quantumfoam Posted October 15, 2012 Posted October 15, 2012 Hello guys! Now this is not a homework question, but it may sound like one. If a uniform sized and massed sphere was spinning in space away from any source of forces that could affect it, wouldn't the only forces that act on it are the centripetal and centrifugal? And if this sphere had elasticity, wouldn't the force that is stretching the sphere be either centripetal of centrifugal force? Now I am not including its gravitational force on purpose. Its gravitational field can be negligible. I also know that the centrifugal force is not a real force, but it is useful for explaining some phenomena. I'm using classical mechanics. The sphere will not be spinning at relativistic speeds. Well, mathematically, I figured that if the centripetal and centrifugal forces are the sources of deformation of stretching of the sphere, then by using Hooke's Law we find that mwv=-kx where mwv is the centripetal or centrifugal force magnitude and -kx is Hooke's Law. Is this right? Or am I forgetting something? I would really appreciate anyone's help. My extremely inferior mind is not sure of itself. ):
mathematic Posted October 15, 2012 Posted October 15, 2012 (edited) A short answer is look at the earth. It bulges at the equator because it is spinning. It is due to "centrifugal force". Edited October 15, 2012 by mathematic
quantumfoam Posted October 15, 2012 Author Posted October 15, 2012 I know that but was my mathematics right?
swansont Posted October 17, 2012 Posted October 17, 2012 If the elasticity of the material is the restoring force, then the source of the centripetal force will be from the elasticity. If it follows Hooke's law, then that's what you use.
swansont Posted October 18, 2012 Posted October 18, 2012 Isn't gravity the restoring force? Gravity is negligible in this problem, as per the OP.
mathematic Posted October 18, 2012 Posted October 18, 2012 Gravity is negligible in this problem, as per the OP. I am a little confused. The gas giants spin and the restoring force must be gravity, since the material is not solid.
swansont Posted October 19, 2012 Posted October 19, 2012 I am a little confused. The gas giants spin and the restoring force must be gravity, since the material is not solid. The OP discusses an elastic ball, not a gas giant.
quantumfoam Posted October 20, 2012 Author Posted October 20, 2012 Would I be able to describe the entire situation of our elastic spinning sphere using tensors?
mathematic Posted October 20, 2012 Posted October 20, 2012 The OP discusses an elastic ball, not a gas giant. I misunderstood. I thought he was asking about real planets.
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