How much torque must the pin exert to keep the rod from rotating?

[nweis84]

Homework Statement

How much torque must the pin exert to keep the rod from rotating?
(L=1.011m , M=3kg , m = .301kg)

So I am guessing the point of rotation is the pin??
But then how does the pin exert any torque if it is at the point of rotation?
I'm not quite sure


there is a sketch I've attached

Homework Equations

Ive used the equation $$\Sigma$$$$\tau$$net=0=$$\tau$$pin-$$\tau$$M-$$\tau$$m

The Attempt at a Solution

i have tried it so many ways and keep getting it wrong

$$\tau$$pin = 3kg*(1.011m/2) + .301kg*1.011m
what am i doing wrong?
Please help thankyou

 

[JaWiB]

For this type of problem, you probably don't need to worry about how the pin exerts a torque (though you can imagine in reality it would take a fair amount of force since there is only a small lever arm)

It looks like you've neglected to calculate the force of each of the masses and are using the mass instead (kg*m is not the units of force)

 

[nweis84]

yeah thank you i did forget to multiply by the acceleration constant g