NOVA physic Torque question

[Futureblackdoc]

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I'm having trouble with these torque problems in which you also have to account for the mass of the meter stick.

Chapter 7 Nova Physics #13. A meter stick of mass .6 kg sits on a fulcrum located at .3m mark at equilibrium. At the 0.0m mark hangs a mass m. What is m ?

One of the official MCAT exams ask a similar question.

 

[anon4895]

I'm having trouble with these torque problems in which you also have to account for the mass of the meter stick.

Chapter 7 Nova Physics #13. A meter stick of mass .6 kg sits on a fulcrum located at .3m mark at equilibrium. At the 0.0m mark hangs a mass m. What is m ?

One of the official MCAT exams ask a similar question.

You have to assume the mass is uniformly distributed, in which case it acts at the center.

 

[Futureblackdoc]

So how would you go about solving it ?

 

[anon4895]

So how would you go about solving it ?

There are two torques here. The torque caused by the weight of the stick and the weight of the hanging mass. They both are trying to spin the meter stick in opposite directions, since the question states they're balanced these torques must be equal.

(.6)(g)(.2) = (.3)(g)(m)

The .2 and .3 are just the distance to the fulcrum. g cancels and m is easy to solve for. Hope this clears it up.

 

[Futureblackdoc]

Where is .2m coming from this is correct, but I'm not understanding it.

 

[anon4895]

Where is .2m coming from this is correct, but I'm not understanding it.

The weight acts in the center bc of what I said in the first post. Since it's a meter stick that means it acts at .5m The fulcrum is at .3m so the distance is .2m

 

[Futureblackdoc]

Ok I see now, thank you !

 

[anon4895]

Ok I see now, thank you !

Glad I could help