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 25m/s. Find when and where the two balls meet.
for the ball dropped downwards
s=ut+1/2gt2
s=1/2gt2
s=4.9t2
For the ball thrown upwards
= 100-s=ut-1/2gt2
100-s=25t-4.9t2
therefore
100-s=25t-49.t2
Now add both the equations
100 = 25 t
So t = 4 seconds
S = 4.9 *16 m