We use the equation of motion,
[tex]v=u+at[/tex]
Here, v is final velocity, u is initial velocity, t is time taken and a is acceleration.
Given, [tex]v= 6.34\times10^5 m/s, u=4.2 \times10^5 m/s[/tex] and [tex]a = 1.9 \times10^4 m/s^2[/tex] .
Substituting these values in above equation , we get
[tex]6.34\times10^5 m/s=4.2 \times10^5 m/s+1.9 \times10^4 m/s\times t \\\\t=\frac{2.14 \times10^5 m/s}{1.9 \times10^4 m/s^2} =11.2\ s[/tex]
Therefore, time taken by an electron to reach the given final speed is 11.2 s.
