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This chapter introduces the concept of acceleration and its equation, explores position-time and velocity-time graphs, and covers acceleration due to gravity. Practice problems and essential questions are included.
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Chapter 3: Acceleration Physics: Principles and Problems
Agenda • ACT/PSAE practice • Intro to acceleration • What does it mean in common language? • What does it mean to a physicist? (That’s you!) • First equation of acceleration • A = v/t • Standard unit for acceleration: m/s^2 • Example Problem • HW: Acceleration WS #1 • Be sure to convert km/h to m/s!
Essential Questions for the Chapter • What is acceleration? When am I accelerating? • Is acceleration a scalar or vector? • How do I solve a physics problem involving Acceleration? • What does a position-time graph of acceleration look like? • What are velocity-time graphs, and how can I find distance travelled and instantaneous acceleration
Acceleration • What does it mean to you in common conversation? • What is the book’s definition? • “Deceleration” is just acceleration in a negative direction
Example Problem • ______ is riding their bike to school. They
Bellringer • 1. You run the 100 meter dash with an average velocity of 8 m/s. How long does it take you to finish? • 2. Make a position-time graph of the following motion diagram: (Line shows meters) • (Hint: how long did it take to go 10 meters?) • 3. If your car can accelerate from rest to 20 m/s in 4 seconds, what is its acceleration?
Bellringer When you fall, do you fall at a constant rate or accelerated rate? How do you know? Use complete sentences (UCS).
Bellringer • Is acceleration a scalar or vector? How do you know? Use complete sentences (UCS).
Agenda 9/15 • Collect Reaction Time Lab • Bellringer • Introduce Acceleration Equation #2: • THE MONSTER! • df = ½ a* t^2 + Vyi * t + di • Example Problem • Acceleration WS #2 • Due Wednesday • EQ: How does acceleration affect distance travelled?
Acceleration • Already know: Acceleration = (Vf – Vi) / t • How do we find displacement? • Df = ½ a * (t)^2 + Vi * t + Di • Df = • a = • t = • Vi = • Di = • What kind of equation/relationship/graph is this?
Bellringer • If your car can accelerate at 5 m/s2, how long will it take the car to accelerate from 10 m/s to 25 m/s?
Agenda • Bellringer • Graphing Assignment • Acceleration WS 2 pushed back to Thursday (for this class only)
Bellringer • Draw a position time graph of the following: • 1. An object travelling at a constant velocity • 2. An object that is not moving (start it at a position other than zero so we can see the line) • 3. An object travelling that changes its velocity. • Make sure to label your axes!
Agenda • Bellringer • Average Velocity WS corrections [10 min] • Reading Guide 3.1-3.2 [10 min] • Finish Acceleration ws 2
Agenda 9/21 • Collect Acceleration WS 2 • Lab: Speed Freaks 2.0 • Go to the FOOTBALL FIELD! • Essential Questions: • What does acceleration look and feel like? • How do we calculate speed and acceleration?
9/25 Agenda • Introduce ‘g’ • -9.8 m/s^2 • Hang Time Lab • Finish by tomorrow first thing! • Essential Questions: • Does gravity pull things down at a constant velocity or accelerated? At what rate? • How does gravity affect how I jump?
9/26 Agenda • Collect Ch 2.2 Reading Guide • Learn Breaking Distance Equation • Problem Reading Trainer • Accelerated Problem Poster Project • Buy a poster this weekend. In fact, buy 5 posters. • Show Examples • Project: Make a parachute for an Egg • Make it out of anything. • Paper / plastic bags, newspaper • String, tape, glue, staples • Empty cartons for basket • Project Rubric Next Week
Braking Distance • This equation is used when time is not involved (not given or asked for) • Vf^2 = Vi^2 + 2 * a * d • Notice: no time! • ______ is about to crash into _______. Their velocity is ________. If the cars are ______m apart, what acceleration do they need to have to avoid a crash?
What are our Equations? • Velocity = disp. / time • Vavg = Dd / Dt • Constant Velocity means no acceleration.. Use this forumla! • Standard unit for velocity is m/s • A = Vf – Vi / t • Df = ½a*t2 + Vi*t + di • Shortcut: t = sqrt(2*d/a) • Only to be used when falling and Vi = 0. • Vf^2 = Vi^2 + 2 * a * d • Acceleration due to gravity : g = -9.8 m/s2 • “fall, thrown, drop? Use g” CHAPTER 2 CHAPTER 3
9/29 Agenda • Collect Corrected Work • ACT/PSAE Practice • Distribute Problem Reading Trainer • Essential Questions: • What are the common elements to solving a physics problem?
Bellringer 10/1 • A ball rolls horizontally at 6 m/s. How long will it take the ball to cover 30 meters? • A ball rolls off of a table. It falls for 1 second before hitting the ground. How tall is the table? • Make a p-t graph of someone walking forward for 2 seconds, stopping for 2 sec, and backwards for 2 sec. • Extra credit: make a velocity-time graph of this too!
September 24 • A football is thrown down field. It is caught at the same height that it was thrown. It is thrown at 20 m/s. How fast is it going when it is caught? • Write in 1-3 complete sentences HOW DO YOU KNOW?!? • Bellringer • Interim Assessment #1 • Do not write on the test • You must bubble in Name and ID • You MUST WRITE at the top: “Hedden Period _” • Pass back work • Go over the toughest assignment Bellringer Agenda
Trigonometry • Used for Right triangles only • Involves Sine, Cosine, and Tangent • Can be used to find an angle or side of a triangle by using two other parts of the triangle. • Pythagorean Theorem a2 + b2 = c2 • SOH CAH TOA