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Summer Physics Bootcamp

Summer Physics Bootcamp. Instructor: Jeff Ciaccio, BS, BSChE, MS, MSACS “Jeff”, “Mr Jeff”, “Mr C”, “Ciaccio” (See-ah-co) are all fine. Contact Information. www.MSEAcademics.com. Cell:770-401-6731 Jeffcia@MSEAcademics.com. Warm up.

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Summer Physics Bootcamp

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  1. Summer Physics Bootcamp Instructor: Jeff Ciaccio, BS, BSChE, MS, MSACS “Jeff”, “Mr Jeff”, “Mr C”, “Ciaccio” (See-ah-co) are all fine

  2. Contact Information • www.MSEAcademics.com • Cell:770-401-6731Jeffcia@MSEAcademics.com

  3. Warm up • You walked 0.5 miles north, 1.2 miles west, 0.8 miles south, and 1.6 miles east. • find the total distance traveled (is this a scalar or vector?) • find the vector showing where you ended relative to where you began.

  4. Warm up

  5. Warm up

  6. Warm up So, how far north/south, and how far east/west? Use Pythagorean Thm and SOHCAH TOA

  7. Warm up Can you see this is exactly the same vector even though the triangle has been drawn differently? (0.4mi)2 + (0.3mi)2 = c2 = 0.25 mi2 so the magnitude (length) = 0.5 miles

  8. Distance and Displacement

  9. Distance and Displacement • Find the slope for each of the three areas of the following graph. Include the units and the sign. Describe what happened in the three different sections including speed and direction. • Find the average speed and velocity for the whole time.

  10. Distance and Displacement

  11. Distance and Displacement • Find the slope for each of the three areas of the following graph. Include the units and the sign. Describe what happened in the three different sections including speed and direction. • Find the average speed and velocity for the whole time.

  12. Distance and Displacement

  13. Know the definitions!! • There are several definitions that you must know very well! Displacement, distance, speed, velocity, acceleration, slope. • There are also several that are more subtle: vi, vf, vavg, Dv, etc. • Physics is NOT about just finding the right equation!! It is NOT a math class!

  14. In your own words… • On paper, write what you think acceleration is. • What do you think the units for acceleration are (several correct answers). • Hint: if you are at a red light, and then you accelerate, what are you doing? • Try to think of different ways you can accelerate.

  15. Acceleration • acceleration is a vector. That means that it can be positive, negative, and it has a direction. • acceleration: the rate of change in velocity. • a = Dv/t • If something is changing direction, it is accelerating (even if the speed is not changing).

  16. Displacement: Easy case • If you drive at a constant 50mph north for 30min, find your displacement and distance traveled. • Always, always, always check to make sure units are consistent. Or even better, use them in your equations.

  17. Displacement:Easy case • If you drive at an average of 50mph north for 30min, find your displacement and distance traveled.

  18. Displacement:Easy case • Find the area under both “curves”. And yes, a straight line is called a curve. 

  19. Average Vel: Easy Case • If the acceleration is CONSTANT then (and only then) can you can find • This is the case 99% of the time even in a calculus based class.

  20. Neg in physics • A negative sign in physics almost always means the opposite direction. • A negative acceleration does NOT mean something is slowing down!! • On your paper: You are going 5m/s to the west and accelerating at 1m/s per second. What is your velocity after 10 s? Make east the positive direction. see www.physicsclassroom.com/mop

  21. Common Misconceptions(On your paper, List all that apply) • Can an object be moving upward with a downward acceleration? • If you throw an object straight up, what is it’s velocity at the peak height? it’s acceleration? • Name 3 controls in a car that cause it to accelerate • If an object is accelerating, what MUST be true?

  22. Common Misconceptions(On your paper) • If an object is accelerating, what MIGHT it be doing? • If an object is NOT accelerating, it MUST be: a) maintaining a constant vel, b) be at rest, c) moving at constant, non-zero, speedd) changing direction • A car is moving to the west at 40mph and slowing to 30mph. Its acceleration is (be as specific as possible)

  23. Common Misconceptions(On your paper) • A car is moving to the west (take east to be the positive direction) at 10m/s. If it accelerates at -bb2m/s per second for 10s, what is its velocity? What is its speed? • A car’s velocity after each consecutive second is 2m/s, 4m/s, 6m/s, 8m/s, etc. This car is moving with a constant __________.

