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Jennifer Brown Section 4.3 http://vimeo.com/609333 EXAMPLE: Kingda Ka Coaster: 0 – 128 mph in 3.5 seconds through hydraulic system & compressed air. Jennifer Brown Sections 4.1 - 4.3 Acceleration – •The rate at which your speed (or velocity) changes. •If your speed increases by 1 meter per second for each second, then your acceleration is 1 meter per second per second (m/s2). Jennifer Brown Sections 4.1 - 4.3 Jennifer Brown Sections 4.1 - 4.3 Can you have acceleration if you are travelling at constant speed? • No: There is zero acceleration at constant speed because the speed does not change. Jennifer Brown Sections 4.1 - 4.3 Speed and acceleration are not the same thing. You can be moving (constant speed), but have no acceleration (think cruise control). Jennifer Brown Sections 4.1 - 4.3 Acceleration describes how quickly speed changes. Acceleration is the change in speed divided by the change in time. Jennifer Brown Sections 4.1 - 4.3 Jennifer Brown Sections 4.1 - 4.3 An acceleration of 20 km/h/s means that the speed increases by 20 km/h each second. The units for time in acceleration are often expressed as “seconds squared” and written as s2. Jennifer Brown Sections 4.1 - 4.3 The word “acceleration” is used for any change in speed, up or down. Acceleration can be positive or negative, which makes it a what? •VECTOR! Jennifer Brown Sections 4.1 - 4.3 Positive acceleration adds more speed each second. Things get faster. Speed increases over time. Jennifer Brown Sections 4.1 - 4.3 Negative acceleration subtracts some speed each second. Things get slower. People sometimes use the word deceleration to describe slowing down. Jennifer Brown Sections 4.1 - 4.3 How do we solve problems dealing with acceleration? : 1) Calculate the acceleration of an airplane that starts at rest and reaches a speed of 45 m/s in 9 seconds? • Answer: 5 m/s2 2) Calculate the acceleration of a car that slows from 50 m/s to 30 m/s in 10 seconds? • Answer: -2 m/s2