A student throws a set of keys vertically upward to his fraternity brother, who is in a window 3.95 m above. The brother's outstretched hand catches the keys 1.80 s later. (a) With what initial velocity were the keys thrown?

Answer 1

d = Vo*t + 4.9t^2 = 3.95m,
Vo*1.8 + (-4.9)(1.8)^2 = 3.95,
1.8Vo - 15.876 = 3.95,
1.8Vo = 3.95 + 15.876 = 19.826,
Vo = 11m/s.