K=1/2 mv^2

3. The attempt at a solution

K=1/2 (8) v^2

Im not sure what to do with velocity since its in vector form, I tried taking the magnitude of it but that was incorrect.

Last edited by a moderator: May 7, 2017
2. Feb 22, 2015

### SteamKing

Staff Emeritus
The problem is asking for the 'rest energy' of the ball. I don't think you need to know the velocity of the ball in order to calculate its rest energy.

Last edited by a moderator: May 7, 2017
3. Feb 23, 2015

### haruspex

Unless the mass given is based on the speed given, but it's a speed so subluminal the difference will be minute.