# Conservation of Momentum Question Involving Two-Dimensions

1. Sep 22, 2014

### omgbeandip

1. The problem statement, all variables and given/known data
A grenade is rolling due west at 0.954m/s along a floor when it explodes into three pieces of equal mass. The first piece moves at 3.6m/s, 20° [N of W]. The second travels at 5.8m/s, 62° [S of W]. Calculate the velocity of the third piece.

2. Relevant equations
P=mv
PBefore=Pafter
a^2 + b^2= c^2
Tan^-1 to find angle

3. The attempt at a solution
My attempt is in the attached image. I was curious if my masses were correct. Since they are all equal, I inputted 1 as my before component, and 1/3 for the 3 after components. Is this correct? And, are my calculations correct as well?

#### Attached Files:

• ###### Scan.jpeg
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2. Sep 22, 2014

### Orodruin

Staff Emeritus
Regarding the masses: You could simply assume that the grenade has a total mass $m$, which will make the parts have mass $m/3$. You will notice that $m$ cancels out of the final answer and thus that it does not matter what you chose for $m$. In particular, $m = 1\,\rm kg$ should give the correct answer just as well as any other mass.