# Homework Help: Multiple Answers stored in matrix?

1. Jul 23, 2011

### GreenPrint

If
KE=(m V^2)/2
Then
V=matrix([[(2^(1/2)*KE^(1/2))/m^(1/2)], [-(2^(1/2)*KE^(1/2))/m^(1/2)]])
Would this notation be considered improper?
I'm just wondering because this is what my computer printed out.
or something like this
V=matrix([-5],[5]) m/s
Is this acceptable?

2. Jul 23, 2011

### SammyS

Staff Emeritus
Solve the equation, KE=(m V2)/2, for V, using algebra. You should get two solutions. That's all your calculator is telling you.

Now, is V velocity or is it speed, in your equation?

3. Jul 23, 2011

### GreenPrint

Ya I'm completely aware that there are two solutions and that V is a vector velocity. I'm just asking if this is proper notation and if it's ok for me to leave my results like this, that is all. I don't see why it would not be ok for me to leave my results like this. I just have never seen anyone set solutions equal to a matrix if there are multiple solutions and don't know how it would be received by my professors if I leave my results like this. I don't don't see why not, but I just wanted to make sure.

4. Jul 23, 2011

### SammyS

Staff Emeritus
How would you write the solution if you did it by hand?

5. Jul 23, 2011

### GreenPrint

Not given any context on the problem I can't determine the direction of the velocity. So I would write it like

V = +/- 5 m/s

but I guess if there were more than two solutions, in this case there wouldn't be, but like if I was solving a equation and get something like
x=4
x=5
x=6
I would write it like
x=4,5,6

6. Jul 23, 2011

### SammyS

Staff Emeritus
So, I would write my answer like either of those, not as a matrix.

7. Jul 23, 2011

### GreenPrint

Ya I would to. That's why I question if it's proper or not to leave my answers like this. Given that there can only be one answer in a certain situation and your given multiple I feel as if it's improper to write
x= 4 or 5 or 6
to indicate that it can only be one of those solutions
that's why I think this would be better to write it like this if they represent the same things
x=[4 5 6]
not sure if it would be understood as representing the same things
like could someone say that doing so is incorrect or wrong because
x= 4 or 5 or 6
implies something different than
x=[4 5 6]
?