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Center of Mass - Man on Boat Homework help

  • Thread starter Lydia5
  • Start date
  • #1
4
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Homework Statement


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?

Homework Equations


(m1x1 + m2x2..+mnxn)/(m1+m2....+mn)

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!
 

Answers and Replies

  • #2
13
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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.
 
  • #3
4
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manonboat.png

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.
 
  • #4
13
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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.
 
  • #5
4
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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.
None of this is included in the problem. I copied and pasted the full problem as it was.
 
  • #6
13
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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.
What is the information given about the movement, only that it is moving left?
 
  • #7
4
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Yes, that's it. And I've done number 4 now so the only one left to do is number 5!
 
  • #8
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A post on how it was done would be great =)!
 

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