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Slide 2 Slide 3 Acceleration Acceleration = speeding up Acceleration the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction Slide 4 Types of acceleration Increasing speed Example: Car speeds up at green light Decreasing speed Example: Car slows down at stop light Changing Direction Example: Car takes turn (can be at constant speed) screeeeech Slide 5 Question How can a car be accelerating if its speed is a constant 65 km/h? If it is changing directions it is accelerating Slide 6 Calculating Acceleration If an object is moving in a straight line Units of acceleration: Distance/ time = distance/time 2 time m/s 2 Slide 7 Calculating Acceleration 0 s 1 s2 s3 s4 s 0 m/s 4 m/s 8 m/s 12 m/s16 m/s Slide 8 Question A skydiver accelerates from 20 m/s to 40 m/s in 2 seconds. What is the skydivers average acceleration? Slide 9 Graphing Acceleration Can use 2 kinds of graphs Speed vs. time Position vs. time Slide 10 Graphing Acceleration: Speed vs. Time Graphs 1)Speed is increasing with time = accelerating 2)Line is straight = acceleration is constant Slide 11 Graphing Acceleration: Speed vs. Time Graphs 1)In Speed vs. Time graphs: Acceleration = Rise/Run = 4 m/s 2 s = 2 m/s 2 Run = 2 s Rise = 4 m/s Slide 12 Graphing Acceleration: Position vs. Time Graphs 1)On Position vs. Time graphs a curved line means the object is accelerating. 2)Curved line also means your speed is increasing. Remember slope = speed. Slide 13 Question Above is a graph showing the speed of a car over time. 1) How is the speed of the car changing (speeding up, Slowing down, or staying the same)? 2) What is this cars acceleration? 1)The car is slowing down 2)Acceleration = rise/run = -6m/s 3s = -2 m/s 2 Run = 3 s Rise = -6 m/s Slide 14 Question: 1)Which line represents an object that is accelerating? The black and red lines represent a objects that are accelerating. Black is going a greater distance each second, so it must be speeding up. Red is going less each second, so must be slowing down Remember: in position vs. time graphs: curved line = accelerating, straight line = constant speed Slide 15 Question: Hard one Slide 16 Free fall The constant acceleration of an object moving only under the force of gravity If there was no air, all objects would fall at the same speed regardless of the masses Slide 17 Acceleration due to gravitational force d = v i t + gt 2 If v i = 0, then d = gt 2 g = acceleration due to the force of gravity = 9.8 m/s 2 = 10 m/s 2 Slide 18 Free fall After 1 second falling: v= 10 m/s After 2 seconds: v = 20 m/s After 3 seconds: v = 30 m/s Slide 19 Falling Air resistance will increase as it falls faster An upward force on the object Eventually gravity will balance with air resistance Reaches terminal velocity - highest speed reached by a falling object. Slide 20 Bozeman videos http://www.bozemanscience.com/pos ition-vs-time-graph-part-2 http://www.bozemanscience.com/spe ed-velocity-acceleration Slide 21 Questions Answer the following questions and email me your answers. (seibert- [email protected] )seibert- [email protected] 1. How can a car accelerate without the speedometer changing? 2. What does the slope of a velocity vs time graph give you? 3. What is the value of the acceleration due to the force of gravity on Earth? 4. What is the color of the object that is rolled across the table by Mr. Andersen?

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