Question

A ball is placed at the top of a hill and then released. After 5 seconds it has a speed of 20 m/s. What is the average acceleration of the ball? A) 10 m/s^2 B) 0 m/s^2 C) 100 m D)5 m/s^2 E) 4 m/s^2

Answer 1

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:

                                          v=u + at

                                          20 m/s=0 + a×(5second)

                                        a=(20/5) m/s²

                                                          a= 4 m/s²    (Ans)

So the option (E) is correct.