Answer:
6.17 m
Explanation:
We are given that
Initial speed of rubber ball, u=12 m/s
Total height, h=7 m
Initial speed of second ball, u'=0
We have to find the height at which the two balls collide.
Let first rubber ball and second ball strikes after t time.
For first ball
Distance traveled by first ball in time t

Substitute the value

...(1)
Distance traveled by second ball in time t

.....(2)
Using equation (2) in equation (1) we get



sec
Now, using the value of t

S=6.17 m
Hence, at height 6.17 m the two balls collide .