A Uniform Rod Is Attached To A Point With A String---Moments

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1. Aug 20, 2015

1. The problem statement, all variables and given/known data

Use the principle of moments and take moments about A to show that the weight of the object O is 19 N.

2. Relevant equations

Moment=Force x perpendicular distance
3. The attempt at a solution
Vertical component of tension= TsinA
= 30sin50
=23N
(8.5 x 0.6) = (9.8M-23) x 1.2
5.1/1.2 = 9.8M-23
9.8M=27.25
As w=mg, the W= 27.25N
But the answer is supposed to be 19N

2. Aug 20, 2015

Qwertywerty

You have made an error in balancing moments . Which moment acts in which direction ?

3. Aug 20, 2015

One acts clockwise from point B, I am not so sure about the other. Does it act anticlockwise from point A or does it act at the centre?

4. Aug 20, 2015

Qwertywerty

In which direction does gravity exert a force on M ? Is it in the direction of tension or the rod ?

5. Aug 20, 2015

It exerts a force in the direction of the rod.

6. Aug 20, 2015

Qwertywerty

So should it's moment add to that of the rod's , or should that of the tension's ?

7. Aug 20, 2015

It should act to that of the rod.

8. Aug 20, 2015

Qwertywerty

And what have you done in your original solution ?

Hope this helps ,
Qwertywerty .

9. Aug 20, 2015