Chapter 5, Problem 9A

At the instant a ball is thrown horizontally over a level range, a ball held at the side of the first is released and drops to the ground. If air resistance is neglected, which ball strikes the ground first?

To determine

The ball that strikes the ground first.

Answer to Problem 9A

Both balls strike the ground at the same time.

Explanation of Solution

Introduction:

As per the kinematics equation, time of travel of an object depends on initial velocity, displacement and acceleration of the object.

Both the balls have same initial zero velocity in the vertical direction. Since both the balls starts at same vertical height, the vertical displacement of each ball is also same. Also, since both the balls are in projectile motion, both experience same acceleration due to gravity in vertical direction. Since both the balls have same initial velocity, displacement and acceleration, the time to hit the ground is same for both the balls.

Conclusion:

Hence, both balls strike the ground at the same time.