- #1
gracy
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So my question is when to apply conservation of angular momentum?When there is no external force ,right?But in the case below
A mass m moves in a circle on a smooth horizontal plane with velocity v0 at a radius R0. The mass is attached to a string which passes through a smooth hole in the plane as shown.
The tension in the string is increased gradually and finally m moves in a circle of radius R0/2 . The final value of the kinetic energy is
A) mv20
B) 1/4 mv20
C) 2 mv20
D) 1/2 mv20
My teacher applied conservation of angular momentum.But I don't know why?As tension force is external force the angular momentum should not be conserved.
Note:I am not posting this question in homework sectio because I know it's solution .I don't want method to solve rather I am having a conceptual doubt.
A mass m moves in a circle on a smooth horizontal plane with velocity v0 at a radius R0. The mass is attached to a string which passes through a smooth hole in the plane as shown.
The tension in the string is increased gradually and finally m moves in a circle of radius R0/2 . The final value of the kinetic energy is
A) mv20
B) 1/4 mv20
C) 2 mv20
D) 1/2 mv20
My teacher applied conservation of angular momentum.But I don't know why?As tension force is external force the angular momentum should not be conserved.
Note:I am not posting this question in homework sectio because I know it's solution .I don't want method to solve rather I am having a conceptual doubt.