Question

You are at standing at a window in the University tower that is 42.0 meter above the ground. Your physics professor (who is 2.12 m tall) is walking on the ground below, approaching to tower at a speed of 1.12 m/s. You are holding an egg, which you would like to drop on your professor's head. If you drop the egg from rest, how far in advance of the tower should your professor be (in distance) at the instant of release such that the egg hits him directly on the head as he passes below the window?

Answer 1

How long to drop 42 - 2.12 = 39.88 meters?

h = Hi + Vi t + (1/2) a t^2
0 = 39.88 + 0 - 4.9 t^2

t^2 = 39.88/4.9
so
t = 2.85 seconds
how far does he walk in 2.85 seconds?
d = 1.12 * 2.85 = 3.2 meters