  24. Common Misconceptions(On your paper) • A car moving at a constant velocity of 10m/s east for 5 seconds has an acceleration of _________. • A car moving at 20m/s west, then 18m/s west after 2 seconds has an acceleration of _________. (A positive direction has NOT been established).

  25. Common Misconceptions(On your paper) • Which are units of acceleration? (m/s)/sm/(ss)m/s2(m/min)/smph/s m/smi/s all of these?

  26. Common Misconceptions(On your paper) • a car with rightward velocity and leftward acceleration is moving in which direction and speeding up/slowing down.

  27. The “Big 4” Dd Dv Vavg * t a * t Dd = vit + ½ at2 vf2 = vi2 + 2aDd

  28. Use them in the order presented • You can use any equation as long as there is only 1 unknown. • Watch your UNITS!! Units must be consistent to cancel them out. • Watch for vectors that must be broken into their componenets • Try to use the equations in order

  29. Fill in the table • Write the table this way

  30. 1 Dimensional Examples • If you travel at an average of 10m/s for 2 min, how far will you have gone? • The only things we know are vavg and t. • Convert units first: t = 120s

  31. 1 Dimensional Examples Dd Vavg * t Cover up the Dd, which shows you to multiply vavg and t. 10m/s * 120s = 1200m Use your dimensional analysis just like in chemistry!! Cancel the s’s

  32. 1 Dimensional Examples • A ZX6 accelerates from rest to 20m/s in 3.0s. Find the acceleration and the distance. • All units are consistent with each other

  33. 1 Dimensional Examples Dd Dv Vavg * t a * t We have enough information to use the first both magic triangles. Notice that the avg vel is just 0 + 20 over 2 and delta v is vf – vi Delta d = 10m/s * 3 s = 30m a = Dv/t = ( 20m/s ) / (3 s) = 6.67m/s2

  34. 1 Dimensional Examples • An F-22 Raptor accelerates at 5m/s2 from 20m/s to 120m/s. How long did it take, and how far did it go?

  35. 1 Dimensional Examples Dd Dv Vavg * t a * t We don’t have enough information to use the first magic triangle, but we can solve for time with the second and then go back to the first. t = Dv/a = 20s Dd = vavg * t = 70m/s * 20s = 1400m

  36. 1 Dimensional Examples • An F-22 Raptor accelerates from 20m/s to 120m/s in 1000m. How long did it take, and what was its acceleration?

  37. 1 Dimensional Examples Dd Dv Vavg * t a * t We can use the first magic triangle to find time and then the second to find acceleration t = Dd/ vavg = 1000m/70m/s = 14.29s a = Dv/t = ( 100m/s ) / (14.29s) = 7m/s2

  38. Gravity and little g • Gravity is a FORCE. • Objects with more mass will have a greater gravitational force (weight) • Objects near the surface of the earth will ACCELERATE at a constant 9.8m/s2. This is “g” the acceleration due to gravity. NOTE: This is NOT “gravity”

  39. Gravity and little g • g will be different on different planets/moons/locations. • g is slightly different at sea level or on a mountain top, but it is very slight, so most teachers will allow you to use 9.8m/s2 (or even 10m/s2 sometimes) • g is negative ONLY because we normally take up to be the positive direction.

  40. 1 Dimensional Examples • You are on a cliff that is 100m above the ground when you throw a rock straight up at 12m/s. How long will it take to reach the peak (hint what is vpeak?). How high above the ground is that? How long would it take to reach the ground from the peak? What is the total time it spent in the air?

  41. Up to peak Dd Dv Vavg * t a * t We can use the second magic triangle to find time and then the first to find distance from the cliff.t = 1.224s Dd = 7.35 m

  42. Down from peak We finally get to a case where we need the 3rd equation Dd = vit + ½at2 and since vi = 0 Dd = ½at2

  43. Breaking up Problems Notice that we broke up the last problem into i) Up to the peak ii) Down from the peak This is a great strategy, but you must keep everything straight! Do NOT do things blindly in physics!! This can often make the math easier (like avoiding quadratic equations with linear terms).

  44. Minds On Physics • I highly, HIGHLY recommend that you use Minds On Physics to test your conceptual understanding before going on to more advanced problems. • www.physicsclassroom.com/mop • For tonight, try those in Mechanics>Kinematic Concepts

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