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Internal and external torques.

  1. Apr 11, 2014 #1
    How do I tell if a torque on a system is internal or external before conserving angular momentum? I know that if a force has its reactionary force in the system, then it is an internal force and we can conserve the linear momentum of the system. But I don't know how to recognize a reactionary torque. For example, if two rough rotating bodies (say cylinders) are brought into contact with each other, the torque experienced by them due to friction is different and hence the angular momentum cannot be conserved in this two-body system even though the forces are all internal.
  2. jcsd
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