Equilibrium

A 170cm tall person lies on a light (massless) board which is supported by two scales, one under the feet and one beneath the top of the head. The two scales read, respectively, 31.6kg and 35.1 kg. Where is the center of gravity of this person?

Hydrogen and Oxygen molecules

Hydrogen and Oxygen molecules in a gas sample have the same temperature. This means the hydrogen molecules, on the average have the same? i'm looking for the type of effect concerning kinetic energy and speed.

Volume

a block of wood half as dense as water floats with half its volume above water. A piece of iron is then tied on top so the wood floats with only 1/4 its volume above surface. If the wood and iron are turned over so that the iron is submerged beneath the wood, then the volume of wood above the water surface will be? Why?

Elements

If a pair of helium nuclei are fused together, the result is, and why?

mass/buoyancy

Taking buoyancy of air into account, which has the greater mass? A large block of wood or a smaller block of iron on weighing scales and both having the same weight- 1 ton.