In which type of wave does the medium move parallel to the direction of the energy transport?

An object weighs 40n in air, weighs 20n when submerged in water and 30n when submerged in a liquid of unknown density. what is the density of the liquid?

1. how to locate the image in converging(concave) mirror and diverging (convex) mirror with salt. 2. how to locate the image in a converging (convex) lens and diverging (concave) lens with salt.

Acamcorder has a power rating of 20 watts. if the output voltage from its battery is 9 volts, what current does it use?