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Conceptual Physics

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  1. Conceptual Physics 12th grade Christ Chapel Academy

  2. Table of Contents Title Page • Physics • About Science 8 – 13 • Linear Motion 14 – 26 • Projectile Motion

  3. Objectives Chapter 1: About Science • Explain why physics is the basic science • Outline scientific method • Distinguish among observations, facts, hypothesis or laws and principles • Distinguish between science and technology • Distinguish among science, art and religion

  4. Common Misconceptions • Physics is the most difficult of the sciences. • Physics is the most basic of the living and nonliving sciences. • Physics has traditionally been more demanding of students than “easier” chemistry and biology courses, because more understanding of the subject is expected in physics.

  5. Common Misconceptions • Physics is applied mathematics • Although mathematics is a language of physics, it is not the only way to study physics.

  6. The Basic Science --- Physics • Science can be placed within two categories: living and nonliving things – the life sciences and the physical sciences. • Life sciences include: biology, zoology, and botany • Physical sciences include: geology, astronomy, chemistry and physics.

  7. The Basic Science --- Physics • Physics is the basics of all the physical sciences! • It’s study includes motion, forces, energy, matter, heat, sound and light. • Biology addresses the WHAT • Chemistry addresses the WHY • Physics address the HOW • Physics Chemistry Biology

  8. Mathematics – The language of Science • Sciences, like physics, that can be expressed in mathematical terms are unambiguous. • When there are findings in nature that can be expressed mathematically. They are easier to verify or disprove by experiment. • Why??????

  9. The Scientific Method • Galileo Galilee and Francis Bacon are credited as the founders of the scientific method.

  10. Con’t The Scientific Method • The Scientific Methodis a logical procedure for choosing an answer to a question. • Why is there a need for the scientific method? • There are no set order activities, individuals will do these following preliminary steps. • 1. Define the problem (narrow) • 2. Research the problem (has anyone else explored this?) • 3. Form the hypothesis (an educated guess) • 4. Perform experiments to test hypothesis • 5. State the outcome (hypothesis was accurate or found to be inaccurate)

  11. The Scientific Attitute • Fact……. An argument made by competent observers who make a series of observations of the same phenomenon. • Is a Hypothesis a FACT????? • When hypothesis are tested over and over and are not found to be contradicted than they become laws or principles!

  12. Continue the Scientific Attitude • Note: a Fact is not immutable and absolute! • Scientists must be prepared to: • Change laws and principles when hypothesis are contracted by other evidences • Change or abandon an idea (something you imagine or picture in your head; Merriam-Webster, 2013) • Accept their findings (even when hypothesis is inaccurate)

  13. Finish Scientific Attitutes • Theory is used differently in science than in normal every day speech…….. • A scientific Theory, is a synthesis of a large body of info that encompasses well- tested and verified hypotheses about certain aspects of the natural world. • Theories can evolve over time…. Making them stronger for the science community. • Scientific attitudes demand order and uniformity.

  14. Scientific Hypotheses (Must be Testable) • Hypothesis are scientific when there is a link to general understanding of nature and follow a cardinal rule. • Cardinal Rule……. IT MUST BE TESTABLE!!!! • Testability is more important than Accuracy of a hypothesis. • Scientific hypothesis test for proving wrongness. • If there is no test for proving it’s wrong then it is not scientific.

  15. Hypotheses that can neither be proven wrong or right are not scientific…. Even if they sound scientific! • Ex. “The alignment of planets in the sky determines the best time for making decisions.” This is speculator…. • Speculation: something that cannot be proven wrong, nor can it be proven accurate. (remember the peanut butter and jelly sandwich)

  16. Bell Work Answer: • (1) Atoms are the smallest particles of matter. • This answer is scientific because there is a test for its wrongness. • The universe is surrounded by a second universe….. Has no test for possible wrongness and is therefore unscientific. • Albert Einstein was the greatest physicists…. Is an assertion (opinion) that has no test for possible wrongness.

  17. Science, Technology and Society • Misconception: science and technology are the same! • Science and technology are not the same! • Science is a “method” of answeringquestions (theoretical) • Technology is the “method” of solvingpractical problems. • Neither are good or bad. What people chose to do with them are good …… or bad!

  18. Answer to Bell Work • All of Them!

  19. Review • Read pages: 6 – 7 in your text book • Work on problems 1 – 13 on pg. 8; write the questions and your answers!!!!

  20. Answers from questions • The concepts of physics are the foundation of other sciences. • Math is unambiguous; English is more familiar. • It is a method that is effective in gaining, organization, and applying new knowledge. • No scientific facts can change, given compelling evidence • A strength; change can nurture growth.

  21. 6. A hypothesis is outside the domain of science if it has no wrongness test. 7. Science answers theoretical questions; technology solves practical problems 8. Both are creative and portray a realm of experience. 9. Science is the study of cosmic order; religion studies cosmic purpose. 10. To give citizens more power over nature and more responsibility.

  22. Chapter 2 Linear Motion • Motion is Relative • Everything moves!!!! • Even when we are at rest, we’re moving….. How? • Your text book may be at rest; however it is moving about 30 kilometers per second (km/s) relative to the sun. • Relative: regarded in relation to something else. • When we discuss the motion of something, we’re really describing its motion relative to something else.

  23. Cheetah’s • When we say that a cheetah is the fasted land animal and can travel 200 meters per (seven) seconds; we’re really saying it’s movement in relation (relative) to the Earth or ground. • When we discuss the speeds of things in our environment we mean speed with respect to the surface of the earth.

