A-level Physics (Advancing Physics)/Fission/Worked Solutions

1. A neutron is fired at some Uranium-235. Barium-141 and Krypton-92 are produced:

How many neutrons are produced (i.e. what is the value of N)?

Consider the mass numbers:

2. What proportion of the neutrons produced must be absorbed in order to make the reaction stable?

Two thirds, assuming that Uranium-235 always produces three neutrons when split, which it doesn't.

3. What would happen if too many neutrons were absorbed?

The reaction would stop.

4. Alternatively, Uranium-235 can split into Xenon-140, two neutrons and another element. What is this element? (You will need to use a periodic table.)

Consider the mass numbers:

Then consider the atomic numbers:

So, the element is strontium-94: