Problem-solving: Moon orbit around the earth

Do you want to be really good at problem-solving? The key is to get plenty of practice.

Here is one of the problems from i-want-to-study-engineering.org, a practice website designed for students who plan to apply for Engineering at top universities:

Assuming that:

  • the average distance between the earth and the moon is 3.8 x 108 m,
  • on average, it takes the moon 29 days to go round the earth,
  • the approximate value of the universal gravitational constant
    G= 6.7 x 10-11m3kg-1s-2.

estimate the mass of the earth.

Is the answer:

  • approximately 5 x 1023kg?
  • approximately 6 x 1024kg?
  • approximately 7 x 1025kg?
  • approximately 42kg?
  • None of the above?

For hints, topic information and answers, see the problem page itself, or for more problems (there are more than 200 available), see the problem index.

Further information:

Date posted: 

Tuesday 26 May 2015

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