How much kinetic energy is in a punch thrown at 30 m/s? The fist and arm weighs 6 lbs. (1 lb= 2.2 kg)

You throw a small rock straight up from the edge of a highway bridge that crosses a river. the rock passes you on its way down, 7.00 s after it was thrown. what is the speed of the rock just before it reaches the water 28.0 m below the point where the rock left your hand? ignore air resistance.

In a classical model of the hydrogen atom, the electron moves around the proton in a circular orbit of radius 0.053 nm. what is the electron's orbital frequency? what is the effective current of the electron?

How does the entropy of steam compare to the entropy of ice?