Tuesday, November 6, 2018

rotational kinematics - What role does inertia play in determining how long an egg rotates?


There are two identical eggs boiled egg and raw egg, both are rotated with same angular speed. Which one will come to rest earlier?


I have read this question, but it discuss more about friction and non-friction forces. I want more about role of inertia. If possible, including some calculation.



Answer



If two eggs are given out of which one is hard boiled egg and the other is raw egg. When both of them are allowed to spin on a tabletop, the egg which spins slower must be the raw egg because the liquid inside it tries to get away from the axis of rotation increasing the value of moment of inertia (I). To remain the angular momentum L conserved in absence of external torque i.e. $$ L= I w = constant $$ (where I is moment of inertia & w be the angular velocity), the raw egg will have less angular velocity than the harder one. In this way, I can distinguish two eggs by spinning each on a tabletop.


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