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