1. The problem statement, all variables and given/known data A radium nucleus decays by emitting an alpha particle. The speed of the recoiling nucleus is small compared to the speed of the alpha particle. This is because the: A force acting on the recoiling nucleus is smaller than the force acting on the alpha particle B momentum is mainly concentrated in the alpha particle C momentum of the recoiling nucleus is smaller than the momentum of the alpha particle D recoiling nucleus has a much larger mass than the alpha particle why is it D? http://www.edexcel.com/migrationdoc...E January 2010 - ER/6PH04_01_pef_20100310.pdf Look at question 7) for part (i) why is it C and for part (iii) we were NOT told that O was stationairy so why is it D? 2. Relevant equations 3. The attempt at a solution ok so for q3) there is no way to conclude any of them A: we don't know the accelerations B: how much faster is it moving? C: again we don;t know exact speeds D: true but why relevant? for Q7) i) I would have said none of them can be KNOWN but I would say X and Y have the same charge as they move in the same direction ii) I got iii) we are not told if O is stationairy or not?