Eduqo
General Science›Ch 1: Physics›Pressure and Fluids
Master pressure, buoyancy, surface tension, and viscosity for competitive exams.
Pressure is thrust per unit area measured in Pascals. Fluids transmit pressure equally in all directions according to Pascal's law, while Archimedes principle governs the upward buoyant force on submerged bodies.
Smart Memory Hooks
| Property | SI Unit | Key Formula / Fact |
|---|---|---|
| Pressure | Pascal (Pa) | P = F / A |
| Surface Tension | N/m | T = F / l |
| Viscosity | Poiseuille / Pa·s | Internal friction |
Hydraulic Lift
(Pascal's Law Action)
Pascal's Law Action
Small force on piston lifts heavy cars easily.
Buoyancy
(Upward Liquid Force)
Upward Liquid Force
Iron nail sinks while large steel ship floats.
Capillarity
(Rise in Narrow Tubes)
Rise in Narrow Tubes
Oil rises in lamp wick due to surface tension.
Barometer
(Atmospheric Measure)
Atmospheric Measure
Sudden drop in mercury level indicates approaching storm.
Ice melting in a glass overflows waterWater level remains exactly same
Floating ice displaces its exact weight, so melting does not change water level.
Viscosity of liquids increases with heatViscosity of liquids decreases with heat
Heating weakens intermolecular bonds in liquids making them thinner and less viscous.
Pressure depends on total liquid volumePressure depends only on depth (h)
Hydrostatic pressure is P = h·rho·g, independent of container shape or total volume.
Q1.Which law explains the working of hydraulic brakes in automobiles?
Q2.Why do small water droplets tend to assume a spherical shape?