Objects 1 and 2 attract each other with a electrostatic force of 18.0 units. if the charge of object 1 is doubled and the distance separating objects 1 and 2 is tripled, then the new electrostatic force will be units.

The electrostatic force between two charged objects is given by

where
k is the Coulomb's constant
q1 and q2 are the two charges
r is the separation between the two charges

In this problem, the charge of object 1 is doubled:

while the distance between the two objects is tripled:

Therefore, the new electrostatic force will be


And since the original force was F=18.0 units, the new force is