1. The problem statement, all variables and given/known data "If a rock is thrown upward on the planet Mars with a velocity of 10 m/s, its height (in meters) after t seconds is given by H = 10t - 1.86t^2." a) Find the velocity of the rock when t = a b) Find the velocity of the rock after 1 second c) When will the rock hit the surface? d) With what velocity will the rock hit the surface? 3. The attempt at a solution I was able to do parts a and b. Im stuck at c and d though. For (a) I derived the formula that is given. Which turns to: 10 - 3.72a For (b) I substituted 1 into the equation which gives: 6.28 Now how would I go about finding out when the rock will hit the surface and it's velocity? Any help appreciated.