physics problem help??

Question

A ball is tossed from a flat ground with UNKNOWN initial velocity V0. There is no air resistance. The total time of flight (time up +time down ) ball spends in air is 16 seconds. The initial velocity of the ball is V0 = ______ m/s

A) 160

B) 40

C) 80

D) 1.6

Answer 1

Let t = time for one way flight

T = 16 sec

t= T/2 = 8sec ( Symmetry of motion up and down)

for up motion Vf=0

Vi= ?

Vf= Vi - gt , Using g= 9.8m/s2

0 = Vi -9.8 t

0 = Vi - 9.8 *8

Vi = 9.8*8 = 78.4m/s

Closest to C)