How Does Static Friction Affect Energy Equations in Rolling Motion?

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Homework Help Overview

The discussion revolves around the role of static friction in energy equations related to a uniform sphere rolling down an incline. Participants are exploring how static friction affects the transformation of energy into rotational kinetic energy and its inclusion in energy equations.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning whether static friction should be included in the energy equation and discussing its role in the conversion of energy into rotational kinetic energy. There is uncertainty about the implications of static friction on the total energy equation.

Discussion Status

The discussion is active, with participants sharing insights and referencing previous posts. Some guidance has been offered regarding the nature of static friction and its impact on energy transformations, but there remains a lack of consensus on its inclusion in the energy equations.

Contextual Notes

Participants are navigating assumptions about the effects of static friction and its treatment in energy equations, influenced by differing perspectives from their professor and previous discussions.

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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 ?
 
Last edited:
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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 what's happening here.
 
i think as the friction is static therefore no work is done by it, the work done against friction should not be included
 
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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