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Motion, Forces and Energy

Motion, Forces and Energy. Chapter 1. Chapter 1: Motion Section 1: Describing and Measuring Motion. When is an object in motion? How do you know an object’s speed and velocity? How can you graph motion?. Section 1: Describing and Measuring Motion. Observing Motion:

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Motion, Forces and Energy

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  1. Motion, Forces and Energy Chapter 1

  2. Chapter 1: MotionSection 1: Describing and Measuring Motion • When is an object in motion? • How do you know an object’s speed and velocity? • How can you graph motion?

  3. Section 1: Describing and Measuring Motion Observing Motion: Motion: distance from another object changes • Reference Point • An object that appears to be in place or an object used for comparison to detect motion • Object in motion if it changes position relative (compared to ) the reference point • Relative Motion • Motion dependent on reference point • Example: sky divers

  4. Observing Motion • Common Reference Point • Nonmoving objects such as buildings, trees, and mountains • Moving objects could also serve as reference point; bird flying by hot air balloon • Earth is a moving reference point; moving around the Sun

  5. Section 1: Describing and Measuring Motion • Measuring Distance • International System (SI) : system of measurement used around the world • Meter: SI unit of length

  6. Speed Depends on Distance and Time • Speed—the rate at which an object moves • Depends on distance travelled and time taken to travel distance • SI unit—meters per second m/s • The Speed Equation • Speed = Distance/Time • Example: 30m/5s = 6m/s

  7. Section 1: Calculating Speed • Average Speed • Average Speed = Total Distance/Total Time • Rate is not constant • Instantaneous Speed • Rate an object is moving at a specific time (at that instant)

  8. Section 1: Describing Velocity • Velocity: speed in a certain direction • Example 25 mph East

  9. Velocity: Direction Matters • Velocity Changes as Speed or Direction Changes • Velocity constant only if speed and direction do not change • Velocity changes if speed or direction changes

  10. Velocity: Direction Matters • Combining Velocities • Resultant Velocity • Combine the velocities if the velocities are in the same direction • Subtract the smaller velocity from the large velocity if traveling in opposite directions

  11. Section 1: Graphing Motion • Graph Motion on a Line Graph • X-axis: Time Y-axis: Distance • The slope (curve of the line) is the speed • Steeper the slope the faster the speed • Slope = Rise/Run

  12. Section 2: Slow Motion on the Planet Earth • How does the theory of plate tectonics explain the movement of Earth’s landmasses? • How fast do Earth’s plates move?

  13. Earth’s Plates • Plates: Pieces of earth’s crust broken into these pieces • Theory of Plate Tectonics • Earth’s plates move slowly in various directions; this has caused the movement of continents • Why Do Earth’s Plates Move? • Currents within the mantle are caused by rising hot molten rock and sinking cooler rock • New material at fault lines also cause movement

  14. Plate Movement • Plates move very slowly • Centimeters per year

  15. Section 3: Acceleration • What kind of motion does acceleration refer to? • How is acceleration calculated?

  16. What is Acceleration? • Acceleration: rate of the chance in velocity • Could: Speed UP • Could Slow Down • Could be a change in DIRECTION

  17. What is Acceleration? • Calculating Acceleration • Acceleration = final speed – initial speed / Time • SUBTRACT initial (starting)speed from the final (ending) speed and DIVIDE by the time • Example: Initial speed 0m/s; Final speed 10m/s; Time 5 seconds 10-0 / 5 = 2m/s2

  18. Acceleration: The Rate at Which Velocity Changes • Defining ACCELERATION • Acceleration: THE RATE AT WHICH VELOCITY CHANGES • Acceleration changes SPEED or TIME changes • Acceleration is also DIRECTIONAL changes

  19. Acceleration: The Rate at Which Velocity Changes • Calculating Acceleration Acceleration = final velocity – starting velocity time it takes to change velocity Acceleration expresses as m/s2

  20. Acceleration: The Rate at Which Velocity Changes • Examples of Acceleration • Positive acceleration: velocity INCREASES • Negative acceleration (deceleration): velocity DECREASES • Acceleration would also change if direction changes

  21. Acceleration: The Rate at Which Velocity Changes • Circular Motion: Continuous Acceleration • CENTRIFUGAL acceleration: acceleration that occurs in circular motion • Objects travelling in circular motion are always CHANGING velocity

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