question_answer 50)

                  A ball is thrown from a roof top at an angle of \[{{45}^{o}}\] above the horizontal. It hits the ground a few seconds later. At what point during its motion, does the ball have                 (a) greatest speed           (b) smallest speed                 (c) greatest acceleration ? Explain

Answer:

                  (a) When the ball just reaches the ground. (b) At highest point, speed of ball = horizontal component of velocity \[=\upsilon \cos {{45}^{o}}=\frac{u}{\sqrt{2}}\] and the vertical component is zero. Therefore, ball has the smallest speed at the highest point. (c) The ball moves with constant acceleration through its journey and this constant acceleration = g.