# What's wrong with my calculation?

1. Nov 22, 2004

### scilover89

"If a particle which has mass travel at the speed of light, the particle mass will reach infinity, which require infinity energy to move it, thus particle can't travel beyond the speed of light."
I made an calculation about it.(And it turned out to be wrong) However, I couldn't find the mistake!
This is my calculation:
Let the mass = 1kg, and the velotion = c
Kinetic energy gained while travelling=0.5mc^2
=0.5c^2
When these energy is fully converted into mass,
Einstein's Equation:E=mc^2
0.5c^2=mc^2
m=0.5
The mass gained by the particle is 0.5, not infinity? Why?

2. Nov 22, 2004

### vsage

Last edited by a moderator: Nov 22, 2004
3. Nov 22, 2004

### Staff: Mentor

That equation describes the amount of energy released when turning mass into energy - it has nothing to do with relativistic mass.

4. Nov 22, 2004

### marlon

and besides m = 1kg is nonsense because you are confusing rest-mass and relativistic mass. Keep in mind that mass is always interpreted as rest-mass though the epitheton rest is left behind...

marlon