10. A rock is thrown upwards from the top of a 45 m tall cliff with an initial speed of 15 m/s. (a) What is the maximum height reached by the rock? (b) For what total time is the rock in the air before it strikes the ground at the base of the cliff?
h(t) = 45 + 15t - 4.9t^2
(a) max height is when t = 15/9.8
(b) solve for t when h=0