# Homework Help: Torque problem

1. May 12, 2012

### reder

Hello I've attached the problem. Any help would be greatly appreciated.

I understand that by giving us the clue of rotational equilibrium, it means net T has to be 0. The force at 10N will cause clockwise torque (T= rF, so T = .04m * 10N). The thing that confuses me is the force at point B, will it cause counterwise torque or no torque? Also I know the force that we are finding at point D will give us counterclockwise torque, but is the moment arm or lever arm going to be .04m too?

Thank You.

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2. May 12, 2012

### Infinitum

Re: Torque

Hi reder! Welcome to PF!

You're right there!

Think about a situation of such a hinged block, and you applying adequate force to it at the lower end(B). Would it rotate? If yes, which way?

By definition, torque about a point is the force multiplied by the perpendicular distance between the line of action of force and the point. What does that tell you about the lever arm length?

3. May 12, 2012

### reder

Re: Torque

Think about a situation of such a hinged block, and you applying adequate force to it at the lower end(B). Would it rotate? If yes, which way?
My guess would be, it would rotate counterclockwise.

By definition, torque about a point is the force multiplied by the perpendicular distance between the line of action of force and the point. What does that tell you about the lever arm length? [/QUOTE]
So I can just extend the line of action of force at point D and this in turn would make it the lever arm .04m.

So if I am taking clockwise as negative torque and counterclockwise as positive torque..... - -.04(10N) + (5N) (.02) + (F) (.04)= 0
.4 = .1+ .04F
F = 7.5N.......(Is my reasoning correct)......
Also thx for a quick reply......

4. May 12, 2012

### Infinitum

Re: Torque

Right-o!

Absolutely.

5. May 12, 2012

### reder

Re: Torque

Thx infinitum for the help....

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