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# M2 - Centre of Mass Tweet

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1. M2 - Centre of Mass

I'm stuck on Q6 i)

I THOUGHT I was good at this but I think I'm just making a simple mistake and can't see where; working:

Midpoint of CD (9,9); center of mass of triangle is two thirds the way up the line E to midpoint of CD.

(0,3) to (9,9)... centre of mass = (6,7)

area = 1/2 x 12 x 9 = 54

Centre of mass of rectangle (1.5,4.5) with area 27.

27 * 1.5 + 54 * 6 = 81x, x = 4.5 (wrong)
27 * 4.5 + 54 * 7 = 81y, y = 37/6 (wrong)

?
2. Re: M2 - Centre of Mass
Heh, should be (3,0) not (0,3), doh!
3. Re: M2 - Centre of Mass
(Original post by Kasc)
(0,3) to (9,9)... centre of mass = (6,7)

area = 1/2 x 12 x 9 = 54

Centre of mass of rectangle (1.5,4.5) with area 27.

27 * 1.5 + 54 * 6 = 81x, x = 4.5 (wrong)
27 * 4.5 + 54 * 7 = 81y, y = 37/6 (wrong)

?
The centre of mass of your triangle is at (7,6), not (6,7)