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Discover the fundamentals of physics through key principles from Galileo to modern theories like quantum mechanics, exploring concepts like light, atom models, and scientific hypotheses. Learn about the SI system units, Power of Ten notation, and criteria for accepting theories as physical laws. Understand kinematics in one dimension and the importance of reference frames and speed measurements in describing motion. Dive into the world of physics from the smallest particles to the vastness of the universe.
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Galileo Principle: -recognize that a scientific problem exists; -state a hypothesis, an educated guess about the problem; -predict the consequences of the hypothesis; -perform experiments to see if the predictions occur; -formulate the simplest general rule that organizes the hypothesis, predictions and experimental results into a theory.
Models of Atom JJ Thomson: PLUM PUDDING!
Models of Atom Ernest Rutherford: PLANETARY MODEL!
What is light? Huygens: No way! It’s a wave! Sir Isaac: PARTICLE! Albert Einstein and Max Planck: Guys, guys! You BOTH are right!
Is the following hypothesis scientific? • “The alignment of planets in the sky determines the best time for making decisions” • “Intelligent life exists on other planets in the universe” • “Life forms evolve from simple to more complex forms”
Which if these are scientific hypothesis? • Atoms are the smallest particles of matter that exist. • Space is permeated with an essence that is undetectable. • Albert Einstein was the greatest physicist of the twentieth century.
UNITS of SI system For now we are interested in the base quantities of length, time, and mass. In the SI system (formerly known as the MKS system), their units are: Quantity unit symbol length meter m time second s mass kilogram kg
1 meter (abbreviated m) was originally chosen to be one ten-millionth of the distance from the Earth’s equator to either pole (1790). 1 second (s) was defined as 1/86400 of a mean solar day.
Some Lengths or Distances Proton radius 10-15 m Atom 10-10 m Football field length 102 m Earth diameter 107 m Earth to Sun 1011 m Farthest galaxy visible 1026 m
Some Masses Electron 10-30 kg Proton 10-27 kg Mosquito 10-5 kg Person 102 kg Earth 6x1024 kg Sun 2x1030 kg Galaxy 1041 kg
Some Typical Time Intervals Lifetime of very unstable particle 10-23 s Lifetime of muon 10-6 s One day 10 5s One year 3x10 7 s Length of recorded history 10 11 s Life on Earth 10 17 s Age of Universe 10 18 s
What are the criteria for accepting a theory as a physics law? • What role does the prestige of the scientist play in accepting a theory as a physical law? • What is the height of typical person, in centimeters? The length of typical newborn baby? The typical height of a bedroom ceiling? • What is the typical mass of 6-foot tall male, in kilograms? Of a 5-foot 6-inch tall female in kilograms?
SUMMARY For a new idea to be accepted, it must (1) agree with the existing data; (2) make predictions that can be tested, and (3) have a scientific basis. The measurement system used in science is the metric, SI system, based on meter, kilogram, and second. The sizes of objects studied in physics range from entire Universe down to neutrons and protons.
Describing Motion:Kinematics in one dimension Kinematicsis a part of mechanics, which is the description of how objects move.
Translational motion
Speed Speed is a measure of how fast object moves, measured by a unit of distance divided by a unit of time.
Instantaneous Speed Average speed doesn’t indicate the different speeds that may have taken place during shorter time intervals.
Average Speed average speed = total distance traveled/ time elapsed Total distance traveled = average speed X time
