How Does a Wax Blob Affect the Angular Velocity of a Rotating Rod?

AI Thread Summary
The discussion centers on a physics problem involving a rod and a falling wax blob, focusing on how the blob's collision affects the rod's angular velocity. Participants clarify that energy conservation cannot be applied due to the inelastic nature of the collision, where the blob sticks to the rod. Instead, conservation of angular momentum is suggested as the appropriate approach to determine the new angular velocity after the collision. The conversation emphasizes the need to justify the assumptions made when applying angular momentum conservation. Ultimately, the key takeaway is that the collision alters the system's dynamics, necessitating a different conservation principle for analysis.
nil1996
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Homework Statement


A rod of length L and mass M is pivoted at the center C such that it can freely rotate in vertical plane.Initially the rod is at horizontal position.A blob of wax of mass M falls vertically with speed V and sticks to the rod midway between center and one end.If the rod rotates with angular speed ω what will be the angular velocity in terms of V and L?


Homework Equations



none

The Attempt at a Solution



Can i use energy conservation here.The kinetic energy carried by the wax blob will be transferred into rotational energy.Is this approach right?
 
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nil1996 said:

Homework Statement


A rod of length L and mass M is pivoted at the center C such that it can freely rotate in vertical plane.Initially the rod is at horizontal position.A blob of wax of mass M falls vertically with speed V and sticks to the rod midway between center and one end.If the rod rotates with angular speed ω what will be the angular velocity in terms of V and L?


Homework Equations



none

The Attempt at a Solution



Can i use energy conservation here.The kinetic energy carried by the wax blob will be transferred into rotational energy.Is this approach right?

No, the blob sticks to the rod, it is inelastic collision.

ehild
 
So how do we calculate how much energy was useful from that collision?
 
i think using conservation of angular momentum will get me the answer.right?
 
Yes, but you should justify this assumption.
 

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