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Re: [Phys-L] A suspended metal rod

Nothing wrong with the question. The torque equation will tell you where the center of mass of the rod is. However, it is
probably easy to make an unwarranted assumption about the position of the CM and get inconsistent answers.

You're right! I didn't see it at first but the center of mass of the rod is located 0.75 m from the end where Cable 1 is attached.

So, the students who calculated the tensions using only the first condition (sum of forces equals zero) got the right answers, about 36 N and 62 N, respectively, for the tensions in Cables 1 and 2.

If the problem had stated that the rod was uniform, then it'd be ill-posed.

Herman Trivilino
College of the Mainland
Texas City, Texas

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