Objects 1 and 2 attract each other with a electrostatic force

of 18.0 units. If the distance separating Objects 1 and 2 is

changed to four times the original value (i. e., quadrupled),

then the new electrostatic force will be units.

1.125

Electrostatic force changes like the inverse square of the distance (just like gravity).

If you double the distance, you change the force to 1/4 of what it used to be.

After the move, Objects 1 and 2 attract each other with a force of (18/16) = 1.125 units.