Answers

2016-02-06T01:43:49+05:30
Since after 0.4cm exentention spring hangs in equlibirium 
threfore net upward force = net downward force
Kx=mg
K=mg/x
K* 0.04 = 0.04 * 10    (4cm =0.04m and 40 g =0.04 Kg net force downward =mg)
K=10 (if gravity taken as 10 other wise 9.8)

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