1. The problem statement, all variables and given/known data Gwen releases a rock at rest from the top of a 40 m tower. If g = 9.8 m/s2 and air resistance is negligible, what is the speed of the rock as it hits the ground? v0 = initial velocity = 0 a = acceleration = 9.8 Δy = displacement in y direction = -40 v = final velocity = ? 2. Relevant equations v2 = v02 + 2aΔy 3. The attempt at a solution v2 = v02 + 2aΔy v2 = 0 + 2 (9.8) (-40) v2 = -784 but v2 can't be a negative number. I'm guessing either delta y is not supposed to be negative, but I thought it should be since the rock is falling, not being thrown upwards, or gravity should be negative, but I thought that when motion is downwards, the acceleration due to gravity should be positive.