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## Unit 4 Class Notes

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**Days 1 thru 3**Projectile Motion Unit 4 Class Notes Accelerated Physics**Day #1**Free-Falling Object Review**Day #2**Horizontal Projectiles**Horizontal Projectiles**• The first example on the previous slide is often called a horizontal projectile. This is the first example we will look at. • The object is given an initial horizontal velocity. Thus, velocity is purely horizontal (no y component) • Our initial velocity in the y direction viy=0. • Next, analyze the motion in the horizontal and vertical direction separately.**Figure #3**Figure #2 Figure #1 From Reading Assignment handout**Using figures from previous slide**• Figure 1 – Free fall object. The object’s position after every second of falling is shown. The object is accelerating because it travels a longer distance in each successive time interval. • Figure 2 – Horizontally traveling object at a constant velocity. Acceleration equals zero so each time interval shows the same distance traveled. • Figure 3 – A combination of both these motions. When a projectile falls, it accelerates downward so its y direction matches figure 1. However, since nothing (including air) slows the object down as it moves horizontally, its x direction matches figure 2.**Since projectile motion is a combination…**• We will analyze the motion separately. The only shared variable between the two motions is TIME (since they both occur in the same amount of time) • Solve for time in vertical (y) side, then plug in to horizontal side.**There are so few equations in the x direction because a=0 so**velocity is constant. • In the y direction we have the 4 familiar acceleration formulas. • EXAMPLE 1: A ball is rolled off a flat roof hat is 30 m above the ground. If the ball’s initial speed is 15 m/s, find the time needed to strike the ground as well as the distance that it lands away from the building. Horizontal (x) Vertical (y) From Reading Assignment handout**Horizontal (x) Vertical (y)**From Reading Assignment handout**Horizontal (x) Vertical (y)**From Reading Assignment handout**Day #3**COMPETITION LAB!!!! (Ball Rolling Off Table)**Day #4**Tracking and Impact Velocity**Side-ways Toss (Gravity Turned Off)**Each position corresponds to 1 sec later than the previous position (starting with the red dot)**Side-ways Toss (Gravity Turned Off)**Horizontal Projectiles Free-Fall**Impact Velocity**Side-ways Toss (Gravity Turned Off) Horizontal Projectile Free-Fall Velocities**Impact Velocity**Vfx q Vfy Vimpact**Horizontal (x)**Vertical (y) 4 m/s 19.6 m/s V2 V2 = 20 m/s [78.46o BH] From Reading Assignment handout**Day #5**Angled Projectiles on Flat Ground**What we’ve done so far**What we still need to do**Side-ways Toss (Gravity Turned Off)**Throw-up, then Free-Fall Projectiles at Angles**So, what are the Equations we use for this “NEW” type of**projectile???? Horizontal Vertical There are NO NEW EQUATIONS **vi**viy q vix vi So…..How are “angled” projectiles different than “horizontal” projectiles? q Viy = 0 (for horizontal projectiles) = visinq Viy = something, + or - (for horizontal projectiles) = vicosq**q**Vix = Vfx = Vx = 0 (since ax = 0) Vy, top = 0 When rising, Vy is positive (when falling = Vy is negative) The velocity at every moment in time is the resultant of the two velocity components If launching and landing occurs at the same height (on level ground) then the launching/landing speeds & angles are the same What are some important things to remember? vi q**Day #6**MORE Angled Projectiles … Sometimes NOT on Flat Ground