Large equations system in Wolfram Alpha is not understood

Questions
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1

Hi,
I have this system, and some known and unknow variables. I want to express the latter with known ones. The WolframAlpha main page form has length limit reached a bit before the end, so I’ve shortened the formula (rename variable), end then it says it does not understand.

Can you help me on this ?

The system:

E=dec1+dec2
dec1=ec_1-ec1
ec1=(1/2)*m1*v1^2
ec_1=(1/2)*m1*v_1^2
dec2=ec_2-ec2
ec2=(1/2)*m2*v2^2
ec_2=(1/2)*m1*v_2^2
dv1=v_1-v1
dv2=v_2-v2
m1*dv1=m2*dv2

Known:

m1,m2,E,v1,v2
ec1, ec2

trivial, considered known :

ec_1, ec_2, dec1, dec2, v_1, v_2, dv1, dv2

My 1st query, a bit too long:

Solve[{m1*dv1=m2*dv2,E=dec1+dec2,dec1=ec_1-ec1,ec1=(1/2)*m1*v1^2,ec_1=(1/2)*m1*v_1^2,dec2=ec_2-ec2,ec2=(1/2)*m2*v2^2,ec_2=(1/2)*m1*v_2^2,dv1=v_1-v1,dv2=v_2-v2,m1*dv1=m2*dv2},{ec_1,ec_2,dec1,dec2,v_1,v_2,dv1,dv2}]

The 2nd query: I replaced the “ec” by “k” in variable name.

Solve[{m1*dv1=m2*dv2,E=dk1+dk2,dk1=k_1-k1,k1=(1/2)*m1*v1^2,k_1=(1/2)*m1*v_1^2,dk2=k_2-k2,k2=(1/2)*m2*v2^2,k_2=(1/2)*m1*v_2^2,dv1=v_1-v1,dv2=v_2-v2,m1*dv1=m2*dv2},{k_1,k_2,dk1,dk2,v_1,v_2,dv1,dv2}]

But “Wolfram|Alpha doesn’t understand your query”. I’ve done it by hand, just wanted to see what Wolfram would answer. Thanks for any help.

2 
Solve[{m1*dv1=m2*dv2,E=dk1+dk2,dk1=k_1-k1,k1=.....

I do not use Alpha. But in Mathematica, you should not use “_” (underscore) in variable names. The “_” has special meaning in Mathematica (used for pattern). Also E is the exponential constant and can’t assign to it.