Does two dimensional motion imply conservation of angular momentum?

  • #1
Hello!

I have a system composed by a particle attached to four springs that lie on the xy plane. The motion of the particle occurs on the xy plane. I wanted to know if the angular momentum is conserved. Thanks for your help :)
 

Answers and Replies

  • #2
K^2
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Momentum is conserved if there is no external torque. If you have multiple springs going to a point, you probably have some torque on that point.
 
  • #3
HallsofIvy
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Perhaps you are thinking "the angular momentum vector is perpendicular to the plane of motion. Since this is two dimensional, there cannot be such a vector." That is mistaken. The fact that motion is "two dimensional" means that the motion occurs in two dimensions. It does not mean there is NO third dimension.
 
  • #4
I know the angular momentum is orthogonal to the plane of motion, but I would like to know if it is constant.
 
  • #5
K^2
Science Advisor
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Not in general, no. If the springs were attached to other objects that are free to move, it would be, because that would be a closed system. But if springs are attached to fixed points, it's the same as supplying external torque, so angular momentum will not be conserved.
 

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