1 / 19

Chapter 2

Chapter 2. Representing Motion. Motion diagram- a series of images that show the position of an object at specific time intervals. Particle model- a simplified version of the motion diagram in which the images are replaced by single points.

misu
Download Presentation

Chapter 2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 2 Representing Motion

  2. Motion diagram- a series of images that show the position of an object at specific time intervals

  3. Particle model- a simplified version of the motion diagram in which the images are replaced by single points.

  4. When representing motion 2 types of quantities will be used: • Scalars- Quantities that describe only size or magnitude, they are just numbers without a specific direction. Examples would be distance 87 km, 23 m, 400 ft • Vectors- Quantities that describe both magnitude and direction; examples 87 km east, 23m WSW, 400 ft south • Vectorsare represented by arrows that are drawn to scale; When doing a problem involving vectors choose a scale that will produce reasonable vectors (5-10 cm)

  5. 80 m/s NE 120 m/s SE 66 m/s W N 8 cm 6.6 cm W E 12 cm Scale 1 cm = 10 m S

  6. Resultant vectors-the some of 2 or more vectors • A boy travels .5 km E to a store to pick up bread and milk. The boy continues .2 km E to deliver the milk and bread to his grandmother. What’s the scale? 1cm=.1km 5 cm 2 cm How far did the boy travel? .7 km 7 cm

  7. Time intervals and displacements • Two things are used to analyze motion. • Time Intervals- the difference between 2 times Δt= tf - ti Time Interval = final time - initial time • Displacement- the change in position of an object Δd= df – di Displacement = final position minus initial position

  8. Distance vs. Displacement • Distance and displacement are not necessarily the same thing. • Distance - How far you travel regardless of direction. • Displacement -"Change in position” this not only takes into account distance but direction as well

  9. Example Suppose a person moves in a straight line from the lockers (at a position di = 1.0 m) toward the physics lab (at position = 9.0 m) , as shown below 1.0 m 9.0 m Δd= df – di = 9.0m – 1.0m = 8.0m

  10. In this example the distance would be described as 8.0 m, but the displacement would be described as 8.0 m to the right Suppose the person turns around! Δd= df – di = 1.0m – 9.0m = -8.0m The answer is negative so the person must have been traveling horizontally to the left

  11. What is the DISPLACEMENT for the entire trip? 0 m is the displacement because you have ended at the same spot What is the total DISTANCE for the entire trip? The distance traveled is 16m 8m + 8m= 16m

  12. Position-Time Graphs • Graph used to show the position of an object at a specific time. • Y axis- displacement or position • X-axis- time

  13. Where is the object located at 3s? At what point is the object at 7m? What is happening to the object between 6-11s ? What is happening between 11-17s ?

  14. Velocity- the speed of an object in a specific direction; it is a vector quantity because it describes magnitude (how fast) and direction • Speed- is simply how fast something is moving; It is a scalar quantity because there is no direction associated with it

  15. Average Velocity Velocity is defined as: “The RATE at which DISPLACEMENT changes”. d d d If you are given a Displacement vs. Time graph, to find the velocity of an object during specific time intervals simply find the slope.

  16. Slope Because velocity is a vector quantity the direction is usually described as being in a positive or negative (backwards) direction d d d

  17. What is the average velocity of the object between 6-11s? 0 m/s object is stopped What is the average velocity of the object between 15-17s? -1.5 m/s in a negative direction What is the average velocity of the object between 0-6s? 1.7 m/s in a positive direction

  18. Average Speed - the average speed of an object does not indicate direction therefore is equal to the absolute value of average velocity Instantaneous velocity – the speed and direction of an object at a specific time. Instantaneous speed – the speed of an object at a specific time

  19. Equations are often more useful than displacement-time graphs; If an object is moving at a constant velocity its graph will be a straight line. y=mx + b d= vt + di dposition/displacement of object v average velocity t time di initial position

More Related