4) A skater begins skating from rest and accelerates at a rate of 3 m/s2 for 5 seconds. What is her final velocity?

15 m/s

Explanation:

initial velocity:0 m/s ( rest)

acceleration:3m/s²

time taken : 5 sec

final velocity: ?

a = v-u/t

3 = v-0/5

15 = v-0

15 +0=v

therefore, v=15 m/s

one "light year" is the distance that light travels, through vacuum, in one julian year.   that's 365.25 days, of 24 hours each.