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

[Priyadarshini]

Homework Statement

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

Homework Equations

Moment=Force x perpendicular distance

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[/B]

 

[Qwertywerty]

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

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

 

[Priyadarshini]

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

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?

 

[Qwertywerty]

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

 

[Priyadarshini]

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

It exerts a force in the direction of the rod.

 

[Qwertywerty]

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

 

[Priyadarshini]

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

It should act to that of the rod.

 

[Qwertywerty]

And what have you done in your original solution ?

Hope this helps ,
Qwertywerty .

 

[Priyadarshini]

And what have you done in your original solution ?

Hope this helps ,
Qwertywerty .

Thanks!