Why is there are precession frequency here?

AI Thread Summary
The discussion revolves around the concept of precession frequency in relation to a spinning disk and a rod piercing through its center. The user questions how precession occurs if the weight does not create torque, suggesting that a horizontal change in angular momentum is not possible. They also raise scenarios where the axis of rotation is slightly tilted or the surface is uneven, which could influence the precession. These factors may introduce additional torque, leading to precession despite the initial conditions. Understanding these dynamics is crucial for analyzing the system's behavior.
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Homework Statement
A child's toy top consists of a uniform thin disk of radius 5.0 cm and mass
0.15 kg with a thin spike passing through its center. The lower part of the
spike protrudes 6.0 cm from the disk. If you stand this top on a table and start
it spinning at 200 rev/s, what will be its precession frequency?
Relevant Equations
.
so I need to use the eq.: omega_pr = ##mgr / L_s## with r = 6cm.
But from how I imagine/see it, the rod pierces the disk through the middle so how does this create precession if the weight will not cause a torque then and thus a hortizontal change in angular momentum?

Thanks in advance!
 
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What if the axis of rotation is slightly tipped when the toy is started spinning? What if the surface on which it is spinning is not exactly flat? You get the point.
 
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