• Support PF! Buy your school textbooks, materials and every day products via PF Here!

Sphere on ramp kinetic energy

  • Thread starter 240rr
  • Start date
1. The problem statement, all variables and given/known data
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.

2. Relevant equations
E=KE+U
KE=1/2mv^2
KE=1/2Iw^2

3. 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:
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.
 
i think as the friction is static therfore 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.
 

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top