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Homework Help: Mass and weight problem

  1. Feb 7, 2016 #1
    1. The problem statement, all variables and given/known data
    The largest piece of equipment that an astronaut on Earth can lift has a weight of 392 N. On the Moon, the acceleration due to gravity is only 1.62 m/s^2.
    a) What is the mass and weight of the same piece of equipment on the Moon?
    b) What is the mass and weight of the largest rock the astronaut can lift on the Moon?

    2. Relevant equations

    3. The attempt at a solution
    For a), I found that the mass had to be 40kg on the Moon because mass does not change whether you're on Earth or on the Moon. For the weight, I just multiplied 40kg * 1.62 m/s^2 and found that the weight is 65 N.
    For b), I am confused about what it is asking because isn't it the same answer as a)? If the largest equipment that the astronaut can handle is 40 kg, then a rock must be a max of 40 kg and wouldn't the weight also be 65 N? Quick help would be much appreciated.
  2. jcsd
  3. Feb 7, 2016 #2


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    There's a subtle difference between the answers to a) and b).

    On earth, as astronaut's muscles provide the force necessary to lift a piece of machinery with a certain mass against the acceleration due to earth's gravity.

    How much mass under the moon's acceleration due to gravity is equivalent to the maximum force which can be exerted by the astronaut?
  4. Feb 7, 2016 #3
    I still don't understand... wouldn't that give me the same answer or do I need a different equation for part b) to find the answer?
  5. Feb 7, 2016 #4
    I kept reading your reply and this is my understanding:
    So the maximum force which can be exerted by the astronaut is 392 N, correct? So, I just have to plug in 392 N into W=mg in terms of the moon's acceleration to find the mass?
  6. Feb 7, 2016 #5


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