IIT JEE , AIEEE Forum - Physics , Mechanics

utsavsharma17

I want to know about conservation of Angular Momentum.

coolvignesh

like there is conservation of linear momentum...
there is cons. of ang. momentum.....
in linear momentum.. Momentum is conserved if there is ext. force....
in same way.. ang. momentum is conserved if no external torque acts on the system..........or u can say that no force acting on the particle produces turning effect

annihilator

If the net torque acting on a body is zero,then the ang momentum of the body about the axis of rotation is constant.Or in other words,

=0

dL/dt=0 or L=constant.
where L denotes the ang momentum.

Examples:
If ice melts on poles or earth suddenly shrinks in size or expands or a ballet dancer stretches or folds arms,no torque is applied and ang. momentum is conserved.But rember tht ang velocities will change w/o ang accel bcoz M.I chnges due to re-distribution of masses.

L=I₁

₁=I₂

₂

waterdemon

"The Law of conservation of angular momentum states that

if no external torque acts on a body rotating about a fixed

point, the angular momentum of the body remains constant"

when external forces act on the particles,they exert torque

on them. Now the angular momentum of the particles change

with time. The rate of change of angular momentum is given

by:

dL =

d (r x p)

dt dt

On solving we will get

dL = (Torque)ext

dt

Now if in a system no external torque acts then we have :

dL = 0

dt

means here L = constant

Hence,This shows that in a rotatory motion, if no external

torque acts on the system of particles, the angular momen

tum remians constant. This is the law of " conservation of

momentum"

Hope you find it useful.

Cheers ! ! ! ! @ @ ! ! ! !

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