Velocity of Particles

Submitted by mhk on Tue, 11/12/2013 - 06:38

Hi everyone,
I have tried to calculate the velocity of particles based on their position, but the results show that the velocities which I calculated are exactly twice the dumped velocity. I have checked the time interval, I used the real time as follows:
"real time=timestep*No. of steps"
I was wondering if anyone has any idea why this happens?or what am I doing wrong?