# C = √ (E/m) We can determine c !

1. Mar 11, 2013

### ebodet18

If this is true why can't we just find an energy divided by a very small mass, square root it and thats what the speed of light equals for that object?

2. Mar 11, 2013

### Jorriss

We can not because $c^{2}$ is the proportionality constant between mass and energy. One can not just find mass and energy in any ratio.

Last edited: Mar 11, 2013
3. Mar 11, 2013

### Staff: Mentor

No problem. Just tell us how you would go about accurately measuring the amount of energy in the mass.

4. Mar 11, 2013

### PAllen

Let's have fun with this. Weigh a small mass in a known gravitational field; you've got m. Inject slowly (vanishing KE) into an anti-calorimeter; you've got 2E.

You can buy anti-calorimeters from the same store that sells 1 light year Born rigid rods, frictionless surfaces, rigid massless shells, etc.