Problem about an sphere.


by ScienceGeek24
Tags: sphere
ScienceGeek24
ScienceGeek24 is offline
#19
Feb29-12, 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?
ScienceGeek24
ScienceGeek24 is offline
#20
Feb29-12, 09:44 PM
P: 158
Ke rot /KEtotal??? Is it like this 1/2mv^2/1/2mv^2+1/5mv^2?
SHISHKABOB
SHISHKABOB is offline
#21
Feb29-12, 09:52 PM
P: 615
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?
ScienceGeek24
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#22
Feb29-12, 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.
SHISHKABOB
SHISHKABOB is offline
#23
Feb29-12, 10:17 PM
P: 615
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?
ScienceGeek24
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#24
Feb29-12, 10:19 PM
P: 158
KE rot
SHISHKABOB
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#25
Feb29-12, 10:20 PM
P: 615
is [itex]\frac{1}{2}mv^{2}[/itex] the rotational kinetic energy?
ScienceGeek24
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#26
Feb29-12, 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!!!
SHISHKABOB
SHISHKABOB is offline
#27
Feb29-12, 10:40 PM
P: 615
no problem, glad I could help :)


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