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Kawameeh 8 th Grade Science

Kawameeh 8 th Grade Science. Chapter 1 – Lesson 1. How do you know when something is moving?. Reference Point - . The starting point you chose to describe the location, or position of an object. An object’s distance and direction from a reference point. . Position - .

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Kawameeh 8 th Grade Science

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  1. Kawameeh 8th Grade Science

  2. Chapter 1 – Lesson 1

  3. How do you know when something is moving? • Reference Point - The starting point you chose to describe the location, or position of an object. An object’s distance and direction from a reference point. • Position - • A complete description of your position includes: A distance A direction A reference points

  4. A flagpole can be used as a reference point for finding a bicycle at a school.

  5. Practice Test Question

  6. Practice Test Answer

  7. Practice Test Question

  8. Practice Test Answer

  9. Measuring: Indicate which reference point is further. Use a ruler. (page 10)

  10. How does the description of an object’s position depend on a reference point? • An object’s position is its in a certain from a reference point. distance direction • Suppose your reference point changes… The description of the position will because the reference point is different, however the actual position change at all. change will not

  11. Reference Direction • Sometimes the terms and are used to determine reference direction. negative positive

  12. Describing the Reference Direction • A plus sign ( + ) indicates movement in the direction of the reference point. • A minus sign ( - ) indicates movement in the direction opposite of the reference point.

  13. If the reference direction is EAST • Anything moving in the direction toward the EAST would be • Anything moving in the opposite direction would be POSITIVE NEGATIVE

  14. Position as a Vector • A vector is a quantity in which two things must be specified: • 1. Distance from the reference point • 2. Direction from the reference point

  15. Dimensions and Reference Points • A dimension is when distance or length is measured in direction. one • If you were to describe a position in two directions you would be using two dimensions

  16. How would you describe your position? • Reference Directions in two dimensions: • North • Backward • South • East • Left • West • Up • Forward • Right • Down

  17. Changes in position due to motion • Motion - the process of changing position. How can you tell the boat moved? What if the fishing pole was the reference point? What if the buoy was a reference point?

  18. Distance vs Displacement • Distance - • the amount of space between two objects. The total length of the actual path from start to end. • Displacement - the difference between the initial (first) position and the final position of an object. (straight line) • When would distance and displacement be the same? • When an object moves in a straight line in one direction.

  19. Displacement • Direction of displacement is the direction from start point to end point • Size of displacement is the distance from the starting point to the ending point.

  20. Distance and Displacement

  21. Chapter 1 – Lesson 2

  22. Speed, Velocity and Acceleration • Speed, velocity and acceleration describe how an objects position and motion change through time. • Rates measure change in something over a length of time.

  23. What is speed? • A measure of the distance an object travels per unit of time. • Speed - • How could we increase an objects speed? • Move ~3 seconds for a distance of ~3meters • Move ~3 seconds for a distance of ~7meters • Move ~5 meters in ~5 seconds • Move ~5 meters in ~2 seconds

  24. Increasing an object’s speed • By increasing the distance the object travels in the same time. • Or • By decreasing the time it takes for an object to travel the same distance.

  25. Calculating Speed Speed (S) = distance object travels time it takes to travel distance S= d t

  26. Calculating Speed • If you know any two of the variables, you can calculate the missing variable.

  27. STEPS TO COMPLETING A FORMULA STEP 1 Write the formula Plug in the information that you are given STEP 2 Solve the answer STEP 3 STEP 4 Add your units STEP 5 Add your direction

  28. PRACTICE Calculate the speed of a car going 80 meters in 20 seconds.

  29. PRACTICE A girl runs 25 meters in 10 seconds. What is her speed?

  30. Constant Speed The rate of change of position in which the same distance is traveled each second.

  31. What distance has the car traveled at 2s? • How long will it take the car to travel 132m?

  32. Average Speed Average speed = total distance total time traveled S= td tt

  33. Solve the average speed: Melissa shot a model rocket 360 m into the air. It took the rocket 4s to fly that far. What was the average speed of the rocket?

  34. If Jessica ran 5 meters the first second, eight meters the next second, and 8 meters the third second to her house. What was her average speed?

  35. Instantaneous Speed Speed at a specific instant in time. When driving in a car you often change speed. What object in the car tells you your instantaneous speed? Speedometer

  36. Velocity • The speed and direction of a moving object. How is velocity represented? SPEED • The length of the arrow indicates the objects A LONGER ARROW • A greater speed is shown by THE OBJECTS MOTION • The arrow should point in the direction of

  37. Is their velocity the same? NO – they are both walking the same speed because the arrow’s are the same length, however their direction is different therefore the velocity is NOT the same

  38. In what ways can your velocity change? When speed of an object changes 2. When direction that the object moves changes 3. When BOTH the speed and direction change

  39. Chapter 1 – Lesson 3 • A measure of the change • in velocity during a • period of time.

  40. Acceleration 3. Change in direction (EVEN IF AN OBJECT IS TRAVELING AT A CONSTANT SPEED) • An object accelerates when its velocity changes as a result of: • 1. Increasing speed • 2. Decreasing speed

  41. Are the horses in the carousel accelerating even though their speed is constant?

  42. Calculating Acceleration

  43. A bicyclist started from rest along a straight path. After 5s, his speed was 8m/s. What was his acceleration during the time?

  44. Speed – Time Graphs • Shows how changes over time • X axis = • Y axis = SPEED TIME SPEED

  45. Object at Rest • The speed is zero and does • not change • Horizontal line (like a • distance – time graph y = 0 )

  46. Constant Speed HORIZONTAL • The line will be • The further the line is from the • the • it is moving. X - AXIS FASTER SPEED

  47. Speeding Up CLOSER • The line on a speed – time graph is • to the x-axis in the of the • time period when it has a speed. BEGINNING LOWER UPWARD • The line slants toward the • right side of the graph as the • speed . INCREASES

  48. Slowing Down • When initially starting to slow down the • point representing speed is • from the x-axis. FAR DECREASES • As speed the points • representing speed get • to the x-axis. CLOSER • The line on a speed-time graph slopes • to the right. DOWNWARD • When the line touches the x-axis, the • speed is and the object • stopped. ZERO

  49. Comparing Distance – Time and Speed – Time Graphs Objects at Rest

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