# Calculate velocity of a 1MeV Neutron

1. Aug 26, 2014

### rem45

How would one calculate the velocity of a 1MeV neutron??

I tried the following the attached formula for V/C but E is less than the rest mass which yields the square root of a negative number. Not sure what to do for this

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2. Aug 26, 2014

### Staff: Mentor

1 MeV here is surely the kinetic energy, not the total (rest plus kinetic) energy.

3. Aug 26, 2014

### rem45

It doesn't say. I guess that I will assume such. Is the 'E' in the equation I am using for the rest mass energy plus the kinetic energy?

4. Aug 26, 2014

### Matterwave

Since a neutron has a higher rest mass than 1MeV, then one should safely assume that kinetic energy is what is meant here.

The E in that equation is indeed the rest+kinetic energy.

5. Aug 27, 2014

### mathman

Since the neutron rest mass is approximately 940 Mev, you probably could use E=(mv^2)/2 to get v. (v=c/22?).

Last edited: Aug 27, 2014
6. Aug 27, 2014

### Staff: Mentor

I agree that a nonrelativistic approach should be fine - it is a very good approximation.