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Published byDandre Goss Modified about 1 year ago

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Acceleration (a)– the rate of change of velocity (can be +, -, or centripetal) Deceleration– only negative acceleration (slowing down) Centripetal Acceleration– acceleration that occurs when changing direction (turning) Freefall– objects falling due to gravity Force is what you feel when you accelerate

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Since acceleration is a change in velocity and velocity has 2 parts We can accelerate by Changes in speed 1. Speed up (+ acceleration) 2. Slow down (- acceleration) Changing Direction 3. Turning Changing both speed and direction

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We don’t see acceleration of an object well with our eyes But if we look at a speedometer we can see speed change. Acceleration is a picture of what your speedometer is doing

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SLOW ACCELERATIONFAST(ER) ACCELERATION

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THE VARIABLESTHE GRAPH Speed ( or velocity)is the dependent variable Time is the independent variable Time Speed Graph setup = Formula a=a= sp tt

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Acceleration( sp/ t)= slope on an acceleration graph (rise/run) Acceleration Graph Time Speed + acceleration (gas pedal) Constant Speed (0 acceleration) (cruise control) - Acceleration (deceleration) (brake pedal) No motion - stopped

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Positive (+) slope = + accel (speeding up) Negative (-) slope = - accel (slowing down) Zero (0) slope (flat line) = 0 accel (constant speed) speed t t t

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Steeper slopes show greater acceleration Straight lines = Constant acceleration Steady increase or decrease in speed speed t t Accelerates quickly Accelerates slowly decelerates slowly decelerates quickly When is the speed = to 0 (stopped)?

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Describe which sport you think this graph represents and why. Golf Skydiving Fishing 100-meter dash Drag racing Speed Time

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Rise–change in the graph on the vertical axis (Speed) Run–change in the graph on the horizontal axis (Time) Acceleration= sp 2 -sp 1 t 2 -t 1 Slope = = Y 2 -y 1 X 2 -x 1 rise run P1 (0 s, 0 km/h) t 1 sp 1 P2 (20 s, 20 km/h) t 2 sp 2 P1P2 a=a= sp 2 -sp 1 t2-t1t2-t1 = 20 km/h 20 s = = 1 km/h/s 20 km/h - 0 km/h 20 s – 0 s

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What is the acceleration of the object from 0 – 20 s? What is the speed of the object from 20 – 40 s? What is the speed of the object from 40 – 60 s? Acceleration(slope) = sp 2 – sp 1 (rise) t 2 – t 1 (run) = (20–0 m/s) ( 20 – 0 s) = 20 m/s 20 s = 1 m/s/s Acceleration(slope) = sp 2 – sp 1 (rise) t 2 – t 1 (run) = (20–20 m/s) ( 40 – 20 s) = 0 m/s 20 s = 0 m/s/s Acceleration(slope) = sp 2 – sp 1 (rise) t 2 – t 1 (run) = (0–20 m/s) ( 60 – 40 s) = -20 m/s 20 s = -1 m/s/s

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Acceleration= final speed – initial speed final time – intial time m/s, cm/min, km/h s, min, hr m/s/s, cm/min/min, km/h/s Since: sp 2 = final speed, sp 1 = initial speed t 2 = final time, t 1 = initial time a = (sp f – sp i ) (t f – t i ) a = (sp 2 – sp 1) (t 2 – t 1 )

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Acceleration= final speed – start speed final time – start time or x a tt sp ÷ sp = sp 2 – sp 1 t = t 2 – t 1 sp2=final speed, sp1=start speed t2=final time, t1=start time Since: Then: a = sp t

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or x a tt sp ÷ A kid is sledding down a hill. When he enters the course his speed is 10 m/s. After 2 seconds he has reached a speed of 26 m/s. What was his acceleration? GivenFormulaSetupSolution List Given Info And Unknown: sp 1 = 10 m/s sp 2 = 26 m/s t = 2 s a= ? Show Needed Equations: a = Substitute with Units & Show Math: a = Circles Answer with Units: a = a = 8 m/s/s (sp 2 – sp 1 ) tt 26 m/s-10 m/s 2 s 16 m/s 2 s

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Freefall: Objects falling due to gravity All objects accelerate at the same rate due to gravity during freefall regardless of their mass Objects may reach terminal velocity sooner due to air resistance Gravitational acceleration (g) = 9.8 m/s/s on earth

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or x a tt sp ÷ A woman jumps from a plane. She opens her parachute five seconds later. How fast was she going when she opened her shoot (disregard air resistance)? GivenFormulaSetupSolution List Given Info And Unknown: sp = ?? t = 5 s a= g=9.8 m/s/s Show Needed Equations: sp = Substitute with Units & Show Math: sp = Circles Answer with Units: sp = 49.2 m/s a · t 9.8 m/s/s· 5 s

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