A ball is thrown upward at the speed of 10m/s from the top of the tower reaches the ground with the speed of 20m/s. The height of the tower is
A ball thrown vertically upwards with a speed of 20m/s from the top of a tower reaches a certain height and then falls back to the earth in 6 s. Find the height of the tower. [Take acceleration due to gravity, g=10 m/s2]