9th grade in the Physics First Curriculum What is the Physics First program? INTRODUCING FORCES Physics First is a national movement to teach a year-long Physics course in 9th grade Jaime Horton In Missouri, MO-DESE has funded a partnership Amy Scroggins led by Columbia Public Schools and Univ. of Carthage R-9 School District Meera Chandrasekhar Missouri-Columbia to develop curriculum and conduct professional development (PD) Dorina Kosztin Department of Physics and Astronomy The first summer of PD was conducted in 2006 University of Missouri, Columbia for 60 teachers, who will return in 2007 and 2008 Support: Missouri Department of Elementary and A smaller protégé class of 22 was accepted for Secondary Education 2007 and 2008. Math-Science Partnership Grant www.physicsfirstmo.org Curriculum Students’ Beliefs about Forces Year 1: Uniform and Accelerated Motion, Forces, Only animate objects can exert forces and Newton’s Laws Forces are seen as merely influences on an Year 2: Motion in 2D, Energy, Momentum, and object’s motion, not as forces Electricity Impetus theory – e.g., force of throw travels with Year 3: Electromagnetism, Waves, and Heat ball Pedagogy - based on Modeling, Inquiry & 5E Forces are viewed from the perspective of the Year-long follow-up and support applier, rather than that of the object Tension/Normal forces not well understood Today - parts of the Unit 3: Introducing Forces 1 Learning Objectives Big Understandings and Skills A force is an interaction between two objects (an agent Big Understandings: and a receiver) A force is a push or a pull on an object. Identify forces acting on an object in terms of a receiver, A force is a vector - has both amount (magnitude) and direction. one or more agents, effects and direction A force requires an agent (something does the pushing or Draw a force diagram for the object/receiver pulling). Describe the parameters that can change/affect amount A force is either a contact force or a long-range force (gravity is of the force the only long-range force in this unit). State whether resultant force causes the velocity of the The force acting on an object may be the sum of several forces object to be constant or changing (net force). Determine if forces acting on an object are Skills: balanced/unbalanced Identifying forces Figuring out net force (GLEs: 2.2.A.a, 2.2.B.c, 2.2.D.c, 2.2.D.d, 2.2.D.e) In this unit…. Part 1: ID different forces, their agents, receivers, effects Investigate in more detail: normal forces, gravity, friction and elastic forces Activity: Exerting Forces Part 2: Forces as vectors Work with several forces acting on an object draw force diagrams understand graphically how forces balance if forces do not balance, obtain the net force 2 Pre-lab questions Exerting Forces - Directions How do you know when you exert a force? At each station, create a chart with the following: Could you make a list of the different forces you A picture or diagram showing each situation exerted in the last five minutes? Are there any forces exerted? How strong a force do you think you can exert? What/who is applying the force? What do you think is meant by the term “force”? What object receives the force? What are some things that can happen to an What effect does the force have on the object? object when a force acts on it? What do you think is the name of the force demonstrated at this station? Two General Categories of Forces Contact forces – those that require the agent that causes the force to be in contact with the object. Examples: pushing, pulling, squeezing, Whiteboard feedback from Exerting Forces activity stretching, ….. Field Forces – those that act at a distance. Examples: gravity, magnetism, electricity 3 Examples: Contact and Field forces The Four Forces of Nature Many forces on the macroscopic level, such as Gravity: Tension: brings the skier down Holds the pot gravity, friction, elastic, electric, push and pull, centripetal forces The origins of these forces can be traced to only four fundamental forces: Gravity Normal: Friction: Electromagnetic holds the owl up slows you down Strong Weak The Four Forces of Nature-2 Analyzing Forces Gravity – due to the mass of objects. Holds A force is produced by an agent stars, planets together. A force acts on an object – the receiver Electromagnetic – due to the charge on objects. The force causes something to happen – the Responsible for binding of atoms and molecules. effect Strong – holds neutrons and protons together, restricted to the nuclei of atoms Weak – short-range force, produces instability in certain nuclei 4 Analyzing forces – Example 1 Weight of boy (gravity): Friction Agent – earth; Receiver – boy; Effect – boy slides downward. Activity: Friction: Identifying and Drawing Forces Agent – surface of slide and Practice III.1 Force Challenge A-D boy’s skin and clothes; Receiver – lower surface of girl’s body; Effect – girl’s downward slide is slowed down. Weight Forces studied in unit Four forces are studied in some detail: Normal force Gravitational force (lab) Friction (lab) Activity: Elastic force (lab) The Strength of Weight Lab 5 Activity: The Strength of Elastic Force Lab Activity: The Strength of Elastic Force Lab Experimental Results Experimental Results Added Rubber Added Mass Spring Band Bungee Mass Big spring Little Spring (g) (cm) (cm) (cm) (g) (cm) (cm) 0 54.1 35.9 55.1 0 15.5 13.9 100 56.4 38.2 55.7 10 19.5 15.9 200 60.5 41.5 56.1 20 23.7 17.9 300 64.4 46.5 56.5 30 27.7 19.8 400 68.6 53.6 57 40 31.8 21.7 500 72.8 57.7 57.5 50 35.9 23.7 600 76.8 61.2 58.8 60 39.8 25.6 700 81.2 63.3 61 70 43.5 27.6 800 85.4 64.5 63.5 80 47.7 29.7 900 89.6 65.3 65.6 90 51.5 31.4 1000 94 65.5 68.3 100 55 33.5 6 ) g ( s s a M Stretch (cm) Conclusions Drawing forces Force is directly proportional to stretch Normal Slope of F vs stretch represents the strength of the spring, k. Weight Normal rise F k = slope = = e Weight run !x [F] N [k]= = Normal [!x] m Weight 7 Force Diagrams - Example 1 Force Diagrams - Example 2 4. Identify contact forces where 1. Picture 2. Identify System system touches the closed curve. 7. Force Diagram 5. Normal force,F N FN 3. Closed curve 6. Force of gravity, F around system G FG Force Diagrams - Example 2 Force Diagrams - Example 2 8 Force Diagrams - Example 2 Force Diagrams - Example 2 Force Diagrams - Example 2 Force Diagrams - Example 3 2-3. Define system and draw 7. Force closed curve around it. 1. Picture 4. Contact forces where system diagram touches curve 7. Force Diagram FN 5. (a)Normal 5. (b) Force FN Tension FT FN FT FT Ff 6. Force of FG gravity FG FG 9 Next steps... This unit then goes on to activities that connect Contact info force to motion [email protected] The next unit is Newton’s Laws [email protected] www.physicsfirstmo.org If you are a 9th grade teacher and are interested in this program, please do contact us - we plan to seek funding for a new cycle. 10.