an 80 kg boy holding on to a helium balloon jumps off of a 20m tall building and floats to the ground. If the boant force of the balloon is 750 N upward, what is the boy's acceleration and final velocity just before he touches the ground?
80x10-750 =80a
50=80a
acceleration a =5/8
V ssquared = u squared + 2as
= 2x 5/8 x 20
= 25
V= m/s