-1

If you have two spinning eggs on top of a table, and one of them is hard boiled and the other is raw, how can I analyze this from the perspective of inertia.

I'm asked to include the terms inertia, acceleration and/or velocity, force, exert (this should be used in accordance with which objects are experiencing forces and which aren't), N3L, and at least three FBD to accompany your explanation.

I looked at this question Which body has high moment of inertia (rigid body or soft body)

but I don't know how to talk about acceleration/velocity in this context.

Also I am confused about the FBD.

Any help is appreciated. Thank you

user130306
  • 107

2 Answers2

0

In a hard boiled egg the mass is centered closer to the center of the egg since the yolk is the densest and thus the moment of inertia $\int r^2dm$ is smaller compared to a raw egg, where the dense yolk moves outwards as the centripetal force $F_{cpt} = \frac{mv^2}{r}$ implies a denser material will move outwards when rotating. This means that for the hard boiled egg, almost no energy is lost in having the fluids inside spin and thus gain angular kinetic energy, which is the case for the raw egg. Hope this helps :)

Pim Laeven
  • 78
0

The big difference is that a hard boiled egg is close to the model of a rigid body. When we apply a torque with our hand, its angular velocity increases (while our hand is in contact) by the relation $\tau = I\frac{d\omega}{dt}$, where $\tau$ is the applied torque, $I$ is the moment of inertia, and $\omega$ is angular velocity. After we release it, $\omega$ keeps the same, and decreases gradually due to friction with the surface.

The raw egg is not a rigid body. When we apply a torque, the shell and part of the viscous liquid inside close to the shell will spin accordingly. But most of the internal part is not constrained to spin together. The result is that as soon as we release it, we note that its angular velocity is well smaller than in the former case. The shell is braked by the lower speed internal parts. From that smaller angular velocity it also gradually lose energy until stops.

Claudio Saspinski
  • 16,319