A Challenge!

If the mass of Mars is 0.107E and its radius is 0.53RE, estimate the gravitational field g at the surface of Mars.
設地球質量為M0，半徑為R0，火星的為M，半徑為R

則對地球表面物體m0

G(M0m0)/R0^2=m0g0


對火星表面物體m

G(Mm)/R^2=mg

g/go=(M/M0)(R0/R)^2=(0.107)(1/0.53^2)=0.3809

the gravitational field g at the surface of Mars

=0.3809*g0

=0.3809*9.8

=3.73ms^-2