Fluids Introduction Section 0 Lecture 1 Slide 1 Lecture 19 Slide 1 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Physics of Technology PHYS 1800 Lecture 19 Fluids

Introduction Section 0 Lecture 1 Slide 2 Lecture 19 Slide 2 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 PHYSICS OF TECHNOLOGY Spring 2009 Assignment Sheet *Homework Handout

Fluids Introduction Section 0 Lecture 1 Slide 3 Lecture 19 Slide 3 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Physics of Technology PHYS 1800 Lecture 19 Fluids and Thermodynamics An Aside Into Atoms

Fluids Introduction Section 0 Lecture 1 Slide 4 Lecture 19 Slide 4 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Describing Motion and Interactions Position—where you are in space (L or meter) Velocity—how fast position is changing with time (LT -1 or m/s) Acceleration—how fast velocity is changing with time (LT -2 or m/s 2 ) Force— what is required to change to motion of a body (MLT -2 or kg-m/s 2 or N) Inertia (mass)— a measure of the force needed to change the motion of a body (M) Energy—the potential for an object to do work. (ML 2 T -2 or kg m 2 /s 2 or N-m or J) Work is equal to the force applied times the distance moved. W = F d Kinetic Energy is the energy associated with an object’s motion. KE=½ mv 2 Potential Energy is the energy associated with an objects position. Gravitational potential energy PE gravity =mgh Spring potential energy PE apring = -kx Momentum— the potential of an object to induce motion in another object (MLT -1 or kg-m/s) Angular Momentum and Rotational Energy— the equivalent constants of motion for rotation (MT -1 or kg/s) and (MLT -2 or kg m/s 2 or N)

Fluids Introduction Section 0 Lecture 1 Slide 5 Lecture 19 Slide 5 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Look here carefully! A MUCH Closer Look at Collisions

Fluids Introduction Section 0 Lecture 1 Slide 6 Lecture 19 Slide 6 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Bonds between atoms in a compressed solid can be treated as compressed springs. Ultimately the forces come from electrostatic interactions between electrons and protons (and a little quantum mechanics). Compression on an Atomic Scale F spring =-k Δx

Fluids Introduction Section 0 Lecture 1 Slide 7 Lecture 19 Slide 7 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Matter is made up of atoms… The Atomic Theory, a cornerstone of modern science, was proposed by an early Greek thinker, Democritus (c.460 BC - c.370 BC) year later, Feynman deemed this the most important notion in science

Fluids Introduction Section 0 Lecture 1 Slide 8 Lecture 19 Slide 8 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 So begins the quest to see atoms… What is an atom? What do atoms look like? How do atoms move? How big is an atom? How can you see atoms?

Fluids Introduction Section 0 Lecture 1 Slide 9 Lecture 19 Slide 9 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 The case for the existence of atoms… Strong opposition to atomic theory: (1860s) Lord Kelvin The Periodic Table: (1871) Mendeleyev Statistical Mechanics: (1890s) Boltzmann X-Rays: (1895) Röntgen Quantum Theory: (1913) Bohr and Einstein

Fluids Introduction Section 0 Lecture 1 Slide 10 Lecture 19 Slide 10 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 By listing the elements in order of increasing atomic mass, Mendeleev organized the elements into a table with elements of similar properties aligned into columns. This is called the periodic table.

Fluids Introduction Section 0 Lecture 1 Slide 11 Lecture 19 Slide 11 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Trying to see atoms… Optical image (5 X mag) SEM Image (300,000 X mag) STM Image (3,000,000 X mag) STM Image (24,000,000 mag) Magnified images of semiconductor chip.

Fluids Introduction Section 0 Lecture 1 Slide 12 Lecture 19 Slide 12 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Examples of STM images… Pt (100) with vaccancies Si (111) 7x7 reconstructi on Annealed decanethiol film on Au(111) Si (111) with terraces and vaccancies

Fluids Introduction Section 0 Lecture 1 Slide 13 Lecture 19 Slide 13 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Applications of knowledge on the atomic scale… Feynman: “Plenty of room at the bottom” –Inevitability of small –Interface of quantum mechanics with applications

Fluids Introduction Section 0 Lecture 1 Slide 14 Lecture 19 Slide 14 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Moving atoms one at a time…

Fluids Introduction Section 0 Lecture 1 Slide 15 Lecture 19 Slide 15 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Engineering Nanomachines

Fluids Introduction Section 0 Lecture 1 Slide 16 Lecture 19 Slide 16 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Designer Molecules

Fluids Introduction Section 0 Lecture 1 Slide 17 Lecture 19 Slide 17 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009

Fluids Introduction Section 0 Lecture 1 Slide 18 Lecture 19 Slide 18 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 States of Matter

Fluids Introduction Section 0 Lecture 1 Slide 19 Lecture 19 Slide 19 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 States of Matter

Fluids Introduction Section 0 Lecture 1 Slide 20 Lecture 19 Slide 20 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 UNIT TWO Fluids and Heat Understanding the behavior of fluids and thermodynamics is crucial to understanding engines and energy utilization.

