SAT物理题

题目

SAT物理题
The Earth has radius of 6400 kilometers. A satellite orbits the Earth at a distance of 12800kilometers from the center of the Earth. If the weight of the satellite on Earth is 100 kilonewtons, the gravitational force on the satellite in orbit is
A 11 kilonewtons B 25kilonewtons C 50kilonewtons D 100kilonewtons E 200kilonewtons

答案

B 25kilonewtons.
万有引力公式:F=G*(M地m卫)/r2
G=6.67*10^-11
M地=5.976*10^24 kg
M卫=100000N=10000kg
r=12800km=1.28*10^7 m
代进去化简算出来约等于24.32.
BTW,本来我也想考SAT2,不过后来没时间放弃了.