Posted by Ben on Wednesday, October 21, 2009 at 9:29pm.
Hello,
The question is: A solid ball rolls along the floor with a constant linear speed v. Find the fraction of its total kinetic energy that is in the form of rotational kinetic energy about the center of the ball.
Krot/Ktotal = ?
The answer I keep getting is 3/1, but the online homework system says "Your response differs from the correct answer by orders of magnitude.". I know the I for a solid sphere is I = 2/3 mr^2, but I'm still stuck.
Thank you for the help.

Physics (Rotational Kinetic Energy)  bobpursley, Wednesday, October 21, 2009 at 10:23pm
KE=1/2mv^2 + 1/2 *2/3 mr^2*w^2
but v=rw
so w^2=v^2/r^2
KE=1/2mv^2+1/3 mv^2 = 5/6mv^2
what fraction is rotational?
1/3/(5/6)=2/5 or .4 is rotational
check my math.

Physics (Rotational Kinetic Energy)  HeadFull0fZombie, Sunday, February 5, 2012 at 3:14pm
KE=1/2mv^2 + 1/2 *2/5 mr^2*w^2 ..not 2/3 mr^2*w^2 its solid sphere not a hollow sphere.
so the fraction would be 2/7 not 2/5 as the final answer. But bob's approach seems correct.
Answer This Question
Related Questions
 Physics  A solid disk rolls along the floor with a constant linear speed v. (a...
 Physics help  A solid cylinder rolls along the floor. What is the ratio of it's...
 hellllp physics  A solid cylinder rolls along the floor. What is the ratio of ...
 phys  A disk rolls down a slope. It rotational axis is its center of mass. It ...
 PHYSICS  A hollow tube (I = MR2) rolls without slipping along the surface. The ...
 science  A solid spherical ball rolls on table. Ration of its rotational ...
 physics  Question Part Submissions Used A 11.5kg cylinder rolls without ...
 Physics  A rolling barrel with initial velocity 20 m/s encounters a hill 10m ...
 physics  A bowling ball of mass 7.45 kg is rolling at 2.56 m/s along a level ...
 Physics  A bowling ball of mass 7.45 kg is rolling at 2.56 m/s along a level ...
More Related Questions