A ball is thrown straight upward from ground with a speed of 20 ~m / s . The ball was caught on its way down at a point 5 ~m above the ground. The time taken by the ball during entire trip is (assume, g=10 ~m / s ^2 )

Step-by-step solution

The given situation of entire motion of ball is shown in the following figure. Initial speed of ball, u=20 ~m / s Total time taken by the ball to reach at highest point P is t₁ , then from equation of vertical motion v=u-g t 0=20-10 t₁ t₁=2 ~s Maximum height attained by the ball is h , then from equation h=u t- 1 2 g t^2=20 2- 1 2 10 2^2=40-20=20 ~m If t₂ be the time taken by the ball to reach at B from point P , then aligned h-5 & =0 t₂+ 1 2 g t₂^2 20-5=0+ 1 2 10 t₂^2 15 & =5 t₂^2 t₂= 3 ~s aligned Time taken by th