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11.3 Acceleration What Is Acceleration? Changes in Speed 11.3 Acceleration What Is Acceleration? Free fall 11.3 Acceleration What Is Acceleration? Each second an object is in free fall, its velocity increases downward by 9.8 meters per second. The change in the stone’s speed is 9.8 m/s2, the acceleration due to gravity. t=0s v = 0 m/s t=1s v= t=2s v= t=3s v= 11.3 Acceleration What Is Acceleration? Changes in Direction 11.3 Acceleration What Is Acceleration? Constant Acceleration 11.3 Acceleration Calculating Acceleration Acceleration is the rate at which velocity changes. Vi is the initial velocity, vf is the final velocity, and t is total time. 11.3 Acceleration Calculating Acceleration Calculating Acceleration A ball rolls down a ramp, starting from rest. After 2 seconds, its velocity is 6 meters per second. What is the acceleration of the ball? 11.3 Acceleration Balancing Equations Read and Understand What information are you given? 11.3 Acceleration Balancing Equations Plan and Solve What unknown are you trying to calculate? What formula contains the given quantities and the unknown? 11.3 Acceleration Balancing Equations Plan and Solve Replace each variable with its known value. 11.3 Acceleration Balancing Equations Look Back and Check Is your answer reasonable? Objects in free fall accelerate at a rate of 9.8 m/s2. The ramp is not very steep. An acceleration of 3 m/s2 seems reasonable. 11.3 Acceleration Describing Ionic Compounds 1. A car traveling at 10 m/s starts to decelerate steadily. It comes to a complete stop in 20 seconds. What is its acceleration? 11.3 Acceleration Graphs of Accelerated Motion How does a speed-time graph indicate acceleration? 11.3 Acceleration Graphs of Accelerated Motion The skier’s acceleration is positive. The acceleration is 4 m/s2. 11.3 Acceleration Graphs of Accelerated Motion The biker moves at a constant speed and then slows to a stop. 11.3 Acceleration Graphs of Accelerated Motion A distance-time graph of accelerated motion is a curve. The data in this graph are for a ball dropped from rest toward the ground. An increasing slope means that the speed is increasing. 11.3 Acceleration Instantaneous Acceleration 11.3 Acceleration Assessment Questions 1. What is acceleration? a. b. c. d. the rate at which speed increases the time an object’s velocity increases the rate at which displacement changes the rate at which velocity changes 11.3 Acceleration Assessment Questions 2. A sports car can accelerate from 0 m/s to 28 m/s in four seconds. What is the acceleration of the car? a. b. c. d. 24 s 7 m/s 27 m/s 27 m/s 11.3 Acceleration Assessment Questions 3. If you were to sketch a displacement-time graph and a speed-time graph for an object experiencing constant acceleration, what would they look like? a. Both graphs would be linear, with the displacement-time graph being steeper. b. Both graphs would be linear, with the speed-time graph being steeper. c. Both graphs would be nonlinear. d. The speed-time graph would be linear; the displacement-time graph would be nonlinear. 11.3 Acceleration Assessment Questions 4. Which of the following is an example of negative acceleration? a. Mike starts riding his bike and uses the pedals to go from 0 km/h to 20 km/h. b. Mike pedals up a hill and gradually slows from 20 km/h to 5 km/h. c. Mike sits on his bike at the top of the hill and rests. d. Mike coasts downhill without pedalling, going from 0 km/h to 15 km/h. 11.3 Acceleration Assessment Questions 5. The acceleration at a specific point on a distancetime graph is the a. b. c. d. instantaneous acceleration. momentary acceleration. positive acceleration. numerical acceleration. 11.3 Acceleration Assessment Questions 6. If an object experiences a steady velocity change in a straight line, it is undergoing constant acceleration. True False