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Matter in Motion

Matter in Motion. Measuring Motion. Motion. Reference point is the object that appears to stay in place. Examples: Earth’s surface, trees, building. Motion is an object’s change in position relative to a reference point.

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Matter in Motion

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  1. Matter in Motion Measuring Motion

  2. Motion Reference point is the object that appears to stay in place. Examples: Earth’s surface, trees, building. Motion is an object’s change in position relative to a reference point. The direction of the object’s motion is described with a reference direction, “north, south, east, west, up, down, …”.

  3. Speed • Speed is the distance traveled by an object in a given amount of time. Speed = distance time • SI unit for speed is meters per second (m/s). Other common unit is Km/h. • Most objects do not move at constant speeds for very long. • Average speed is calculated using the following equation: Average speed = Total distance Total time

  4. Recognizing speed on a graph If something is not moving:

  5. Problems on calculating average speed Answer: Average speed = Total distance Total time Average speed = 50 m 25 s = 2 m/s Problem 1: What is the average speed of an athlete who swims a 50 m pool in a time of 25 seconds?

  6. Problems on calculating average speed Answer: Average speed = Total distance Total time Distance = Speed  time Distance = 100 km/hr  6 hr = 600 Km Problem 2: If you drive at 100 km/hr for 6 hours, how far will you go?

  7. Problems on calculating average speed Answer: Average speed = Total distance Total time Distance = Speed  time Distance = 12 m/s  (1560) s = 12  900 = 10800 m = 10.8 Km Problem 3: If you run at 12 m/s for 15 minutes, how far will you go?

  8. Problems on calculating average speed Answer: Average speed = Total distance Total time Time = Total distance Speed Time = 1000 m = 1.18 seconds 850 m/s Problem 4: A bullet travels at 850 m/s. How long will it take a bullet to go 1 km?

  9. This graph shows several stages of motion: • Stage 1: 100 m in 10 s • Stage 2: 50 m in 10 s • Stage 3: 150 m in 20 s • 1) Calculate the speed as indicated by each of the colors. • 2) What is the total distance? • 3) Calculate the average speed.

  10. Solution Stage 1: S= d/ t 100 m/10 s= 10 m/s Stage 2: S= d/t 50 m/10 s= 5 m/s Stage 3: S= d/t 150 m/20 s= 7.5 m/s Avg. Speed= T. d/ T. t 300 m/40 s= 7.5 m/s Distance = 300 meters

  11. Velocity is the speed of an object in a particular direction. Velocity can be changed if either its speed or direction changes. Combining velocities:  When two velocities are in the same directions, add them together to find the resultant velocity.  When two velocities are in opposite directions, subtract the smaller velocity from the larger velocity to find the resultant velocity.

  12. Acceleration Is the rate at which velocity changes over time. An object accelerates if its speed, its direction or both change.  An increase in velocity causes positive acceleration.  A decrease in velocity causes negative acceleration or deceleration.

  13. Decide whether or not acceleration occurs in the followings: Riding at 9 Km/h. After 10 min. 6 Km/h. Riding at a constant speed of 11 Km/h around the building. Riding in a straight line at a constant speed of 10 Km/h.

  14. Calculating average acceleration: • Average acceleration = Final velocity – starting velocity time it takes to change velocity • Unit for acceleration is meters per second (m/s)/s (m/s2).

  15. Circular motion: Acceleration that occurs in circular motion is known as centripetal acceleration.

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