Chapter 3 Review Forces in Fluids

1. Chapter 3 Review Forces in Fluids

2. Pressure refers to a force pushing on a surface • Force and pressure are closely related, but are not the same thing • Pressure deals with force and the area that the force is applied to What is Pressure?

3. Pressure = force/area • Pressure is equal to the force exerted on a surface divided by the total area over which the force is exerted • The larger the surface area the lower the pressure • The smaller the surface area the higher the pressure Calculating Pressure

4. Force is measured in Newtons • Area is measured in square meters (m²) • Pressure is measured in N/ m² • This unit is called a Pascal (Pa) • A more practical unit is the N/cm² Measuring Pressure

5. Fluid- a substance that can easily flow • Liquids and gases • The molecules in a fluid move at all speeds and in all directions • They exert pressure on whatever they touch • All the forces exerted by the individual molecules in a fluid add together to make up the pressure exerted by a fluid Fluids

6. Air pressure- air exerts pressure on you because it has mass • Air pressure is measured with a barometer • Air pressure decreases as elevation increases because there is less air above and therefore less pressure • Water pressure increases as depth increases because as you get deeper there is more weight to support. Fluid Pressure Around You

7. Buoyant force- force that water exerts on submerged objects • It is an upward force and acts against the pull of gravity • Makes objects in water feel lighter Buoyancy

8. The buoyant force of an object is equal to the amount of fluid displaced by the object • An object in water loses some of its weight. The loss of weight is equal to the weight of the liquid displaced by the body. Archimedes Principle

9. Archimedes Principle

10. There is always a downward force on any object in water (this is the weight of the object) • If the weight is greater than the buoyant force the object will sink • If the weight is less than the buoyant force the object will float. Floating and Sinking

11. The amount of matter per unit of volume • How much matter is in a specific space • Density depends on how tightly packed the molecules of the substance are. • An object that is more dense than the fluid in which it is immersed in sinks. • An object that is less dense than the fluid in which it is immersed in floats. Density

12. Density depends upon an objects mass and volume • Density = mass / volume • Mass- the amount of matter in an object • Volume- how much space a three-dimensional object occupies • density is measured in g/cm³ Calculating Density

13. Water has a density of 1 g/cm³ • Anything that has a density greater than 1 will sink in water • Anything that has a density less than 1 will float in water • Any object that is more dense than the fluid it is immersed in will sink. Density and Floating

14. Fluids always flow from areas of high pressure to areas of low pressure • You drink through a straw • Because there is less air in the straw, there is less pressure • The pressure in the cup remains the same • The fluid in the cup then flows into the straw because it is flowing from an area of high pressure to an area of lower pressure High to Low Pressure

15. Air that is moving has lower pressure than air that is not moving. • Bernoulli’s Principle- states that as the speed of a fluid increases, the fluid’s pressure decreases. • Speed goes up, pressure goes down Bernoulli’s Principle

16. Bernoulli’s Principle is one of the reasons that planes can fly. • As the speed traveling over the wings increases, the pressure over the wings decreases • The high pressure under the wings then pushes the plane into the air • Planes also fly because of Newton’s 3rd Law Bernoulli and Flight

17. When force is applied to a confined fluid, an increases its pressure is transmitted equally to all parts. • Force pumps cause a fluid to move from one place to another by increasing the pressure in the fluid. • Forcing the air out creates low pressure, and allows the high pressure fluid to fill the reservoir • Eye dropper, heart, syringe, pipettes, many sea creature’s tentacles Pascal’s Principle