# QUESTION - NO FORCE IS ACTING ON A NONRIGID BODY , STILL ITS ANGULAR AND LINEAR MOMENTUM REMAINS CONSTANT HOW ?

SAGAR SINGH - IIT DELHI
879 Points
11 years ago

Dear student,

he angular momentum of a system of particles (e.g. a rigid body) is the sum of angular momenta of the individual particles. For a rigid body rotating around an axis of symmetry (e.g. the fins of a ceiling fan), the angular momentum can be expressed as the product of the body's moment of inertia I (a measure of an object's resistance to changes in its rotation rate) and its  ω:

$\mathbf{L} = I \boldsymbol{\omega} \, .$

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Sagar Singh

B.Tech, IIT Delhi

509 Points
11 years ago

F = mdv/dt

if F = 0 then ,

dP/dt = 0

this is possible if, P = k(constant ) coz differentiation of constant is always 0....

P = constant ...          (momentam remains constant)

now , T(torque) = dL/dt                              (L is angular momentam)

if T is 0 then

dL/dt = 0

L = k(constant)                      (angular momentam remains conserved)

if force is 0 then we can say that linear momentam is 0 but we cannot say anything about angular momentam ...

eg=> a disk is moving  on a horizontal surface  ,

case1)

two equal forces in opposite direction acts towards center then no net force acts on center of mass so its linear  as well as angular momentam will remain conserved ...

case2)

if forces are not acting towards center but are in opposite direction then also net force on center of mass is 0 but these forces are producing torque so angular momentam will change...

approve if u like my ans