1. The problem statement, all variables and given/known data A boy at the top of a roller coaster falls through a vertical distance of 20m. What is the final speed of the boy if: a) His initial speed was 0 b) His initial speed was 5 ms-1 2. Relevant equations GPE at top = KE at bottom mgh = 1/2mv^2 gh = 1/2v^2 v = √2gh if the initial velocity (u) was not equal to zero, the maths becomes slightly different initial total energy = final total energy 1/2mu^2 + mgh = 1/2mv^2 therefore.... v^2 = u^2 + 2gh 3. The attempt at a solution a) 2x9.8x20 = 392 b) 5^2 + 2x9.8x20 = 417 The answers are: a) 19.8 ms-1 b) 20.4 ms-1 What on Earth am I doing wrong... what can I do... or what!?! D: I just don't understand!!!