Varrying load distance applies a two equal forces on two roller

[GarrettKoep]

Homework Statement

http://img198.imageshack.us/img198/374/20856431.jpg

Homework Equations

Moment = R cross F
Couple moments?

The Attempt at a Solution

I think I have to sum the moments from A, B and L all about C but I am not sure about the relationships between them.

 

[tiny-tim]

Hi GarrettKoep!

I think I have to sum the moments from A, B and L all about C but I am not sure about the relationships between them.

Yes, that's right …

you know the directions of the forces at A B and L, but you have no idea which direction the force is at C, so the only sensible thing is to take moments about C.

And since the angular acceleration is (obviously!) zero, that means that the sum of the torques (moments) must be zero.

What do you get? ​

 

[GarrettKoep]

After summing the moments about C I calculated that b=27

 

[tiny-tim]

Hi GarrettKoep!

After summing the moments about C I calculated that b=27

(How did you get that? Anyway …)

erm … when I said "you have no idea which direction the force is at C", I thought that the "pawl" was rigidly fixed to the rest of the body.

But now that I've looked at the picture more carefully , I realize that the pawl is loose … it can rotate freely at that unnamed point 8" up … let's call that point H.

And since the pawl isn't rotating, that means that the force at C must balance the force at H.

So we know the direction of both the forces at C and at H.

And the rigid body is supported by forces at A B L and H.

Use that information to find the direction and magnitude of the force at H, and then use moments to find b.

Sorry I missed that point earlier. ​

 

[GarrettKoep]

Okay, so if you calculated the sum of the moments about H the equation for b would change from (b-7)*L to (b-9)*L and they others would stay the same ( Fab *20). In conclusion, b would then be equal to 29.

 

[tiny-tim]

If you want anyone to confirm that, you'll have to show your detailed calculations.

 

[nvn]

GarrettKoep: Your current answer is incorrect. Try again.