When a person uses deodorant spray, the other person standing at a distance would hear the sound of spraying first and the fragrance of spray would reach him later. Why so?

Two persons having the same mass are standing on ice-skates some distance apart on a frictionless surface.a rope is fastened around the body of a person,the other end of which si in the hand of the second person.What would happen if the second person pulls the rope?

A person can not see clearly objects beyond a distance of 1.2 m.Name the defect of vision he is suffering from.What would be the power of correcting lens used to restore proper vision?

Deep sea divers have been using the compressed air containing N_2 in addition to O_2 for breathing. When the sea divers breathes in compressed air at a depth, more N_2 dissolves in the blood and other body fluids than would dissolved at the surface because the pressure at the depth is far greater than surface atmospherice p ressure. when the diver comes towards the surface, the pressure decreases and N_2 comes out of the body quickly forming bubbles in the stream which restrict blood flow and affect the transmission of nerve impuses. this results into a condition called 'the bends' which is dangerous and painful. To avoid this condition, professionals now use air diluted with helium. As a student of chemistry, can you analyse as to why helium is used?