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10-22-2005
03:00 AM

10-22-2005
03:00 AM

center of mass

A square uniform raft, 18m by 18m, of mass 6800kg, is used as a ferryboat. If three cars, each of mass 1200kg., occupy its NE, SE and SW corners, determine the CM of the loaded ferryboat.

Hi, well thats the question. the book gives me one formula that is appropriate which states:

x CM = mx (A) + mx (b) / m(A)+m(B)

That formula seems to work in one dimensions. So then I was thinking putting the quesiton in 2 dimension x and y. So Id try to find the center of mass along one axis of the boat and then use x and y as components to find the CM. Although I failed trying.

here the answer:

(1.04m, -1.04m) relative to the centre of the raft

Hi, well thats the question. the book gives me one formula that is appropriate which states:

x CM = mx (A) + mx (b) / m(A)+m(B)

That formula seems to work in one dimensions. So then I was thinking putting the quesiton in 2 dimension x and y. So Id try to find the center of mass along one axis of the boat and then use x and y as components to find the CM. Although I failed trying.

here the answer:

(1.04m, -1.04m) relative to the centre of the raft

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3 REPLIES 3

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10-23-2005
03:00 AM

10-23-2005
03:00 AM

center of mass

your approach is correct. You can do the center of mass separately in each dimension. How did you do the calculations? Did you remember to include the boat itself?

� � � � Tom Gutman

� � � � Tom Gutman

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10-23-2005
03:00 AM

10-23-2005
03:00 AM

center of mass

No I did not. How do I take into account the mass of the boat?

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10-23-2005
03:00 AM

10-23-2005
03:00 AM

center of mass

It's just another mass. By symmetry the center of mass of the boat must be at its center. So for the purpose of calculating a center of mass of the whole system it behaves as a point mass at its center.

� � � � Tom Gutman

� � � � Tom Gutman