From the top of a tower 100 m in height a ball is dropped and at the same time another ball is projected vertically upwards from the ground with a velocity of 25 m/s. Find when and where the two balls will meet? (g=9.8m/s)

Explanation

For the ball dropped from the top
`x=4.9t^(2)" "......(1)`
For the ball thrown upwards
`100-x=25t-4.9t^(2)" "......(2)`
From eq. (1) and (2)
`t=4s,x=78.4m`