(adsbygoogle = window.adsbygoogle || []).push({}); A solid cylinder, a solid sphere, and a hoop all of the same mass but different radii, roll without sliding down an inclined plane. The body that gets to the bottom first will invariably be:

the cylinder

the sphere

they all arrive together

not enough information

the hoop

There isn't enough information to solve that problem is there? they all have different radii, so there is no way you can say which one will arrive there the first, because there just isn't enough information right?

Calculate the angular speed of a uniform solid disk about its central symmetry axis if its rotational kinetic energy is 86 J and its moment-of-inertia is 9.0 kgm2.

For this problem i just used the equation that angular KE=1/2Iw^2. I substituted my values for KE and I, and came up with w=4.37 rad/s. is that right?

t is possible for a large star (one greater than 1.4 solar masses) to gravitationally collapse, crushing itself into a tiny neutron star perhaps 40 km in diameter. Suppose such a thing happens to a star which is 2.09e9 m in diameter and spinning at a rate of about once around every 24 days. What would be the spin rate for the resulting neutron star?

For this last problem, i just assumed the ratio of the diameter to the days it takes to make a revolution would be the same. Is that right? or do i need to use some formulas on this one. It seemed incredibly easy the way i did it.

Thanks

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# Rotational Motion

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