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Center of Mass - Man on Boat Homework help

  1. Feb 20, 2015 #1
    1. The problem statement, all variables and given/known data
    A man with mass m1 = 55 kg stands at the left end of a uniform boat with mass m2 = 175 kg and a length L = 2.7 m. Let the origin of our coordinate system be the man’s original location as shown in the drawing. Assume there is no friction or drag between the boat and water.
    1) What is the location of the center of mass of the system? 1.027m
    2) If the man now walks to the right edge of the boat, what is the location of the center of mass of the system? 1.027m
    3) After walking to the right edge of the boat, how far has the man moved from his original location? (What is his new location?) 2.054m
    4)After the man walks to the right edge of the boat, what is the new location the center of the boat?
    5) Now the man walks to the very center of the boat. At what location does the man end up?

    2. Relevant equations
    (m1x1 + m2x2..+mnxn)/(m1+m2....+mn)

    3. The attempt at a solution
    I have calculated the answers for 1, 2, and 3. However, I have not been able to answer questions 4 and 5. Any help would be nice!
  2. jcsd
  3. Feb 20, 2015 #2
    Hey, I think you will want to double check your answers. Without doing any calculations you can see something is off; considering the man moves position between part 1 and 2 yet the location of center of mass stays the same according to what you have written? Is the boat moving for part 3? Please include all information given in the question or possibly a picture of it.
  4. Feb 20, 2015 #3
    This is the image and according to the online homework checker these 3 answers of mine are right. And since there is 0 net force acting on the body it stays same on both edges. Also, for part 3 the boat is moving to the left and I am asked to find where the man moves relative to this specific coordinate system.
  5. Feb 21, 2015 #4
    How fast does the problem state that the boat is moving, which direction is it moving in, is the boat only moving in the latter parts of the problem? In your original post you only state the length/mass of boat and position of the man/his mass relative to the boat, it seems some information is omitted.

    Sometimes when we paraphrase things we forget to include information critical to the problem. If you could give the problem exactly as it is written figuring out the problem will be much smoother.
  6. Feb 21, 2015 #5
    None of this is included in the problem. I copied and pasted the full problem as it was.
  7. Feb 21, 2015 #6
    What is the information given about the movement, only that it is moving left?
  8. Feb 21, 2015 #7
    Yes, that's it. And I've done number 4 now so the only one left to do is number 5!
  9. Oct 16, 2015 #8
    A post on how it was done would be great =)!
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