by applying Heisenberg's uncertainity principle

if we assume the electron to be inside the nucleus and calculate its velocity inside the nucleus it comes out to b more than the vel of light which is not possible. so it cannot exist inside the nucleus

 

we calc the vel of electron in the foll way:

as e^- is assumed inside the nucleus delta x = 10^-15m

the product delta x. delta v = h/(4. pi. m)

therefore delta v = h/(4. pi. m. delta x)

subs the values of h, pi, m and delta x to get the ans as 5.8 x 10¹⁰m/s