Conceptual Physics 12th grade Christ Chapel Academy
Table of Contents Title Page • Physics • About Science 8 – 13 • Linear Motion 14 – 26 • Projectile Motion
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
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.
Common Misconceptions • Physics is applied mathematics • Although mathematics is a language of physics, it is not the only way to study physics.
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.
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
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??????
The Scientific Method • Galileo Galilee and Francis Bacon are credited as the founders of the scientific method.
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)
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!
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)
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.
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.
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)
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.
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!
Answer to Bell Work • All of Them!
Review • Read pages: 6 – 7 in your text book • Work on problems 1 – 13 on pg. 8; write the questions and your answers!!!!
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.
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.
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.
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.
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
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
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
Average Speed Pyramid d_ v/t Distancespeed/time
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.
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).
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).
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!
Changing Velocity This occurs when either the speed of the direction (or both) is changing; then the velocity is changing.
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
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.
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.
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?
Acceleration = change in speed change in time A.) B.) The rates of speed are the same, thus the accelerations are equal!
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?
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.
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
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.
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)
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
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
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?
Assignments for Today: • Pg. 27 (questions 42 – 45; 47 & 48) • Read pg. 19 - 20
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?
Tonight's Homework • Review Questions: (pg. 40) problems 1 – 5 • Make sure that you have viewed the Khan Academy videos (vectors, acceleration, Usain bolt)
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)