Thank you so much for taking the time to help me.
The change in Δd that you mentioned happened because I split the rock's motion into being thrown straight up (which is the part where final velocity is zero), and falling down to the ground from its maximum height (final velocity is not zero...
Homework Statement
Rock A is thrown straight up from the top of a 25m tall building at a speed of 20m/s. Exactly 1 second later Rock B is thrown in such a way that it lands on the ground at the base of the building at the same instant that Rock A lands. What is the initial velocity for Rock...