Physics (AS & A Level) · Feb / March 2025 · Paper 12 · Question 38

A stationary nucleus has nucleon number A. The nucleus decays by emitting a proton with speed v to form a new nucleus with speed u. The new nucleus and the proton move away from one another in opposite directions. Which equation gives v in terms of A and u?

1. Av = (A/4 − 1)u
2. Bv = (A − 1)u
3. Cv = Au
4. Dv = (A + 1)u

As printed in the paper