Laws of Motion-5

B ) 0.2 m

on 1 kg block there is a net force of 10 N upward
i.e. , on spring ,
upward force =10 N and
downward force = 30 N
.
. . the net force on spring = 30-10 = 20 N

Hence ,
extension = F/K
= 20 / 100
= 0.2 m

d ans is 0.2 m .....
but plz check my method of solvin...
took the 1 kg and 3kg block to be a system of 4kd mass, found the accn for that system which came to be g/3
then , tension in the spring is calculated frm 3g-T=3a where a=g/3.. T=2g=20N
thus extension is 0.2m
is d process correct....??

0.2m

See we r getting 3 equations......
T=2a+2g
3a+kx=3g
T+a=g+kx
3 equations and 3 variables(T,a and x)....solve it....u will get d answer to be 0.2m

yes sir..thnk u!!