Question

A ball is projected with velocity 10m/s at an angle of 30 degrees with the horizontal surface . The time taken by the ball to reach the ground is ... g=10

Answer 1

The ball's vertical position in the air is given by

$y=10\cos30^\circ\,t-\dfracg2t^2$

and it will reach the ground at $t$ for which $y=0$:

$0=5\sqrt3\,t-5t^2=5t(\sqrt 3-t)\implies t=\sqrt3\approx1.73$