2.17 x [tex]{10}^{-3}[/tex] is the ratio of the kinetic energy of the hydrogen atom after the collision to that of the electron before the collision.
As we know that there is no external force on the system of hydrogen atom and electron so we will say momentum is conserved.
so we will have
[tex]m_1v_{1i} =m_1v_{1f} +m_2v_{2f}[/tex]
here we know that
[tex]m_1=m[/tex]
[tex]m_2=1837m[/tex]
now we have
[tex]m_1v_{1i} =mv_{1f} +1837mv_{2f}[/tex]
[tex]v =v_{1f} +1837v_{2f}[/tex]
Also we know that
[tex]v_{2f} -v_{1f} =v[/tex]
Now we will have
[tex]\frac{v}{919} =v_{2f}[/tex]
now we need to find the ratio of the kinetic energy of hydrogen atom with initial kinetic energy
so it is given as
[tex]\frac{K_h}{K_i} =\frac{1837}{919 X 919}[/tex]
[tex]\frac{K_h}{K_i} = 2.17 X {10}^-3[/tex]
Hence, 2.17 x[tex]{10}^{-3}[/tex] is the ratio of the kinetic energy of the hydrogen atom after the collision to that of the electron before the collision.
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