# Physics: Principles and Problems. ACT/PSAE practice Intro to acceleration – What does it mean in common language? – What does it mean to a physicist?

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Physics: Principles and Problems

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!

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

 What does it mean to you in common conversation?  What is the book’s definition?  “Deceleration” is just acceleration in a negative direction

 ______ is riding their bike to school. They

 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?

When you fall, do you fall at a constant rate or accelerated rate? How do you know? Use complete sentences (UCS).

 Is acceleration a scalar or vector? How do you know? Use complete sentences (UCS).

 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?

 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?

 If your car can accelerate at 5 m/s 2, how long will it take the car to accelerate from 10 m/s to 25 m/s?

 Bellringer  Graphing Assignment  Acceleration WS 2 pushed back to Thursday (for this class only)

 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!

 Bellringer  Average Velocity WS corrections [10 min]  Reading Guide 3.1-3.2 [10 min]  Finish Acceleration ws 2

 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?

 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?

 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

 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?

CHAPTER 2CHAPTER 3  Velocity = disp. / time ◦ V avg =  d /  t ◦ Constant Velocity means no acceleration.. Use this forumla!  Standard unit for velocity is m/s  A = Vf – Vi / t  Df = ½a*t 2 + 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/s 2 ◦ “fall, thrown, drop? Use g”

 Collect Corrected Work  ACT/PSAE Practice  Distribute Problem Reading Trainer  Essential Questions:  What are the common elements to solving a physics problem?

 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!

BellringerAgenda  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

 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 a 2 + b 2 = c 2  SOH CAH TOA

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