Sphere on ramp kinetic energy

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Homework Statement


This question isn't for a specific problem. Just knowledge to approach a series of problems.
It concerns a problem where a uniform sphere rolls smoothly down a ramp at incline theta. There is a static frictional force on the ramp. I can go on to find acceleration I am just unsure as to the role of the force of friction in the energy equations.

Homework Equations


E=KE+U
KE=1/2mv^2
KE=1/2Iw^2

The Attempt at a Solution


I'm just Unsure as to whether The force of static friction should be included in the original energy equation or not:

mgh = 1/2mv^2 + 1/2Iw^2 + Fx ???
 
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Answers and Replies

  • #2
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Did some digging and found an old post

"Even though no work is done by friction, it does cause energy to be transformed into rotational KE. In the ideal case, there would be no loss in mechanical energy. (Of course, in real life there is rolling friction, deformation, etc., which does dissipate mechanical energy.)"

So is this saying that friction creates the rotational kinetic energy? Do I need to include it in the Total Energy equation then as Fx? Still at a bit of a loss. Don't know why I'm having such a hard time picturing whats happening here.
 
  • #3
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i think as the friction is static therfore no work is done by it, the work done against friction should not be included
 
  • #4
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Thanks for the response. That's what i thought but something my professor told me got me thinking i had to include it in the equation for total energy.
 

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