Question

(a) Jennifer holds a ball 1.5m above the ground. Daniel, laying out if a car window, also holds a ball 1.5m above the ground. Daniel drives past Jennifer af 40 mph and, just as he passes her, both release their balls at thw same instant. Whose ball hits the ground first? Explain.

(b) A person trying to throw a hall as far as possible will run forward durinf the throw. Explain why this jncreased the distance of the throw.

Answer 1

a) The time of falling of a ball from a height H can be calculated by the formula given below

Here is the initial velocity in vertical direction. In our problem the initial velocity in vertical direction of the ball hold by Jennifer is zero. Similarly the as the ball hold by Daniel moves horizontally so the ball has a initial velocity along the horizontal direction but it has no velocity in the vertical direction. As we have seen time of falling depends only on the initial vertical velocity and the initial vertical velocity of the balls hold by Jennifer and Daniel are same which is zeeo, so both ball will hit the ground at same time. the time when balls will hit the ground is given by

b) if the total time of flight of the ball is t then the horizontal distance traveled by the ball is given by

Where is the velocity of the at the time when it is released from hand. So we see the if the velocity increase the distance D also increase. Now if the person runs with some velocity before throwing the ball, the velocity of the person will increase the velocity of the ball so the ball will go more distance. That is why a person will run forward to throw the ball as far as possible.