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 Motion of an object  Average Speed  Velocity  Acceleration.

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Presentation on theme: " Motion of an object  Average Speed  Velocity  Acceleration."— Presentation transcript:

1  Motion of an object  Average Speed  Velocity  Acceleration

2  Objects move in relation to a reference point. Reference point The tree is the reference point since it stays in place.

3  When an object changes position over time relative to a reference point, the object is in motion.  When the motorcycle changes position over time relative to the tree, the motorcycle is in motion.

4  You can describe the direction of the object’s motion with the reference direction…  North, south, east, west, up, or down.

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6  The speed of an object is the distance traveled by an object divided by the time taken to travel that distance.  S = distance/time (S = d/t)

7  If the motorcycle traveled 10 meters and it took it 2 seconds, how fast is the motorcycle traveling?  S = d/t S = 10 meters/ 2 seconds  S = 5 m/s  Don’t forget units!

8  Think to yourself about how you walk class to class….is it at a constant pace?  Most often, objects do not travel at a constant speed, so we need to calculate the average speed.  Average speed = total distance/total time

9  Mr. Summers swims a distance from one end of a 50 m pool to the other end in a time of 25 s. What is Mr. Summer’s average speed?  S = d/t  S = 50 m/ 25 s  S = 2 m/s

10 Distance (m)Time (s) Create a graph of this data. Label your y-axis as “distance” and your x- axis as “time”.

11  Since the graph is comparing distance to time, then the line represents SPEED!  S = d/t Distance (m) Time (s) Speed of object

12  Picture two birds leaving a tree at the same time.  They both fly at 10 km/h for 5 min. Why don’ they end up at the same place?  They went in different directions!

13  The speed of an object in a particular direction is called velocity.  The speeds of the birds were the same, but they had different velocities.

14  Which is the correct way to describe the velocity of a car traveling on I-5?  “A car’s velocity is 60 m/h”  “A car’s velocity is 60 m/h south.”

15  Picture sitting in a car at a stop light, when it turns green what happens to the car?  “Speeding up” is commonly described by using the word acceleration.  However, in science it means much more…

16  Acceleration is the rate at which velocity changes over time…..  So velocity changes when speed changes, direction changes, or both.

17  A car accelerates when it increases it’s speed from 25 to 35 m/h.  A car accelerates when it turns a corner.  A car accelerates when it puts it’s brakes on for a stop sign.

18  Positive acceleration – increase in velocity.  Negative acceleration – decrease in velocity (also called deceleration)  List two examples of each in your compbook. Share with your neighbor.

19  Acceleration is also how fast velocity changes. … The faster the velocity changes, the faster the acceleration.

20  Since acceleration is the rate at which velocity changes over time…..  Acceleration = final velocity – starting velocity time it takes to change velocity  A = V f – V i t

21  Mrs. Rhoades is riding her bike south downhill. At the top of the hill she is going 1 m/s south and at the bottom she is going 5 m/s south. It took her 4 sec to go travel the entire hill. What was Mrs. Rhoades acceleration down the hill?  A = V f – V i t  A = 5 m/s – 1 m/s = 1 m/s/s South 4 s

22  A plane passes over point A at a velocity of 240 m/s north. 40 seconds later, it passes point B at a velocity of 260 m/s north. What is the plane's average acceleration?  A = V f – V i t  A = 260 m/s – 240 m/s = 0.5 m/s/s north 40 s

23 Create a graph of this data. Label your y-axis as “Velocity” and your x- axis as “time”. Velocity (m/s)Time (s)

24  Since the graph is comparing velocity to time, then the line represents acceleration!  A = V f – V i t Velocity (m/s) Time (s) Acceleration of object

25  Think about a person spinning around on their feet… are they accelerating?  Yes! An object traveling in a circular motion is always changing its direction, therefore always changing velocity. So its accelerating!

26  The acceleration that occurs in a circular motion is called centripetal acceleration!  Centripetal acceleration happens on a Ferris wheel or as the moon orbits the earth.


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