Aclimber pulls down on a rope causing his body to rise up with the rope? which law of motion is it?

This would be called the law of action-reaction. This states that every action will have an equal and opposite reaction. The action in the example is pulling down on the rope. The opposite and equal reaction is the climers body moving upward. The same law can be applied to a rocket. The action is the engines pushing down and the reaction is the rocket going up. :D

The density of the block of iron is lees than the density of mercury but the density of the block of iron is greater than the density of water