If carbon-14 has a half life cycle of 5700 years, how many years have past if only 12.5% of it remain in an ancient sample?

Aperson stands on a platform, initially at rest, that can rotate freely without friction. the moment of inertia of the person plus the platform is ip. the person holds a spinning bicycle wheel with its axis horizontal. the wheel has moment of inertia iw and angular velocity ωw. take the ωw direction counterclockwise when viewed from above. part a what will be the angular velocity ωp of the platform if the person moves the axis of the wheel so that it points vertically upward?

What is the most useful equation for electric power?

Which lists the pairs of plates in order from least to greatest in terms of the work done to move the electron?