An electron and a proton are detected in a cosmic ray experiment . Both of them have kinetic energy 100 keV. Which one is faster ?

Explanation

Kinetic energy , `K=1/2 mv^2,i.e., v=sqrt((2K)/m)`
For the same kinetic energy `v prop 1/sqrt(m)`.
The mass o fan electron is less than that of a proton. So, the electron has higher velocity, i.e., the electron is faster.