Problem about an sphere.

SHISHKABOB

a fraction is a part of a whole, right? So which part of what whole are we looking for?

ScienceGeek24

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

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

SHISHKABOB

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

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

SHISHKABOB

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

KE rot

SHISHKABOB

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

ScienceGeek24

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

no problem, glad I could help :)