# Varrying load distance applies a two equal forces on two roller

1. Oct 10, 2009

### GarrettKoep

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

http://img198.imageshack.us/img198/374/20856431.jpg [Broken]

2. Relevant equations
Moment = R cross F
Couple moments?

3. 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.

Last edited by a moderator: May 4, 2017
2. Oct 11, 2009

### tiny-tim

Hi GarrettKoep!
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?

3. Oct 11, 2009

### GarrettKoep

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

4. Oct 11, 2009

### tiny-tim

Hi GarrettKoep!
(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 realise 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.

5. Oct 11, 2009

### 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.

6. Oct 11, 2009

### tiny-tim

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

7. Oct 11, 2009

### nvn

GarrettKoep: Your current answer is incorrect. Try again.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook