decreases linearly with elevation

remains constant

varies in the same way as the density

increases exponentially with elevation

(a) it is the best liquid

(b) the height of barometer will be less

(c) its vapour pressure is so low that it may be neglected

both (b) and (c)

pressure in pipes, channels etc.

atmospheric pressure

very low pressure

difference of pressure between two points

Venturimeter

Orifice plate

hot wire anemometer

pitot tube.

Venturimeter

pitot tube

hot wire anemometer

rotameter