The gravitational force between two masses is given by:

where
G is the gravitational constant
m1 and m2 are the two masses
r is the separation between the two masses
We see that the force is proportional to the inverse of the square of the distance:

therefore, if the distance is tripled:
r'=3r
The force decreases by a factor 1/9:

Since the original force was 36 N, the new force will be
Answer:
7 m/s
Explanation:
To solve this problem you must use the conservation of energy.

That math speak for, initial kinetic energy plus initial potential energy equals final kinetic energy plus final potential energy.
The initial PE (potential energy) is 0 because it hasn't been raised in the air yet. The final KE (kinetic energy) is 0 because it isn't moving. This gives the following:


K1=U2

Solve for v

Input known values and you get 7 m/s.