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Thread: pulley system

  1. #1
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    pulley system

    I am confused on part (ii) usually if i was finding the normal reaction of something i take all net forces going down on a object and let that equal R, the normal reaction.

    here they use F=ma. I do not see why they even use this. is another correct way to do the question is to add 1N and 2N and let that equal to R. or is that incorrect and just coincidence you get the same answer?

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  2. #2
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    Re: pulley system

    Your assumption is true for a system which is resting and in an equilibrium. In the problem, it is mentioned that the weights are moving with certain acceleration. Once the system is in motion, you need to use the principles of motion (Newton's second principle here).
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  3. #3
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    Re: pulley system

    silly me. I forgot to post part (ii) of the question.

    pulley system-thurs.png

    when using R-2=g/2 (2/g) why do they not take into consideration the weight and motion of the scale pan?
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