Physics 10: 1-7 Fluid Mechanics

Homework

Reading Preparation
Key Equations
WebLecture
Study Activity
Chat Preparation Activities
Chapter Quiz
Lab Work

Reading Preparation

Text Reading: Giancoli, Physics - Principles with Applications, Chapter 10: Sections 1-6

Study Points

10.1: Phases of matter are determined by the fixed position of molecules or atoms in a lattice (solid), fluid fixed volumes of incompressible particles bound by their container (liquid), or compressible atoms or molecules that expand to fill their container (gas).
10.2: Density is a derived quantity that tells us how much stuff (mass) is packed into a bit of space (volume). Denser stuff has more mass per unit volume than less dense stuff. As is usual with physicists, we keep a handy rule of thumb measure around: water is is 1 gm/cc (1cc = "one cubic centimeter" = cm³ = 1 ml) = 1 milliliter = 1000 kg/m^3). Specific gravity is the ratio of an object's density to water -- or a unitless way of comparing the density of something to a commonly understood density.
10.3: Pressure is force divided by unit area. When we exert pressure on a fluid, each molecule of the fluid transmits that force to the next molecule. Ultimately, pressure "down" on a fluid surface (or weight of water above on water below) winds up changing direction so that the exerted pressure is exerted evenly in every direction. Pressure from the fluid alone will increase with depth, since as you go deeper, there is more fluid mass above to bear down.
10.4: The most commonly used units of pressure are the atmosphere, bar, and Pascal, which are related as 1 atm = 101.3 kPa = 1.013 * 10^5N/m²; 1 bar = 100 kPa, so it is slightly less than 1 atm. All gauges record pressure above atmospheric pressure. To get absolute pressure, add 1atm to the indicated pressure.
10.5: When you apply pressure down on the surface of the liquid, the independent particles act like spheres. Pressure down is transferred to adjacent particles in all directions equally. For two surfaces of a connected waterway, pressure exerted down on one surface will be transferred to upward pressure on the other surface. Force will be proportional to the areas of the two surfaces.
10.6: Pressure is measured using various gauges (manometer, aneroid gauge, tire gauge, barometer, ).
10.7: Buoyancy is the net force acting on an object in a liquid or gas as a result of gravity (down) and liquid pressure (all directions). Archimedes' principle states that an object that displaces its own mass will float, so objects that are less dense than their surrounding liquid float; objects more dense sink.

Key Equations

Pressure in liquids where density ρ = m/V $P = \frac{F}{A} = \frac{mg}{A} = \frac{(ρ V) g}{A} = \frac{(ρ Ah) g}{A} = ρ gh$
Pascal's Principle: $P_{out} = \frac{F_{out}}{A_{out}} = P_{in} = \frac{F_{in}}{A_{in}} \Rightarrow \frac{F_{in}}{F_{out}} = \frac{A_{out}}{A_{in}}$
Manometer pressure $P = P_{0} + ρ g Δ h$

Web Lecture

Read the following weblecture before chat: Fluid Mechanics and Pressure

Study Activity

Use the simulation below to explore how changing pressure affects fluids. The bubbles on the left allow you to change the configuration of the sink. Move the pressure gauge around to measure pressure at different depths within the sink. Change fluid density and gravitational acceleration with the slide bars. Add or drain water by manipulating the faucet controls.

Physics simulations are the product of the PHET Interactive Simulations project at the University of Colorado, Boulder.

Chat Preparation Activities

Forum question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.

Chapter Quiz

The chapter quiz is not yet due.

Lab Work

If you want lab credit for this course, you must complete at least 18 labs; you may complete more if you are preparing for the AP exam.. One or more lab exercises are posted for each chapter as part of the homework assignment. We will be reviewing lab work at regular intervals, so do not get behind!

Lab Instructions: Buoyancy

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Physics

Chapter 10: 1-7 Assignment