Step-by-step explanation:
In order to calculate the average force exerted we need to calculate the mass of water droplet first of all as follows.
Volume =

=

As we know that density of water is 1000
. The mass is given as follows.
m =

=

=

As the given water droplet falls from a height of 9 m. Therefore, its velocity when it hits the ground is as follows.
v =

=
m/sec
= 13.28 m/sec
Now, we will calculate the rate of droplet fall as follows.
R =

= 0.25 drops/sec
Therefore, force will be calculated as follows.
F =
(
)
=

= 8.632 N
Thus, we can conclude that 8.632 N is the average force exerted on the limestone floor by the droplets of water during a 7 min period.