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Physical Science 2 Mr. Steinken

Physical Science 2 Mr. Steinken. Chapter 2 Energy and Motion. Describing Motion. Motion is a change of position of an object. A reference point must be specified in order to determine an object's position Frames of Reference Distance is the measure of

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Physical Science 2 Mr. Steinken

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  1. Physical Science 2Mr. Steinken Chapter 2 Energy and Motion

  2. Describing Motion Motion is a change of position of an object. A reference point must be specified in order to determine an object's position Frames of Reference Distance is the measure of how far an object moved. Displacement is the distance and direction of an object's change in position from the starting point. Cal Stanford 1982

  3. Distance Time Graphs • The slope of a line (steepness) on a distance-time graph is equal to the speed. • Shallow slope is slower than steep slope faster slower Distance meters Standing still Time seconds

  4. Distance Time Graphs • What information is recorded on the x-axis? • How many minutes does each line represent? • In what units is distance measured on the graph? • The graphs represent three swimmers, What does the slope of the lines tell you about the swimmers?

  5. Which swimmer swam the fastest? • Which swimmer stopped for 10 minutes? • How far did the blue swimmer travel in 15 minutes? • What is the difference in distance traveled between the red and green swimmer?

  6. d v t divide multiply Calculating Speed • Speed (v)-the change in position of an object over time • speed = distance time • SI units = m/s • When working equations 1. Write the formula (1pt) 2. Label the variables that you know (1pt) 3. Plug variables into the formula (1pt) 4. Write the answer(1pt) and a unit (1pt)

  7. Example Problem: Speed A car travels 38 meters in 3 seconds. What was its speed? • When working equations 1. Write the formula (1pt) 2. Label the variables that you know (1pt) 3. Plug variables into the formula (1pt) 4. Write the answer(1pt) and a unit (1pt) 1. v = d/t 3. v = 38m/3s • d = 38 m • t = 3 s 4. v = 12.7 m/s

  8. Velocity • Velocity (v)-describes the speed and direction of a moving object. • Still calculated v = d/t • How do you change 25 m/s into velocity? • You can have constant speed but changing velocity

  9. Acceleration • Acceleration occurs when an object changes speed or changes direction. • Acceleration is the rate of change of velocity, and is calculated from this equation: (or) a = Dv/ t • SI Unit = m/s2 • Meter per second every second

  10. Example Problem: Acceleration A sled full of penguins goes from 12 m/s to 45 m/s over 4 seconds. What is the sled’s acceleration? 1. a = (vf – vi) / t • vf = 45 m/s • vi = 12 m/s • t = 4 s 3. a = (45 – 12) / 4 4. a = 8.25 m/s2

  11. Negative vs. Positive Acceleration • An object speeds up if its acceleration is in the direction of its motion. • An object slows down if its acceleration is opposite to the direction of its motion.

  12. ACCELERATION ANIMATION • Observe the animation of the three cars below. Which car or cars (red, green, and/or blue) are undergoing an acceleration? • Study each car individually in order to determine the answer. • Now that you've answered the first question correctly, try this one: which car (red, green, or blue) experiences the greatest acceleration?

  13. As a final test of your understanding, consider the position-time graph at the right. • Each one of the three lines on the position-time graph corresponds to the motion of one of the three cars. • Match the appropriate line to the particular color of car.

  14. Ball Drop & Acceleration • Describe the acceleration experienced by the ball as it’s dropped. • Label with positive & negative acceleration on an illustration of the bounce. • For conventions, as the ball travels down we say it has positive acceleration

  15. Force: a push or a pull exerted on an object A. movement depends on the net force (sum of all forces on the object) Inertia: the tendency of objects to resist changes in their motion (aka – Newton’s 1st Law) C. Friction: force opposing the motion between two touching surfaces

  16. Shooting Objects at RestThe object’s inertia causes it to remain still even when a bullet passes through it.

  17. IV. Gravity: attractive force between any two objects A. Mass and distance affect the amount of gravity B. Weight (W): the measurement of gravity’s (g) pull on an object. C. g = acceleration due to gravity on Earth = 9.8 m/s2 D. Equation: W = mass x g (SI Units = Newtons (N)) • Example: If a person has a mass of 73 kg, • what is their weight in Newtons? 1. W = mg • m = 73 kg • g = 9.8 m/s2 3. W = 73(9.8) 4. W = 715.4 N

  18. http://regentsprep.org/Regents/physics/phys01/velocity/default.htmhttp://regentsprep.org/Regents/physics/phys01/velocity/default.htm

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