TBR Limiting Cases

[deleted92121]

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Not sure I am getting the concept totally and it seems like a good idea so I prefer to utilize any tips/tricks/shortcuts at my disposal.

From what I have gathered you choose two extreme opposites because you know what that will cause (m1 = m2 in atwood machine gives a = 0 due to newton's laws). So do you know you have the right answer (a, b, c, or d) when you find the equation that makes this true?

 

[Jepstein30]

Probably better if you provide an example but its a fairly useful technique. It's hard to really remember to use it/find a problem that is suited for it but if you're given four answer choices with new equations, it's certainly something that you can pull from your toolbox to get a question right.

It may not completely eliminate all the other answer choices but it should do some of the work for you. If I understand which problem you are referencing, then yes.. if only one of the answer choices yields what you know should happen, then it has to be correct.