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**Problem statement**

How fast must a neutron be travelling relative to a detector in order to have a measured kinetic energy that is equal to its rest energy?

**An "attempt"**

I know

Ek = mc^2 - m0c^2

But if Ek = m0c^2, wouldn't the two terms cancel out from this equation? I am having trouble going about with it mathematically, and could use a few pointers if you guys don't mind helping out.

Where m0 is the rest mass.

m is the relativistic mass