Fluids
What is a fluid?
A substance that flows and takes the shape of its container.
What is the formula for pressure?
Pressure = Force / Area.
State Pascal’s Principle.
A change in pressure applied to an enclosed fluid is transmitted undiminished throughout the fluid.
What is the formula for density?
Density = Mass / Volume.
Name two examples of fluids.
Water, air.
What is the SI unit of pressure?
Pascal (Pa).
State Archimedes’ Principle.
An object submerged in a fluid experiences an upward force equal to the weight of the displaced fluid.
What is the SI unit of density?
kg/m3.
What states of matter are fluids:
Gas and liquids
Force = 50 N, Area = 2 m². What is the pressure?
25 Pa.
Example of a device using Pascal’s Principle.
Hydraulic press or brakes.
Mass = 10 kg, Volume = 2 m³. Find the density.
5 kg/m3
How do fluids exert pressure on surfaces?
By evenly distributing pressure in all directions.
Why does a sharp knife cut better than a dull one? Use the concept pressure to explain
Smaller area increases pressure.
What does it mean that the object is buoyed up?
That the objects weight is less that the buoyant force of the fluid, so it is pushed upward.
Why does ice float on water?
Ice is less dense than water.
When you begin to exhale:
The diaphragm ________ and moves upward, ________ the volume of the chest cavity.
The lungs have ________ pressure, and outside the mouth there is ________ pressure, so air flows ________ of the lungs.
The diaphragm relaxes and moves upward, decreasing the volume of the chest cavity.
The lungs have high pressure, and outside the mouth there is low pressure, so air flows out of the lungs.
What happens to pressure as depth increases?
It increases due to the added weight of the fluid above.
All fluids exert this upward force.
Buoyant force
You have four objects with the same volume but different densities. In what order (from top to bottom) will the objects settle in the graduated cylinder?
Top: Object B
Object C
Object A
Bottom: Object D