1. Student Text Pages 74-80 PRESSURE

2. TOPIC: PRESSURE What does pressure depend on? Pressure is equal to the force exerted on a surface divided by the total area over which the force is exerted.  The word pressure is related to the word press and refers to a force pushing on a surface.  Force and pressure are related, but they are not the same.

4. How do fluids exert pressure? A fluid is a substance that can easily flow. Fluids can change shape. Liquids and gases are both fluids.  Fluids exert pressure against the surfaces they touch.  Fluids are made up of tiny particles called molecules.

5.  In fluids, molecules are constantly moving in all directions. As each molecule collides with a surface, it exerts a force on the surface.  All of the forces exerted by the individual particles in a fluid combine to make up the pressure exerted by the fluid.  Fluid pressure is the force exerted by the fluid divided by the area over which the force is exerted.

6. How does fluid pressure change with elevation and depth?  The air in Earth’s atmosphere is also a fluid. The pressure exerted by this gas is called air pressure or atmospheric pressure.  Air has mass and weight. Each cubic meter of air around you has a mass of about 1 kilogram. In a fluid that is not moving, pressure at any point is exerted equally in all directions. Equal and opposite pressures balance each other.  Atmospheric pressure decreases as elevation increases. At higher elevations, there is less air above and therefore less weight of air to support.

7.  The air pressure at higher elevations is less than the air pressure at lower elevations. Air pressure can be measured with a device called a barometer.  Water pressure increases as depth increases. At greater depths, there is more water above and therefore more weight of water to support.  The water pressure at greater depths is more than the water pressure at lesser depths. The total pressure underwater is a sum of the water pressure plus the air pressure above the water

8. HOMEWORK Chapter 3 Section 1 Page 80 Questions 1-3 all parts. Math Practice 4-5 also. Due 10/9 Newton Scooters Due Oct 20 th.