Question

A ball is projected upwards from the ground with an
initial speed u. The ball is at a height of 160 m twice
within the time interval of 4 s, then initial speed u is
(1) 20 m/s
(2) 40 m/s
(3) 60 m/s
(4) 80 m/s​

Answer 1

u = 60 m/s is correct answer.