I'm completely stumped on 2 questions I have, I'm not even sure which formula's to use, I've tried many.... any help??(adsbygoogle = window.adsbygoogle || []).push({});

1) Lunar gravity at the Moon's surface is only 1/6 as strong as what we experience on Earth. Since the diameter of the Moon is about 1/4 that of the Earth, the lunar mass is about :

a) 3 x 10^-3 times the Earth's mass

b) 1 x 10^-2 times the Earth's mass

c) 3/8 the Earth's mass

d) 1/3 of the Earth's mass

e) 3 times the Earth's mass

2) At what point between the Earth, mass M_E and the Moon, mass 0.0123 M_E will their gravitational fields cancel each other (i.e. at what point willa small mass experience zero net force?)

a) at the centre of the Earth

b) At the centre of mass of this sysytem

c) at a distance 50% between the two

d) At a distance 74% of the way from the Earth to the Moon

e) none of these

Any help to set me on track would be really appreciated! Thanks

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# Homework Help: Problems - Gravity & Mass of Earth & Moon

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