If vector b is added to vector a under what conditions does the resultant vector has magnitude a+b?

The vectors must point in the same direction.

jupiter is the largest planet in our solar system, having a mass and radius that are respectively, 318 and 11.2 times that of earth. suppose that an object falls from rest near the surface of each planet and that the acceleration due to gravity remains constant during the fall. each object falls the same distance before striking the ground. determine the ratio of the time of fall on jupiter to that on earth.

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.