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Understanding Acceleration

Understanding Acceleration. Acceleration Calculating Acceleration. I. The Acceleration Equation. Acceleration – a measure of how quickly something speeds up , or slows down , or changes direction

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Understanding Acceleration

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  1. Understanding Acceleration Acceleration Calculating Acceleration

  2. I. The Acceleration Equation • Acceleration – a measure of how quickly something speeds up, or slows down, or changes direction • Positive Acceleration – means that the velocity is increasing in the forward direction (speeding up forward) • Negative Acceleration – means that the velocity is decreasing in the forward direction (slowing down forward) • What is involved in the acceleration equation? • My truck is really fast, it can go from 0mi/hr – 60mi/hr • What’s missing in the above statement? • The time it takes to go from 0mi/hr – 60mi/hr • Acceleration then must include how much you speed up or slow down and the time it takes • For example if it takes my truck 6s to speed up from 0 to 60mi/hr, it must be speeding up by 10mi/hr every second. • Its acceleration is:

  3. I. The Acceleration Equation • The Equation for acceleration is: • Mathematically, the equation is written as:

  4. Comprehension Check • What are the three ways that an object can accelerate? • Speed up; Slow down; Turn • Indicate whether each object below is accelerating or not. • Car turning a corner without slowing down or speeding up. • Accelerating (changing direction) • A basketball right after it is tossed into the air. • Accelerating (slowing down) • A car driving on a straight interstate with its cruise control on. • Not accelerating (not turning, speeding up, or slowing down) • A water balloon right after it is dropped from a balcony. • Accelerating (speeding up) • A kid sliding along the floor in his or her socks. • Accelerating (slowing down)

  5. Basketball Acceleration Post Lab Questions • What does the slope of distance versus time graph tell us? • The slope tells us the velocity (the speed and direction) of the object. • When the graph’s slope is curving, was the basketball accelerating or moving steadily? • Since the velocity changes when the graph curves the basketball is accelerating. • When the slope is straight, was the basketball accelerating or moving at a steady velocity? • A straight slope means constant velocity. The velocity from the tangent button barely changes at all.

  6. Basketball Acceleration Post Lab Questions -Slope decrease from a large positive slope to zero -Slowing down forward -Slope increases from zero to a large negative slope -Speeding up backwards -Constant positive slope -Constant forward velocity III IV -Constant negative slope -Constant backward velocity -Slope decrease from a large negative slope to zero -Slowing down backward -Slope increases from zero to a large positive slope -Speeding up forward V II I VI

  7. Basketball Acceleration Post Lab Questions • Using the Tangent data and the video, what was happening to the velocity of the ball when it was touching the hands of the thrower? • The ball was either speeding up or slowing down. That is it was accelerating. • What was happening to the ball when it was not touching the hands of the throwers? • The slope and velocity was constant when it was flying through the air. • Looking at the screen what happens to the spacing of the dots at high velocity compared to small velocities? • The dots are closer together when the ball is moving slowly because the ball is covering less distance every frame.

  8. Sketch a graph for each of the following scenarios.

  9. Comprehension Check • Identify each of the following objects as either accelerating or not accelerating • Mike is jogging down the street at 3m/s • No acceleration – straight line and constant speed • Joe is applying the brakes as rides his bike • Negative acceleration • Sarah jogs around the track at a constant speed • Acceleration, changing direction • Michelle sits down and then sprints to catch up • Positive Acceleration – speed is increasing • The earth orbits the sun • Acceleration – changing direction

  10. II. Example Problem 1 • A Dodge Viper can go from 0mi/hr to 60mi/hr in 3.5s. What is the acceleration of the car? ΔV = Δt = a = 60mi/hr 2.7s ? This means that the velocity of the car is increasing by 17.1 mi/hr every second.

  11. III. Example Problem 2 • Sharon, a skydiver, can reach velocities of 55.0m/s while in freefall, which means she is traveling the length of a football field in 2s. Once she deploys her parachute, it takes her 2.7s to slow down to her landing velocity of 3.2m/s. What is Sharon’s acceleration? ΔV = Δt = a = 3.2m/s – 55.0m/s= -51.8m/s 2.7s ? The negative sign indicates that the velocity is decreasing at a rate of 19.2m/s every second.

  12. IV. Solving for ΔV • In a vacuum, all objects near the Earth’s surface accelerate at 9.81m/s/s. If a water balloon is dropped from a balcony and falls for 2.9s, what was its change in velocity? ΔV= Δt= a= ? 2.9s -9.81m/s2

  13. V. Solving for ∆t • How long does it take the shuttle to slow down from 28,200km/hr to its landing velocity of 352km/hr if it’s acceleration is -879km/hr/min? ΔV= Δt= a= 28,200km/hr - 352km/hr = 27,848km/hr ? -879km/hr/min

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