If two objects are electrically attracted to each other
both objects must be negatively charged.
both objects must be positively charged.
one object must be negatively charged and the other object must be positively charged.
the objects could be electrically neutral.
none of the above statements are absolutely true

Identify the correct relation showing that the radius r of the orbit of a moon of a given planet can be determined from the radius r of the planet, the acceleration of gravity at the surface of the planet, and the time τ required by the moon to complete one full revolution about the planet. determine the acceleration of gravity at the surface of the planet jupiter knowing that r = 71 492 km and that t= 3.551 days and r= 670.9 × 10^3 km for its moon europa.