Two friends, barbara and neil, are out rollerblading. with respect to the ground, barbara is skating due south at a speed of 6.3 m/s. neil is in front of her. with respect to the ground, neil is skating due west at a speed of 2.4 m/s. find neil's velocity ((a) magnitude and (b) direction relative to due west, as seen by barbara.

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.