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Linear Motion

Linear Motion. Edison Business Mr. Marrero. What is kinematics?. Branch of physics that describes the motion of objects. Think of your lab. Average Speed. Definition - Distance covered in a period of time : Equation – v = average speed - (m/s) – meters per second

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Linear Motion

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  1. Linear Motion Edison Business Mr. Marrero

  2. What is kinematics? • Branch of physics that describes the motion of objects

  3. Think of your lab

  4. Average Speed • Definition - Distance covered in a period of time: • Equation – • v = average speed - (m/s) – meters per second • d = distance covered (m) – meters • t = time (s) - seconds

  5. Average speed v = average speed vi = initial speed vf = final speed Another Way

  6. Think of motion (Grab a white board) D D T T

  7. Think of motion D D T T

  8. Explain how this person is moving

  9. Calculate the average speed of the object during the first 2 seconds Think again – Typical Problem

  10. Calculate the average speed of the object between 2 seconds and 4 seconds Think again – Typical Problem

  11. Calculate the average speed of the object between 4 seconds and 8 seconds Think again – Typical Problem

  12. Practice

  13. Bellwork • Explain how you think the object in the following Velocity (speed) vs time graph is moving

  14. Speed Vs Time Graphs Slope Speed (m/s) Area under curve Time (s)

  15. a = D V = Vf - Vi D t t Definition – Rate of change of speed in a period of time. Equation – a = acceleration (m/s2) = meters per second2 Vi = initial speed or velocity (m/s) = meters per second Vf = final speed or velocity (m/s) = meters per second t = time (s) = seconds Acceleration

  16. What’s happening? Speed (m/s) Speed (m/s) Time (s) Time (s)

  17. What’s happening? Speed (m/s) Speed (m/s) Time (s) Time (s)

  18. Typical problems • Find the acceleration of the object

  19. Typical problems • Find the total distance traveled by the object

  20. Find the acceleration of the object the first second. • Find the distance traveled during this time.

  21. Find the acceleration between 1 and 2 seconds. • Find the distance traveled during this time.

  22. Find the acceleration between 3 and 4 seconds. • Find the distance traveled during this time.

  23. Find the acceleration between 5 and 6 seconds. • Find the distance traveled during this time.

  24. Find the acceleration between 6 and 8 seconds. • Find the distance traveled during this time.

  25. Find the acceleration between 8 and 10 seconds. • Find the distance traveled during this time.

  26. Practice

  27. To solve physics problems • Identify known variables with units • Identify unknown variables • Identify the proper equation • “plug in” numbers into equation • solve for unknown • round if necessary

  28. Average Speed • Definition - Distance covered in a period of time: • Equation – • v = average speed - (m/s) – meters per second • d = distance covered (m) – meters • t = time (s) - seconds

  29. Typical Problem • A race car runs 540 Km in 3 hours. What is the average speed of the car?

  30. Identify known variables d = 540 km t = 3 hrs Identify unknown v = ? Identify proper equation Plug in numbers Solve for unknown v= 180 km /hr Use the steps

  31. Example #2 • A plane takes 2 hours to travel from San Juan P.R. to Orlando FL. If Orlando is 900 Km north of San Juan, What is the average speed of the plane?

  32. Example #3 • A marathon runner maintains a constant speed of 7 m/s during a 1000 m race. How much time did it take the runner to reach the finish line?

  33. Example # 4 • What is the distance covered by jaguar after running for 10 seconds after Mr. Marrero at 1000 km/h.

  34. a = D V = Vf - Vi D t t Definition – Rate of change of speed in a period of time. Equation – a = acceleration (m/s2) = meters per second2 Vi = initial speed or velocity (m/s) = meters per second Vf = final speed or velocity (m/s) = meters per second t = time (s) = seconds Acceleration

  35. Example: • A train accelerates from rest to 18 m/s in 6 seconds. What is it’s acceleration?

  36. Example A race car decelerates from 30 m/s to 15 m/s in 5 seconds. What is it’s acceleration?

  37. Solve for Vf Vf = Vi + at Acceleration rewritten!!

  38. Example: • A rocket travels from rest with an acceleration of 10 m/s2. What is the speed of the rocket after 5 seconds?

  39. Example: • A ball rolls down a hill with an initial speed of 5 m/s. If the ball rolls with an acceleration of 10 m/s2, how much time does it take for it to reach a speed of 20m/s?

  40. Independent of Vf • d = distance or displacement (m) • Vi = initial speed or velocity (m/s) • t = time (s) • a = acceleration (m/s2) d = Vi t + ½ a t2

  41. Example: • A Plane accelerates from rest at 5 m/s2. What is it’s displacement after 10 seconds?

  42. Vi = initial speed or velocity (m/s) Vf = final speed (m/s) d = distance (m) a = acceleration (m/s2) Independent of time • Vf2 = Vi2 + 2 ad

  43. Example • A plane needs a speed of 80 m/s to lift off. If the track is 2 x 103m, what must its acceleration be to reach take of speed?

  44. Practice

  45. Free Fall • Free Fall – motion with no acceleration other than that provided by gravity

  46. a = g = 9.81 m/s2 All Falling objects in free fall accelerate at the same rate REGARDLESS OF THEIR MASS!!!!!!!!!! For all “free fall” problems’ assume: Gravitational Acceleration • a = acceleration (m/s2) • g = acceleration due to gravity (m/s2)

  47. Example: • A basketball is dropped from the roof of a coliseum. • a) What is the ball’s speed after 4 seconds? • b) How tall is the coliseum?

  48. Example: • A student drops a stone from a bridge into the river. • If it takes 25 seconds for the stone to hit the river, how tall is the bridge? • What is the speed of the rock when it hits the river?

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