A. For the first questions, it asked for the
speed of the rocket when it goes down. A stands for speed so you add the upward
speed of 30 then slows down by 10 when it goes down so
a=30+10=40m/s2
B. This refer to speed of the rocket as it goes down
so with the formula
V = u +at
V = 402 = 80m/s
Then solve for S
S = ut + ½^2
S = 1/2 40 22 = 80m
C. At t=0, the rocket is at rest.