A car is moving down a flat, horizontal highway at a constant speed of 21.0m/s when suddenly a rock dropped from rest straight down from an overpass crashes through the windshield. The rock strikes the windshield at a right angle, and the windshield makes a 60º angle with the horizontal.
a. Find the speed of the rock relative to the car when it hits the windshield.
b. Find the distance above the point of contact with the windshield from which the rock was dropped.
c. If the driver had seen what was about to happen just as the rock was being released, how much time would she have had to react before the rock strikes the windshield?