Multiple Choice. On August $6,2012,$ the Curiosity rover landed on the surface of Mars. What is the force of gravity acting on the Mars rover? Curiosity has a mass of $900$ kg $,$ Mars has a mass of $6\mathrm{.}42{10}^{23}kg$ and a mean radius of $3\mathrm{.}39{10}^{6}m.$

a$)4200$ N

b$)3350$ N

c$)5620$ N

d$)926$ N

Calculate the orbital speed of a satellite that is $100$ km above the surface of the earth. The mass of the earth is $5\mathrm{.}97{10}^{24}kg$ and its mean radius is $6\mathrm{.}37{10}^{6}m.$

a$)2\mathrm{.}94k\frac{m}{s}$

b$)3\mathrm{.}70k\frac{m}{s}$

c$)7\mathrm{.}85k\frac{m}{s}$

d$)8\mathrm{.}64k\frac{m}{s}$