21. The force is the product of (A) velocity and acceleration
(B) the speed and acceleration
(C) mass and speed
(D) mass and acceleration

grav force prop 1/r squared 2r all squared is 4rsquared 1/4rsquared quartered

im sorry i dont know

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.