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Homework Statement
Overhead view of a spring lying on a frictionless surface and attached to a pivot at its right end.The spring has a relaxed length of ##l_0=1.00m## and a negligible mass.A small 0.100 kg disk is attached to the free end at left.That disk is then gvena velocity ##\vec {v_0}## of magnitude ##11\frac {m} {s}## perpendicular to the springs lenght.The disk and spring then move around the pivot.
(a)When the streching of the spring reaches its maximum value of ##0.100l_0##, what is the speed of disk,
(b)What is the spring constant ?
Homework Equations
[/B]Energy conservation.
The Attempt at a Solution
[/B]From Newtonian equations we know that ##fx=\frac {mv^2} {r}## so from that we can obtain ##1.1k=v^2##
Then I wrote energy conservation
İnitally it has a speed ##11\frac {m} {s}## and later time it will have some velocity v' and there's also spring potantial energy
Here I stucked,Do I have to add rotational energy of spring-disk system ? I think I should but I got wrong result.
The equation will be ##\frac 1 2m(v_0)^2=\frac 1 2m(v')^2+\frac 1 2kx^2##
here
##x=0.1m##
or ##\frac 1 2m(v_0)^2=\frac 1 2mI(w)^2+\frac 1 2kx^2## but its same as upper equation.
Any help ?