  24. Speed • Speed: is a measure of how fast something is moving. • Speed is the rate at which distance is covered • It answers the questions: How long? How Fast? • It’s the rate at which distance is covered • Rate: a quantity that is divided by time

  25. Con’t Speed average speed = total distance covered (km) (m) time interval (s), (min), (h) Instantaneous speed: is speed at any instant Transpose the equations! Distance = speed (x) time Time = distance time

  26. Solving Physics Problems If a cheetah can maintain a constant speed of 25 m/ s, it will cover 25 meters every second. At this rate, how far will it travel in 10 seconds? In 1 minute? What is the question looking for? (clue words) How far (distance) What do I know? Constant speed is 25 m/s What equation(s) will help me solve this problem? Distance = speed (x) time

  27. Average Speed Pyramid d_ v/t Distancespeed/time

  28. Answers to Bell Work Questions • Average speed = total distance covered = 35 km = 70km/h time interval 0.5h • (b) no, not if the trip started from rest and ended at rest, because any intervals with an instantaneous speed less than 70 km / h would have to be compensated with instantaneous speeds greater than 70 km/h to yield an average of 70 km/h.

  29. Velocity • The words speed and velocity are often interchangeable within our every day language. • Physics, however distinguishes between the two! • Speed = is a measure of how fast something is moving. • Velocity = is speed in a given direction • For instance: when we say a car travels 60 km/ h; we’re referring to its speed. However, if we say that a car is moving 60 km/ h to the north, then we are referring its velocity (specific direction).

  30. Speed is a description of how fast an object is moving. • Velocity is how fast and in What direction it moves. Constant Velocitya constant speed (remaining at the same speed; doesn’t go faster or slower) and a constant direction (within a straight line; never curving).

  31. For instance, a group of people may circle a track remaining at the same steady speed; however they do not have constant velocity. • Why? • Their direction of motion is changing!

  32. Changing Velocity This occurs when either the speed of the direction (or both) is changing; then the velocity is changing.

  33. Acceleration • Acceleration = the rate at which the velocity (speed and direction) is changing • Acceleration is a rate, it measures how the velocity is changing with respect to time • Acceleration = change of velocity time interval ΔV A / Δt

  34. Common Misconception • Acceleration is simple an increase in speed. • Acceleration is any change in speed, direction or both! • The key idea that defines acceleration is change! • Whenever we change our state of motion, we are accelerating.

  35. In physics there can be an acceleration or a deceleration. • Deceleration (negative acceleration): a large decrease in speed. • Example: a car goes from zero to 60km/ h in 5 seconds is accelerating. If the car slams on their breaks fast going from 60km to zero this is a deceleration.

  36. Example In 5 seconds a car moving in a straight line increases its speed from 50 km / h to 65 km/h, while a truck goes from rest to 15 km/ h in a straight line. Which undergoes greater acceleration? What is the acceleration of each vehicle?

  37. Acceleration = change in speed change in time A.) B.) The rates of speed are the same, thus the accelerations are equal!

  38. Bell Work Questions: • The speedometer of a car moving northward reads 60 km/h. It passes another car that travels southward at 60 km/ h. Do both cars have the same speed? Do they have the same velocity? • Suppose a car moving in a straight line steadily increases its speed each second, first from 35 to 40 km/h, then from 40 to 45 km/h, then from 45 to 50 km/ h. What is its acceleration?

  39. Answer to Bell Work • Both cars have the same speed, but they have opposite velocities because they are moving in opposite directions. • The speed increases by 5 km/h each 1-s interval. The acceleration is therefore 5km/h-s during each interval.

  40. Bell Work Start Homework Problems: • pg. 26 (questions 22 - 25; 34, 36, 37, 38, 39) This Week: • Thursday Chapter 2 Test • Check blog page for assignments, announcements and study guides

  41. Free Fall: How Fast • Consider this: an apple falls from a tree. • Does the apple accelerate? • The apple starts from a position of rest (it was resting on the tree); however it gains speed as it falls. • The gain of speed indicates that the apple does accelerate as it falls.

  42. Gravity causes the apple to accelerate downward ( ) once it begins to fall. • Note: air resistance affects the acceleration of a falling object • When air resistance is not a factor and gravity is the only thing affecting a falling object this is called Free Fall (free falling objects are only affected by gravity)

  43. Elapsed time: the time that has elapsed, or passed, since the beginning of the fall. • During each section of the fall the instantaneous speed of the object increases by 10 m/s. • The gain in speed per second is the acceleration. Acceleration = change in speed = 10m/s = 10m/s2 time interval 1s

  44. In free fall problems we represent acceleration with a (g) not an (a) because acceleration is due to gravity. • (g) = 10 m/s2 (more accurately is 9.8m/s2) • Instantaneous speed = acceleration x elapsed time • The instantaneous speed (v) of an object falling from rest after an elapsed time (t) can be expressed in equation form*V = gt

  45. Problem • What would the speedometer reading on the falling rock shown on pg. 18 (of your physics book) be 4.5 seconds after it drops from rest? How about 8 seconds after it is dropped? 15 seconds?

  46. Assignments for Today: • Pg. 27 (questions 42 – 45; 47 & 48) • Read pg. 19 - 20

  47. Bell Work Question 10/17/13 • Suppose that an airplane normally flying at 80km/h encounters wind at a right angle to its forward motion – a crosswind. Will the airplane fly faster or slower than 80km/h?

  48. Tonight's Homework • Review Questions: (pg. 40) problems 1 – 5 • Make sure that you have viewed the Khan Academy videos (vectors, acceleration, Usain bolt)

  49. Chapter 3: Projectile Motion • In the previous chapter we discussed motion involving a straight-line (linear motion). (ex. Cars going down a highway, etc.) • In this chapter we will discuss motion along a curved path (nonlinear motion)