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    If I want to find the acceleration of the 3m box,
    and assuming the direction of the net movement is positive,

    I set:

    3mg -k(-2h) - mg = 3a

    since Tension between the strings cancels out,
    there's 3mg acting downwards for 3m box, mg for m box,
    and since the Elastic potential energy is F=-kx where k= 3mg/h (given),
    and the spring is STRETCHED by 2h thus the negative,

    I get 8mg=3a
    a= 8mg/3

    but the answer is 2g

    Am I doing something wrong here?
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    (Original post by liemluji)
    If I want to find the acceleration of the 3m box,
    and assuming the direction of the net movement is positive,

    I set:

    3mg -k(-2h) - mg = 3a

    since Tension between the strings cancels out,
    there's 3mg acting downwards for 3m box, mg for m box,
    and since the Elastic potential energy is F=-kx where k= 3mg/h (given),
    and the spring is STRETCHED by 2h thus the negative,

    I get 8mg=3a
    a= 8mg/3

    but the answer is 2g

    Am I doing something wrong here?
    A logical step would be first to attach the actual question for us to see.
 
 
 
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