Question

Plz explain Question 53..

Answer 1

Ans. is (-5)m/s^2 .. solution is in the pic :)

Answer 2

first you will need to draw the graph of v-t.as given above.With values of v .
then make graph for acceleration time.
it will zero everywhere except in middle where velocity is changing.from change in velocity 20 to 0 it will at a instinct so average acceleration=total change in velocity/total time.
a={20-(-20)}/(8-0)=40/8=5.