Equations solving on Matlab , 3 unkowns and 2 equations.

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Rana Önem
Rana Önem 2020-5-29
评论： Rana Önem 2020-5-29
v0=vf+ vfg*x;
u0=uf+ufg*x;
If we know vf,vfg,uf,ufg values how can I calculate x? Can you help me please?
Also there is this eq. m2*(he-u0)==m1*(he-u1); , we know he, m1,u1, values too.
In addition this eq. m2=v/vO; we know v value.
  2 个评论
Robin Kirsch
Robin Kirsch 2020-5-29
编辑：Robin Kirsch 2020-5-29
if you have the 2 formulas m2 *(he... and m2 = v/v0 , dont you have 3 unknowns and 3 equations then? see my answer below
or is v0 of the first equation different from the m2 = v/vO?

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回答（1 个）

Robin Kirsch
Robin Kirsch 2020-5-29
If you simply want to know x, v0 and u0 you can just use the solve method. I assumed random variables for the known constants in my example.
syms x v0 u0
vf = 3;
vfg = 5;
uf = 2;
ufg = 1;
v = 7;
he = 2.5;
m1 = 4;
u1 = 1.1;;
eqn1 = v0 == vf+ vfg*x;
eqn2 = u0 == uf+ufg*x;
eqn3 = v/v0 * (he - u0) == m1*(he-u1);
[x v0 u0] = solve([eqn1, eqn2, eqn3], [x, v0, u0])
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Brent Kostich
Brent Kostich 2020-5-29
If you use 'syms' you get symbolic variables. They do not produce a numeric output. You can substitute numeric values for the syms to get a numeric output.
https://www.mathworks.com/help/symbolic/subs.html
https://www.mathworks.com/help/symbolic/symfun.html

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