Sunday

October 26, 2014

October 26, 2014

Posted by **Ben** on Wednesday, October 21, 2009 at 9:29pm.

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 10:23pmKE=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 3:14pmKE=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 ...

physics - A ball attached to the end of a string is whirled on a horizontal ...

PHYSICS - A hollow tube (I = MR2) rolls without slipping along the surface. The ...

physics help please 1!! - A 1.27 kg hoop with a radius of 10.0 cm rolls without ...

phys - A disk rolls down a slope. It rotational axis is its center of mass. It ...

physics - a bowling ball has a mass of 8kg. if it rolls down the alley, without ...

Physics- PLEASE HELP - A 10.0 kg cylinder rolls without slipping on a rough ...

physics - An experimental flywheel, used to store energy and replace an ...