If I was walking would in a circle, my distance and displacement would be the same only if ...   a I walked the full circle.
 b I walked half the circle.  
c I stayed in the same place.  
d I walked the circle twice.

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.