A body rises vertically from the earth according to the law s = 64t – 16t2. If it has lost k times its velocity in its 48 ft rise, then k =

V^2 = Vo^2 + 2g*h.

V^2 = 64^2 - 64*48 = 1024
V = 32 ft./s.

64 - 32 = 32 ft./s = Velocity lost.

32 = k * 64.
k = 0.5.