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Problem about an sphere.by ScienceGeek24
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#19
Feb2912, 09:43 PM

P: 158

LOL good question. Total KE?? But what is the total kineteci eenrgy here is it KE rot+ KE trans?? so is 1/2mv^2/1/2mv^2+1/5mv^2?



#20
Feb2912, 09:44 PM

P: 158

Ke rot /KEtotal??? Is it like this 1/2mv^2/1/2mv^2+1/5mv^2?



#21
Feb2912, 09:52 PM

P: 614

it actually tells you in the question ;)
"What fraction of its kinetic energy is rotational?" in other words: Which part of the total kinetic energy is rotational kinetic energy? Thus, we are looking for the rotational part of the total kinetic energy. if you have [itex]\frac{\frac{1}{2}mv^{2}}{\frac{1}{2}mv^{2}+\frac{1}{5}mv^{2}}[/itex] then what is that representing? 


#22
Feb2912, 10:11 PM

P: 158

a fraction .... but if the m's and v's cancel they give 5/7 not 2/7 i give up.



#23
Feb2912, 10:17 PM

P: 614

wait! don't give up! we're almost there :D
what I was just asking was what's on top? Is it rotational kinetic energy or tangential kinetic energy? 


#24
Feb2912, 10:19 PM

P: 158

KE rot



#25
Feb2912, 10:20 PM

P: 614

is [itex]\frac{1}{2}mv^{2}[/itex] the rotational kinetic energy?



#26
Feb2912, 10:36 PM

P: 158

ahh tangential is 1/2mv^2 my bad KE rot is 1/5Iw^2? ARRGHHH JFC!!! ROFLMAO!!! I though KE rot was 1/2mv^2 when is 1/5mv^2 now it does give 2/7!! :P Thank you so much for your patients dude!!!



#27
Feb2912, 10:40 PM

P: 614

no problem, glad I could help :)



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