This one:
http://targetiit.com/iit_jee_forum/posts/an_extension_309.html
a system consists of two cubes of masses m1 & m2 respectively connected by a spring of force constant k . find the force (F) that should be applied to the upper cube for which the lower one justs lift after the force removed
Sorry din read the question correctly :)
this question is solved on the forum already..... (it was by given by priyam.. )
let me find the question..
priyam this is the same question as burning of thread... (only presented slighty differently)
This one:
http://targetiit.com/iit_jee_forum/posts/an_extension_309.html
here if F is applied in above direction then for lower block m_{2}g=kx
for upper block F=m_{1}g+kx
if the force is applied in downward direction then...... ;)
yup this one only..
the only difference is that masses will change :)
aman the solution is a bit lengthy...
just give me a couple of hours i will try to post the full solution...
sorry dudee a couple of hours have changed to a couple of days...
when u apply a force in the downward directin, the fbd of the upper mass will have its mg, F in the downward direction and kx in the upward
hence
F+mg=kx
to lift both masses, force must be equal to total weight.
F=(m1+m2)g