2. Physics Unit 2 1-D and 2-D Motion

3. Topics: 4 What is Linear Motion? 4 Vector vs. Scalar Quantities 4 Distance vs. Displacement (Comparison) 4 Speed vs. Velocity (Comparison) 4 Velocity: Constant, Average, Instantaneous 4 Acceleration

4. Linear Motion 4 Motion in one direction 4 Example: the motion of a Marta train- the train moves either forward or backward along the track

5. SCALAR PHYSICAL QUANTITY Can be completely specified by its magnitude with appropriate units. It has no direction. Ex) Distance, time, speed, mass, etc.

6. PHYSICAL QUANTITY VECTOR Has a magnitude, a unit and a direction e.g displacement, velocity, acceleration, force.

7. Demonstrating a Vector The direction of the arrow indicates the direction of the vector quantity. The length of the arrow indicates the magnitude of the vector quantity. A Tail Head

8. ADDING VECTORS -ONE DIMENSIONAL 4 Vectors are added by placing the tail of one vector at the head of the other vector. 4 A third vector (C) is drawn by placing the tail of one vector at the head of the other. AB C

9. EXAMPLES 200m100 m 300 m-resultant 50 m 30 m 20 m-resultant

10. Distance How far an object actually moves

11. Displacement Displacement does not always equal distance traveled Displacement can be positive or negative

12. Displacement

13. Displacement is ZERO

14. Distance vs. Displacement 4 Displacement- a change in position  d = d f - d i final position - initial position

15. Displacement Questions 1. Amy runs 2 blocks south, then turns around and runs 3 miles north. 2. Jermaine runs exactly 2 laps around a 400 meter track. 3. Ray runs 30 feet north, 30 feet west, and then 30 feet south. 4. Jamison turns around 5 times. 5. David walks 3 km north, then turns and walks 4 km east.

16. Speed and Velocity

17. Speed 4 Speed is a rate 4 Speed is a rate of the distance traveled in a unit of time

18. Speed 4 Speed is a measure of how fast something is moving 4 Speed is a SCALAR quantity- it only requires a magnitude

19. Calculating Speed Speed = Distance traveled Time

20. What is the fastest land animal? 4 The cheetah can travel at speeds up to 100 km/h!!

22. Velocity 4 The terms speed and velocity are used interchangeably 4 Velocity is speed in a given direction

23. Velocity 4 VECTOR quantity- it must have both magnitude and direction –magnitude is a number –direction: north, south, east, west, etc.

24. Units of Speed and Velocity 4 Units of distance /unit of time 4 Meters/sec, miles/hour, kilometers/hour, nanometers/sec,

25. Velocity Graphs (position vs. time) A B A C B D

26. Constant velocity 4 Occurs when the average velocity is the same for all time intervals 4 Also called uniform velocity

28. Constant Velocity Graph 4 The velocity is equal to the slope of a distance versus time graph

29. Average Velocity 4 Used to describe an objects motion when the velocity is changing, i.e. speed up, slow down, stop, start, etc. 4 Average velocity will equal the magnitude of an object moving with a constant velocity.

30. Calculating Average Velocity 4 Total distance (displacement)/total time 4 slope of line drawn from start to stopping point on a distance time graph.

31. Average Velocity 4 DISPLACEMENT divided by TIME v avg = average velocity = change in position = displacement change in time time interval

33. Instantaneous Velocity 4 The velocity of an object AT a particular INSTANCE or moment.

34. Instantaneous Velocity 4 Determined by drawing a tangent line to the curve and determining the slope of the line.

35. Example 4 During her first track meet, Andrea runs with an average velocity of 6.02 m/s to the east. What distance does Andrea cover in 137 s? Given: v = 6.02 m/s t = 137 s d = ? V=

36. Example 4 Last weekend I traveled from Lawrenceville to Dillard (100 km). If I drove 50 km/h for the first 50 km and 100 km/h for the second 50 km, what was my average velocity?

37. Acceleration Acceleration is the rate of change in velocity

38. Acceleration Acceleration is shown by a curved graph when position (distance) versus time is plotted.