# Can an electric motor force angular momentum not to be conserved in an isolated system?

An ice skater is in a spin, she pulls her arms in and she spins faster, she lets her arms extend outward and then she starts to slow down. She will probably weigh on a weigh scale about the same weight during this spin cycle.

Now let us connect an electric motor to her to make her spin faster as she extends her arms outward. Would angular momentum still be conserved? It seems to me that it would not.

Also would she still have the same weight? I think she will weigh less as she is being accelerated by the electric motor.

• Angular momentum is still conserved in the system consisting of the skater, the motor, and whatever the motor is attached to (probably the planet). Why do you think the skater will weigh less? Aug 14, 2012 at 3:15
• Yes Kieth I believe she will weigh a little less if she lets her arms float freely upward as she is spinning. Is there anyone out there who has access to a small portable centrifuge, just weigh it when its not in motion and loaded with someting heavy like mercury for example, then weigh it again when it is spinning under power. Aug 18, 2012 at 1:24
• @ George Jones : I don't think that she will weigh less. She is rotating about an axis perpendicular to the Earth's surface (or along the line of Gravity) so there is no centrefugal force to counter gravity. Aug 20, 2012 at 16:20
• I made some edits, since otherwise the question would have been off topic. Aug 20, 2012 at 17:00