Chapter 11 Forces in Fluids Section 1: Pressure Members : Briglio, Mason Dai, Ying Leiva, Christian Martin, Kimberly Tieu, Sammie Tran, Cindy Wang, JunZheng Wong, Westley Yin, Cheng Zeng, Johnny

Introduction During this presentation we will be explaining to you thoroughly on what pressure is. To start off we shall give you a basic definition of pressure. Pressure is the force per unit area applied to an object. Although this is the definition, there are many different types of pressure. Such as gauge pressure, atmospheric pressure, ambient pressure, etc. There is also a formula for pressure. But we will keep that for another slide. Also, there are a SI units for pressure. One of them is Pascal. But we shall talk about this later on in this presentation. We now conclude our introduction and we hope that you will enjoy and learn from our presentation.

Objective To teach the class about pressure and area. We will also teach about the formulas for pressure, the amount of pressure you exert, how atmospheric pressure decreases as your elevation increases, and how water pressure increases as depth increases.

Main Idea Pressure is the force per unit area applied to an object in a direction perpendicular to the surface. Pressure is a scalar quantity and has SI units of Pascal.

Key Terms -Pressure: Pressure is equal to the force exerted on a surface divided by the total area over which the force is exerted -Pascal: A unit of pressure equal to 1 Newton per square meter -Fluid: A fluid is a material that can easily flow -Barometer: An instrument used to measure atmospheric pressure

-P-Pressure is the force exerted on a surface divided by the total area over which the force is exerted - One way to calculate pressure is to follow the formula: Pressure = Force Area -T-The larger the area over which the force is distributed, the less pressure is exerted What Is Pressure?

Fluid Pressure -A fluid is a material that can easily flow -Fluids exert pressure -A fluid can change shape -Examples of fluid: water, oil, air, and helium -Particles in fluid constantly move in all directions -The particles collide with each other with any surface where they meet - As each particle of a fluid collides with a surface, it exerts a force on the surface -Air is a mixture of gases that makes up Earth’s atmosphere -These gases press down on everything on Earth’s surface -The air has weight -The weight of the air is the force that produces air pressure, or atmospheric pressure -In a stationary fluid, pressure at a given point is exerted equally in all directions -Balanced pressure explain why the tremendous air pressure pushing on you from all sides does not crush you -Body contains fluids that exert outward pressure -Cells and blood vessels contain liquids

Variations in Fluid Pressure -The “popping” in your ears is caused by changing air pressure -At higher elevation, there is less air pressure -When the air pressure outside your body decreases, the air pressure inside also decreases, but more slowly -The deeper you swim underwater, the greater pressure you feel -Water pressure is a result of weight of the water above a particular point -In the deepest parts of the ocean, the pressure is more than 1,000 times the air pressure you experience everyday -A barometer can be used to measure the atmospheric pressure -Rapidly decreasing atmospheric pressure usually means a storm is on its way -Increasing pressure us often a sign of fair weather -Standard atmospheric pressure at sea level may be reported as 760 millimeters of mercury, which is about the same as 101,300 Pa

Example #1 The amount of pressure depends on the area over which a force is distributed. The amount of pressure you exert depends on the area over which you exert a force.

Example #2 An example of unbalanced pressure: - The can contains air. The air pressure pushing out balances the air pressure pushing in. - But when the air is removed from the can, there is no longer the same pressure pushing out. The greater air pressure outside the can crushes the can. - A vacuum pump removes the air from a metal can. The unbalanced air pressure produces dramatic results in a few moments.

Formula Force: measured in newtons ( N ) Area: measured in square meters ( m 2 ) Because force is divided by area, the SI unit of pressure should be ( N/m 2 ). This unit of pressure if also named Pascal ( Pa ) : N/m 2 = 1 Pa. This is named after the French mathematics Blaise Pascal.