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# Physics help, my answer is wrong but only slightly wrong and I can't see where I'm messing up?

A 2.00-m long uniform beam of mass 4.00 kg rests on a fulcrum that is 1.20 m from one end

when a 3.00-kg mass rests on that end and a 8.00-kg mass is placed at another location on the

beam. How far from the end at which the 3.00-kg mass is placed is the location of the 8.00-kg

mass?

I keep getting 1.65m as an answer, but the answer is supposed to be 1.75m, close but not quite. Can someone guide me through this and help me solve it?

### 3 Answers

- ignoramusLv 71 month ago
If you want to know what you are doing wrong, then SHOW what you are doing. We aren't here to guess at your mistakes.

Have you drawn a diagram ? What are the forces and their positions along the beam? Have you understood which forces are clockwise, and which anti-clockwise? That is the first step, and I presume that you have not done this step correctly. Do that properly, and the solution is not difficult.

Basically, if you have any understanding of the situation, you should understand this equation :

Suppose that the 8 kg mass is a distance x from the fulcrum; then

8x = 4(0.2) + 3(1.2)

which gives x = 4.4/8 m = 0.55m

Then distance from the 3 kg mass = 1.2 + 0.55

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- Anonymous1 month ago
1.2(3+4/2*1.2/2) = 0.8*4/2*0.8/2+8*x ..( x = distance from fulcrum)

5.040 = 0.64+8x

x = (5.040-0.64)/8 = 0.55 m

distance d = 0.55+1.2 = 1.75 m

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- Jim MoorLv 71 month ago
A common mistake is not getting the center of mass for each side of the beam times its lever length.

- Yeetus1 month agoReport
Think you can go through solving the problem for me? I'm kinda stumped, we've barely done any examples like this in class

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