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- Thread starter avito009
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Angular momentum is the product of its moment of inertia and its angular velocity. So can we infer that since angular momentum is conserved...

To be more precise: angular momentum is only conserved when there is no net external torque.

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wrobel

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Sorry in advance if that is inappropriate

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jbriggs444

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That is true if we are considering a particular object whose moment of inertia is changing over time (e.g. a skater pulling in her arms).

If we are considering two different objects then the principle does not hold. There is nothing that prevents one skater with a small moment of inertia from spinning slowly while another skater on the other end of the rink has a large moment of inertia and is spinning rapidly.

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CWatters

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and on another thread you wrote..

If a top has angular momentum of 12 units and the earth has angular momentum of 100. Does this mean that Earth is spinning faster than the top since it has more angular momentum? The answer is there at the back of my head but cant articulate it.

Both are wrong.

Angular Momentum is conserved (in systems that don't have an external torque applied). That doesn't mean Angular Momentum is the same for all systems. A car tyre has a much lower moment of inertia than the planet earth yet it's rate of spin (angular velocity) is much higher. Perhaps many revolutions per second compared to one revolution per day.

Moment of inertia is similar to mass...

Linear......... Force = mass * linear acceleration

Rotation...... Torque = Moment of inertia * angular acceleration

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