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Transcript
Physics of Technology PHYS 1800 Lecture 18 Introduction Review for Test 2 Section 0 Lecture 1 Slide 1 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 1 PHYSICS OF TECHNOLOGY Spring 2009 Assignment Sheet Date Day Lecture Chapter Jan 5 M Class Admin: Intro.Physics Phenomena 1 6 T Problem solving and math App. B, C 7 W Units, Scalars, Vectors, 1 9 F* Speed and Velocity 2 Jan 12 M Acceleration 2 14 W Free Falling Objects 3 16 F* Projectile Motion 3 Jan 19 M Martin Luther King No Class 21 W Newton’s Laws 4 23 F* Mass and Weight 4 Jan 26 M Motion with Friction 4 28 W Review 1-4 1-4 29 Th Test 1 30 F Circular Motion 5 Feb 2 M Planetary Motion and Gravity 5 4 W Energy 6 6 F* Harmonic Motion 6 Feb 9 M Momentum 7 11 W Impulse and Collisions 7 13Introduction F* Rotational 8 Section 0 Motion Lecture 1 Slide 2 Feb 16 M Presidents Day No Class 17 Tu Angular Momentum (Virtual Monday) 8 18 W Review 5-8 19 5-8 H Test 2 INTRODUCTION TO Modern Physics PHYX 2710 20 F* Static Fluids, Pressure 9 Fall 2004 Feb 23 M Flotation 9 25 W Fluids in Motion 9 27 F* Temperature and Heat 10 Mar 2 M First Law of Thermodynamics 10 Physics of Technology—PHYS 1800 4 W Spring 2009Heat flow and Greenhouse Effect Review 10 *Homework Handout 6 F* Climate Change - Homework Due - 1 2 3 4 5 - 6 Lecture 17 Slide 2 7 Physics of Technology PHYS 1800 Lecture 8 Circular Motion Gravitational Forces Conservation of Energy Conservation of Momentum Conservation of Angular Momentum Introduction Section 0 Lecture 1 Slide 3 Introduction and Review INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 3 Notes on Test 1. Covers Chapters 5-8 (Chapter 8 only qualitatively) 2. ~8 short answer problems or questions (5 point each) 3. 3 Numerical problems based heavily on the material from the homework and Lab/Demo sessions (20 points each). One problem each from Chapters 5, 6 and 7. 4. You will have a formula sheet just like the one in Introduction Section 0 Lecture 1 Slide 4 the handout. 5. Test is Thursday February 19 1:30-2:45 in ESLC 46. INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 4 What Do We Need To Measure? • What is the minimum about things we need to know? • Where things are—a length, L • When things are there—a time, T • How thing interact with gravity—a mass, M • How things interact with E&M—a charge, Q Introduction Section 0 Lecture 1 Slide 5 • How thing inter act with weak nuclear force • How things interact with strong nuclear force INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 5 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/s2) Force— what is required to change to motion of a body (MLT-2 or kg-m/s2 or N) Energy—the potential for an object to do work. (ML2T-2 or kg m2/s2 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 mv2 Potenital Energy is the energy associated with an objects position. Gravitational potential energy PEgravity=mgh Spring potential energy PEapring= -kx Introduction Section 0 Lecture 1 Slide 6 In this chapter we will develop the concept of…MOMENTUM…and and its associated law of Conservation of Momentum and apply this to collisions. INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 6 Newton’s Laws in Review • 1st Law —a special case of the 2nd Law for statics, with a=0 or Fnet=0 • An objects velocity remains unchanged, unless a force acts on the object. • 2nd Law (and 1st Law)—How motion of a object is effected by a force. – The acceleration of an object is directly proportional to the magnitude of the imposed force and inversely proportional to the mass of the object. The acceleration is the same direction as that of the imposed force. F ma units : 1 newton = 1 N = 1 kg m s2 • Introduction Section 0 Lecture 1 Slide 7 3rd Law —Forces come from interactions with other objects. • For every action (force), there is an equal but opposite reaction (force). INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 7 Central Forces and Gravity Introduction Section 0 Lecture 1 Slide 8 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 8 The Math Approach • We are going to explore a different kind of central force that is no longer constant, but is proportional to 1/r2. ag k/r2 v f v0 at or a v f vo t 1 2 vo vo v f vo d t t v0t at 2 2 2 2 We will take a pragmatic approach (hindsight is 20-20!) Introduction Section 0 Lecture 1 Slide 9 We simply replace the force of the “string” with the force of gravity INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Tstring Fgravity k Review r2 Lecture 17 Slide 9 Newton’s Law of Universal Gravitation • Newton recognized the similarity between the motion of a projectile on Earth and the orbit of the moon. • If a projectile is fired with enough velocity, it could fall towards Earth but never reach the surface. • The projectile would be in orbit. • Newton’s law of universal gravitation says the gravitational force between two objects is proportional to the mass of each object, and inversely proportional to the square of the distance between the two objects. Introduction • Section 0 Lecture 1 Slide 10 G is the Universal gravitational constant G. Fgravity INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Gm1m2 r2 Lecture 17 Slide 10 Energy Introduction Section 0 Lecture 1 Slide 11 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 11 Mechanical Advantage and Simple Machines • The mechanical advantage of a simple machine is the ratio of the output force to the input force. – For the pulley example, the mechanical advantage is 2. • Work is equal to the force applied times the distance moved. – Work = Force x Distance: W=Fd – Work output = Work input • units: 1 joule (J) = 1 Nm= 1 kg m2 / s2 [ML2T-2] Introduction Section 0 Lecture 1 Slide 12 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 12 Conservation of Energy Energy Energy: The potential to do work. Conservation of Energy: The total energy of a closed system remains constant. – Energy can be converted from one form to another. – Not all forms of energy can be fully recovered. Introduction Section 0 Lecture 1 Slide 13 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Time Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 13 The horizontal position x of the mass on the spring is plotted against time as the mass moves back and forth. • The period T is the time taken for one complete cycle. • The frequency f is the number of cycles per unit time. F=1/T • The amplitude is Introduction Section 0 the maximum distance from equilibrium. Lecture 1 Slide 14 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 X(t) = A sin (2π f t) Review Lecture 17 Slide 14 Impulse-Momentum Principles Introduction Section 0 Lecture 1 Slide 15 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 15 Momentum and Impulse • Multiply both sides of Newton’s second law by the time interval over which the force acts: • The left side of the equation is impulse, the (average) force acting on an object multiplied by the time interval over which the force acts. v Fnet ma m t Fnet t mv • How a force changes the motion of an object depends on both the size of the force and how long the force acts. • The right side of the equation is the change in the momentum of the object. Introduction Section 0 Lecture 1 Slide 16 • The momentum of the object is the mass of the object times its velocity. p mv INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 16 Impulse-Momentum Principle The impulse acting on an object produces a change in momentum of the object that is equal in both magnitude and direction to the impulse. impulse = change in momentum = p In analogy, Introduction Section 0 Lecture 1 work INTRODUCTION TO Modern Physics PHYX 2710 Slide 17 = change in energy = ΔE Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 17 Rotational Motion and Forces Introduction Section 0 Lecture 1 Slide 18 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 18 Formulas We Know and Love Introduction Section 0 Lecture 1 Slide 19 INTRODUCTION TO Modern Physics PHYX 2710 Fall 2004 Physics of Technology—PHYS 1800 Spring 2009 Review Lecture 17 Slide 19