When the ball is released from the top of the hill then
it's initial velocity (u)=0
And it's final velocity will be after 5 second (v)=20
m/s
Now to calculate the acceleration we need to use
Newton's first law os motion:
                                        Â
v=u + at
                                        Â
20 m/s=0 + a×(5second)
                                      Â
a=(20/5) m/s2
                                                        Â
a= 4 m/s2Â Â Â (Ans)
So the option (E) is correct.
