Calculate the velocity and kinetic energy of a neutron (mass 1.675x10-27kg) that has a wavelength of 0.2nm. How does this compare to the average kinetic energy of a gas molecule at room temperature (0.038eV at 200C)? 1. E=mc^2 2. KE = 1/2 mv^2 I used 1. to calculate the energy which was 1.51 x10^-10 J Then i subbed the energy into 2. and got a velocity of 4.24 x10^8 m/s LOL obviously i'm going wrong some where how can a neutron be going faster than light! CAN SOMEONE HELP PLEASE?