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Question-69746




Question Number 69746 by jagannath19 last updated on 27/Sep/19
Commented by jagannath19 last updated on 27/Sep/19
answer with explanation
$${answer}\:{with}\:{explanation} \\ $$
Answered by mr W last updated on 27/Sep/19
before cut:  force in string between A and B is  F_1 =mg  force in spring over A is  F_2 =2mg  just after the string between A and B  is cut, only F_2  remains, F_1 =0, we have  F_2 −mg=ma_A   ⇒a_A =((2mg−mg)/m)=g (upwards)
$${before}\:{cut}: \\ $$$${force}\:{in}\:{string}\:{between}\:{A}\:{and}\:{B}\:{is} \\ $$$${F}_{\mathrm{1}} ={mg} \\ $$$${force}\:{in}\:{spring}\:{over}\:{A}\:{is} \\ $$$${F}_{\mathrm{2}} =\mathrm{2}{mg} \\ $$$${just}\:{after}\:{the}\:{string}\:{between}\:{A}\:{and}\:{B} \\ $$$${is}\:{cut},\:{only}\:{F}_{\mathrm{2}} \:{remains},\:{F}_{\mathrm{1}} =\mathrm{0},\:{we}\:{have} \\ $$$${F}_{\mathrm{2}} −{mg}={ma}_{{A}} \\ $$$$\Rightarrow{a}_{{A}} =\frac{\mathrm{2}{mg}−{mg}}{{m}}={g}\:\left({upwards}\right) \\ $$

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