1. The problem statement, all variables and given/known data Hi, need some help trying to understand calculus derivation of the rocket equation. If someone who be so kind as to look at the attachment where it is all laid out. 2. Relevant equations All equations are listed in the attachment 3. The attempt at a solution I have had a good go at this and understand all the derivatives and integrations just not the subtle details. I don't get how you can swap all the deltas for d's towards the end of the derivation. From the research I have done on the web, delta m (mass) is not the same as dm so how can you suddenly change from deltas to d's? For example the mass starts off as delta m, then goes to dm and then disappears! Also what is the reason for suddenly integrating both sides of the equation right at the end? I understand why you take the derivative as this gives you the force (dp/dt) but why then integrate the velocity on the left then the mass on the right? Thank you for any guidance given!