1. P RESSURE & D ENSITY Forces in Fluids

2. Pressure is the amount of force per unit area applied to an object’s surface. Pressure = Force / Area

3. P RESSURE Example: A surfer applies a force of 645 N on the water. The area of the surfboard is 1.5 meters squared. What is the pressure applied? P = F/A P = 645 N / 1.5 meters 2 P = 430 Pa

4. Surface area increases = Pressure decreases Surface area decreases = Pressure increases

5. Atmospheric Pressure – the ratio of weight of all the air above you to your surface area.  Decreases as you move up in elevation Underwater pressure  Increases as you move down

6. D ENSITY Density = Mass / Volume Example: A box has a mass of 10 kg and a volume of 2 cubic centimeters. What is the density? D = M/V D = 10 kg / 2 cm 3 D = 5 kg/cubic cm 3

7. Water has a density of 1.  Objects float if they have a density less than 1  Objects sink if they have a density more than 1.

8. B UOYANCY A buoyant force is an upward force applied by a fluid on an object in the fluid. Archimedes’ Principle states that the weight of the fluid that an object displaces is equal to the buoyant force acting on the object.

9. B UOYANT F ORCE & W EIGHT  Weight greater than buoyant force = sinks  Weight less than buoyant force = floats