On Mon, May 25, 2015 at 5:18 AM, <doris...@berkeley.edu> wrote:
> Hi all,
>
> I am new to SymPy and I am trying to rearrange equations in order to express
> one variable in terms of another in SymPy.
> For example, I have two physics equations F=ma and rho=m/v which I defined
> in the beginning. I want to re-express ``a`` in terms of f,rho, and v.
> However, the ``solve`` function sets the right hand side of the equation so
> that it is equal to zero so then when I try to get ``a`` in terms of `f` it
> returns zero.
> Is there a way I could do this SymPy, if so, which function should I be
> looking at instead?
Is this what you want?
First find m in terms of F and a:
>>> m1 = solve(F-m*a, m, dict=True)[0][m]
Now, feed in above to the second equation:
>>> solve(rho - m1/v, a)
[F/(rho*v)]
Best,
Amit.
>
> Thank you.
>
>
>
> In [6]:
>
> from sympy import *
>
> In [11]:
>
> f = Symbol('f')
>
> m = Symbol('m')
>
> a = Symbol('a')
>
> rho = Symbol('rho')
>
> v = Symbol('v')
>
> In [37]:
>
> f=m*a
>
> rho=m*v
>
> In [38]:
>
> solve(a,[f])
>
> Out[38]:
>
> []
>
> In [39]:
>
> solve(rho,[v])
>
> Out[39]:
>
> [0]
>
> In [42]:
>
> solve_linear(f-m*a,f)
>
> Out[42]:
>
> (m, 0)
>
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