ACCELERATION What is acceleration Probably heard it mean

ACCELERATION

• What is acceleration? – – Probably heard it mean: “the process of speeding up” More specifically: the rate at which velocity changes. • Remember that velocity involves a change in either speed or direction.

• Therefore, acceleration refers to increasing speed, decreasing speed, or changing direction. – Increasing speed • – Decreasing speed • – What is a real world example of increasing speed? What is a real world example of decreasing speed? Changing Direction • So if a car has the same speed, if it goes around a curve it is accelerating (change in direction).

• Try this on your own: – If a car can go from 0 to 60 meters per second in 5 seconds, what is the car’s acceleration? • • – Final speed=60 meters/second Initial speed =0 mph meters/second Time =5 mph Therefore acceleration is (60 meters/second - 0 meters/second)/ 5 secs= 12. What is the unit on this number • • (Meters/second)/second= Meters/(second 2) =m/s 2

• • SI unit of acceleration is m/s 2 Try these problems by yourselves: – A roller coaster starts at 4 m/s. Three seconds later its speed is 22 m/s. What is the average acceleration? • – (22 -4)/3 = 6 m/s 2 If the roller coaster continues its current acceleration how fast will it be traveling in 3 seconds? • • • Currently going 22 m/s. One second later it would increase by 6 m/s, going 28 m/s. So for each second it increases by 6 m/s. Therefore, after 3 seconds it will have increased by 18 (6*3), going 40 m/s (18+22).

• How do we calculate acceleration? – – To determine acceleration, you must calculate the change in speed per unit of time. So acceleration= Final speed – Initial speed Time

• When you have a graph (speed versus time), how is acceleration related to the line’s slope? – The slope= acceleration of an object.

GRAPHING ACCELERATED MOTION, CONTINUED • Acceleration can also be seen on a distance vs. time graph. – The distance vs. time graph is not a straight line when the velocity is not constant. – This curved line indicates that the object is under acceleration.