21)
a) The furthest point is when t=40s Look at the graph...after 40s, it remains where it is for another 10s...then it starts moving back...negative velocity indicates opp direction...so it's going back where it started from 50s onwards
b) a=v-u/t = 2/30=1/15 m/s2
c) from 0<t<40, it travels 30X3 + 5X3= 105m (area under the graph)
from 50<t<120, it travels 1/2 X (120-50) X2 = 70m ( area under the graph) --> this is in the opp direction....displacement is -70m
therefore the distance from A is 105m-70m=35m
