Question:
On the earth, a stone is thrown from a height in a direction parallel to the earths surface while another stone is simultaneously dropped from the same height. Which stone would reach the ground first and why ?
Solution:
Both stones will reach the ground simultaneously. Initial velocity of both the stones in the downward direction is zero and the acceleration of both the stones in the downward direction is same and equal to $\mathrm{g}$.
Using $h=u t+\frac{1}{2} a t^{2}$, we get $b=0+\frac{1}{2} a t^{2}$ or $t=\sqrt{\frac{2 h}{g}}$
so both stones take same time to reach the ground.