A solid sphere rolls along a flat surface. What percentage of the total energy is the linear kinetic energy? Prove using the formulas for rotational and linear kinetic energy and the
moment of inertia of a solid sphere.

Consider two less-than-desirable options. in the first you are driving 30 mph and crash head-on into an identical car also going 30 mph. in the second option you are driving 30 mph and crash head-on into a stationary brick wall. in neither case does your car bounce off the thing it hits, and the collision time is the same in both cases. which of these two situations would result in the greatest impact force?