A) what will an object weigh on the moon's surface if it weighs 500 n on earth's surface? (b) how many earth radii must this same object be from the center of earth if it is to weigh the same as it does on the moon?
alright, i know how to do part a. but i'm having issues on figuring out how to do part b. !

Aparticle initially located at the origin has an acceleration of = 2.00ĵ m/s2 and an initial velocity of i = 8.00î m/s. find (a) the vector position of the particle at any time t (where t is measured in seconds), (b) the velocity of the particle at any time t, (c) the position of the particle at t = 7.00 s, and (d) the speed of the particle at t = 7.00