Mass Impact on Hinged Rod: Single Plane Explained

AI Thread Summary
A mass impacting the end of a hinged rod causes the rod to rotate, with the motion confined to a single plane. This plane is defined as being normal to the hinge's axis, which is crucial for understanding the conservation of angular momentum. The discussion highlights confusion regarding the concept of a single plane, questioning whether it relates to x,y coordinates or the limitations of linear momentum. The analogy of a door's keyhole illustrates that the motion remains within a defined plane, despite the circular trajectory of the mass and rod. Understanding this single plane is essential for analyzing the dynamics of hinged objects.
captainjack2000
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1. A mass is hitting the end of a hinged rod. After impact they begin to rotate.
The motion is then confined to a single plane. why? what plane?

3. I am a bit confused by what they mean by a single plane. Are they saying that there are only x,y coordinates? Is this just a condition for the conservation of angular momentum or a reason why linear momentum cannot apply?
 
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The motion of any point on a hinged object is always confined to a single plane in the lab-frame. This is the plane that is normal to the axis provided by the hinge.

Consider, for example, the motion of the keyhole on a door, as the door rotates.
 
I'm sorry but I still don't understand why it has to be considered in the single plane?
 
The motion of the mass and the rod is a circle. Circle lies in a place, perpendicular to the angular momentum vector of the objects moving round the hinge... I think
 

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