how to find the mass of an object end A?

Question

rane · Answer

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rane · Answer

The line is the mobile hanging from the ceiling which comprises 2 objects suspended from wires attached to a light horizontal rod 60cm long. At end B hangs a 200g objectt whilst a heavier objectt hangs at A. 
the rod has a mass of 100g and the mobile balances at a point 15cm from point A

rane · Answer

@shamim and...?

rane · Answer

how would I find that ?
can u give me a formula ?

rane · Answer

don't we use the mass of the rod and the the mass of object B as well as the distance between  the mobile and point A ????

aravindg · Answer

Without any doubt you can straight away go for rotational equilibrium here. The torques balance each other and results in the equilibrium condition.  Form the equations and you can solve for the weight easily :)

rane · Answer

but there are 3 weight forces acting on it

aravindg · Answer

So what?

rane · Answer

wht would be the eauqation then ?

aravindg · Answer

Equate the torques about any point?

rane · Answer

at point A

rane · Answer

@AravindG

aravindg · Answer

|dw:1396326057539:dw| That point is better.

aravindg · Answer

Or wait...try both :P

rane · Answer

??

aravindg · Answer

15 is length of string right?

rane · Answer

no, the distance between the string and the point A

aravindg · Answer

Sorry I am not getting the diag correctly :/

rane · Answer

ok w8, i'll pu the arrows

rane · Answer

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