Fluids Introduction Section 0 Lecture 1 Slide 21 Lecture 19 Slide 21 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 UNIT TWO Fluids and Heat

Fluids Introduction Section 0 Lecture 1 Slide 22 Lecture 19 Slide 22 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Physics of Technology PHYS 1800 Lecture 19 Fluids Introduction

Fluids Introduction Section 0 Lecture 1 Slide 23 Lecture 19 Slide 23 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Pressure explains... floating objects and moving fluids

Fluids Introduction Section 0 Lecture 1 Slide 24 Lecture 19 Slide 24 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Dennison’s Laws of Fluids When push comes to shove, fluids are just like other stuff. Pascal’s Principle: Pressure extends uniformly in all directions in a fluid. Boyle’s Law: Work on a fluid equals PΔV Bernoulli’s Principle: Conservation of energy for fluids

Fluids Introduction Section 0 Lecture 1 Slide 25 Lecture 19 Slide 25 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Physics of Technology PHYS 1800 Lecture 19 Fluids Pascal’s Principle: Pressure extends uniformly in all directions in a fluid.

Fluids Introduction Section 0 Lecture 1 Slide 26 Lecture 19 Slide 26 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Pressure and Pascal’s Principle Why does a small woman wearing high-heel shoes sink into soft ground more than a large man wearing large shoes?

Fluids Introduction Section 0 Lecture 1 Slide 27 Lecture 19 Slide 27 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Pressure The man weighs more, so he exerts a larger force on the ground. The woman weighs less, but the force she exerts on the ground is spread over a much smaller area. Pressure takes into account both force and the area over which the force is applied. –Pressure is the ratio of the force to the area over which it is applied: –Units: 1 N/m 2 = 1 Pa (pascal) –Pressure is the quantity that determines whether the soil will yield.

Fluids Introduction Section 0 Lecture 1 Slide 28 Lecture 19 Slide 28 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Pressure and Force Fluids don’t support unconfined forces So consider a piston in a confined cylinder Force is spread over the full area of the piston We call this pressure, P=F/A (ML -1 T -2 or kg/m-s 2 or N/m 2 or Pa) Work is ΔW=F Δd or in the case of fluids ΔW = (P A) Δd = P ΔV

Fluids Introduction Section 0 Lecture 1 Slide 29 Lecture 19 Slide 29 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Pascal’s Principle What happens inside a fluid when pressure is exerted on it? Does pressure have a direction? Does it transmit a force to the walls or bottom of a container?

Fluids Introduction Section 0 Lecture 1 Slide 30 Lecture 19 Slide 30 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Pascal’s Principle Fluid pushes outward uniformly in all directions when compressed. Any increase in pressure is transmitted uniformly throughout the fluid. Pressure exerted on a piston extends uniformly throughout the fluid, causing it to push outward with equal force per unit area on the walls and the bottom of the cylinder. This is the basis of Pascal’s Principle: –Any change in the pressure of a fluid is transmitted uniformly in all directions throughout the fluid.

Fluids Introduction Section 0 Lecture 1 Slide 31 Lecture 19 Slide 31 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Pascal’s Principle for Gases Gas molecules lack strong interactions. Pressure is understood as resulting from momentum transfer to the container walls through unbalanced collisions Pressing on one surface adds force and hence imparts impulse to the gas That impulse is taken up as added collisons (pressure) on other surfaces The random nature of the motion of gas particles assures that the force is distributed evenly to all surfaces For fixed walls, a decrease in V results in an increase in P For expandable walls (like a balloon) the volume “appears elsewhere to make up for the lost volume

Fluids Introduction Section 0 Lecture 1 Slide 32 Lecture 19 Slide 32 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Pascal’s Principle for Liquids Liquid molecules have strong interactions. Liquids do not compress much Pressure is understood as resulting from momentum transfer to the container walls through unbalanced spring forces Pressing on one surface adds force that is transferred to other springs The network nature of the forces on the particles assures that the force is distributed evenly to all surfaces For expandable walls (like a balloon) the volume “appears elsewhere to make up for the lost volume For fixed walls, a small decrease in V (a compression) results in a large increase in P For solids, you can think of the strong forces holding the atoms in there equilibrium positions, equivalent to fixed walls

Fluids Introduction Section 0 Lecture 1 Slide 33 Lecture 19 Slide 33 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Physics of Technology Next Lab/Demo: Rotational Motion Fluids Thursday 1:30-2:45 ESLC 46 Ch 8 and 9 Next Class: Monday 10:30-11:20 BUS 318 room Read Ch 9