According to the universal law of gravitation, if the separation between two planets is increased by a factor of 8, how many times weaker will their mutual pull of gravity be?

weakens by 64 times  

Explanation:

According to universal law of gravitation the force between two bodies is inversely proportional to square of their distance between them that F is inversely proportional to

So if we increase the the distance between two planets by 8 times then the the mutual attraction between will be decrease by times  

what type of charge does it have? negative

the working equation for the angular size is the product of the physical size and 360 degrees divided by the product of two pi and distance from earth. the minimum size would be 0.559 degrees while the maximum size would be 0.49 degrees.