Help ASAP!!
Which of the following is closest to the weight in Newtons of a 20 kg object on the Earth’s surface? Given g = 10 m/s²

A.) 200N
B.) 350N
C.) 400N
D.) 20N

Ihave no idea how to solve these. plus there's another question that is 2) a 10 kilogram meteorite is collected in space and brought back to earth. it is composed of 1.25 kg of uranium-238 and 8.75 kg of lead-206. how many u-238 half lives have passed? what is the approximate age of the meteorite?