A ball is thrown horizontally towards a wall.Given that the ball needs 0.5s to reach the wall and the distance between the original position of the ball and the wall is 20m.
Find the speed of the ball when it reach the ball.
Assume that the speed of the ball is constant when it travels.
I use
s=1/2(u+v)t
20=1/2(v)(0.5)
v=80 ms-1
when I use
v=s/t
v=20/0.5
v=40 ms-1
Why different answers are obtained in my calculation?