Define pressure. Give its SI unit.
The total force applied per unit area is called pressure.
Mathematically,
Pressure (P) = Force (F) / Area (A)
Its SI unit is pascal (Pa).
Why can't we use water in barometers?
Water cannot be used as a barometric liquid because its density is lower than Mercury. Water's density is 1000 grams per cubic meter. hence it requires a barometer whose height is around 11 meters.