An 880 kg cannon at rest fires a 12.4 kg cannonball forward at 540 m/s. what is the recoil velocity of the cannon? (unit m/s)

7.61 m/s backwards

Explanation:

Initial momentum = final momentum

0 = (880 kg) v + (12.4 kg) (540 m/s)

v = -7.61 m/s

The cannon's recoil is 7.61 m/s backwards.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.