Let's say there is no gravity here and objects won't crush. We have 2 rocks with $m=10\text{ kg}$. First rock has velocity $v_1=0\text{ m/s}$ and second $v_2=10\text{ m/s}$ (flying in leftward direction). The second rock hit first causing force for a time $t=0.001\text{ s}$.

$F=ma \rightarrow F=\frac{mv}{t} \rightarrow F=\frac{10*10}{0.001} = 100000\text{ N}$

$a=F/m= 100 000/10 = 10 000\text{ m/s}^2$

So acceleration is $10 000\text{ m/s}^2$ in time $0.001\text{ s}$ meaning change in velocity would be $10\text{ m/s}$? It would mean first rock would travel at velocity $10\text{ m/s}$ (flying in leftward direction) and the second would stop $(10-10=0)$ but it seems against all logic.

I probably messed up something here so anyone can help?