# 2+ unknowns

1. Nov 28, 2004

### Warwick

Well, my physics teacher loves to make his problems hard, so he makes the physics portion of the problem med difficulty but he makes it so you have to solve with more than 1 unknown present. With big problems on forces I get lost in the algebra so.. i'm trying to improve my algebra skills. If anyone could give a couple algebra problems with 2 unknowns and solve for both, I would be grateful. Give me some nasty ones :)

I was making one up my self and couldn't figure it out.
8=2(2^2)
8=x(k^2)
I tired solving that but I couldn't get the answer, :yuck:

thanks

Last edited: Nov 28, 2004
2. Nov 28, 2004

### Nylex

If you have more than 1 unknown, you need more than 1 equation, unless you want one unknown in terms of the others.

8 = xk^2 => k = (8/x)^1/2

It is impossible to get k (or x) with such little info.

3. Nov 28, 2004

### marlon

4. Nov 28, 2004

### Warwick

Hmm, yes I remember doing these(not how, heh), never understood the use of them then. So this will work when I have 3 sum of the forces equations in physics when there is more than one unknown?

Can you show me how you would go about solving this one?

u=.065,m=2.5,a=0.12,g=9.8

Tcos20-ukn-mgsin25=ma
n-mgcos25+Tsin20=0

Well this one has only 1 unknown but can you use that matrice technique on it?

5. Nov 28, 2004

### marlon

not necessary, you only need the first equation.

ukn = -ma -mdsin25 + Tcos20

that's all

regards
marlon