Transcript What is Physics?

Objective # 1: What’s Physics?
Definition of Physics
Branches of Physics
The Role of Physics in the “Real World”
Science and Engineering
What is Physics?
…What isn’t Physics?
Physics is all around us. It is in the electric
light you turn on in the morning; the car you
drive; your wristwatch, cell phone, music
player, and that big plasma TV set.
It makes the stars shine every night and the
sun shine every day, and it makes a football
soar between the uprights.
Branches of Physics
Kinematics
Mechanics
Heat (Thermodynamics)
Sound, Light, and Optics
Electricity and Magnetism
Atomic physics / Nuclear physics
Quantum Mechanics / Elementary Particle physics
Physics provides an important foundation for of all
other sciences—such as chemistry, material
science, geology, and biology.
Physics Defined
Physics is the science of energy and forces.
…it also addresses the fundamental properties of
matter, space, and time.
It explains ordinary matter as combinations of a
dozen fundamental particles (quarks and leptons),
interacting through four fundamental forces.
It describes the many forms of energy—such as
kinetic energy, electrical energy, and mass—and the
way energy can change from one form to another.
It describes a malleable space-time and the way
objects move through space and time.
The Role of a Physicist
They work for research laboratories,
universities, private companies, and
government agencies.
They teach, do research, and develop new
technologies.
They do experiments on mountaintops, in
mines, and in earth orbit.
Physicists are good at solving problems—all
kinds of problems, and use mathematics to
solve these problems.
Role of Physics in Science and
Engineering:
Materials and objects behave and interact in
very reliable ways – they way they move,
accelerate, push on each other, heat up, emit
light, or even make music.
We call these predictable behaviors “laws of
physics”
Our understanding of physics has led to the
development of techniques and technologies
and advances that have revolutionized human
lives.
Devices Derived from Physics
Research:
Satellites and Spacecraft
Medical Devices:
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MRI (magnetic resonance imaging)
CT Scan
X-rays
PET Scans
Synchrotrons and Accelerators
Microwave ovens
Smoke Detectors
Transistors and IC chips
Lasers
Television, radios, Electronics
What will you do in this class?
Think Critically.
Generate Questions.
Work with a team.
Engineering and Creative Problem Solving
Reflect on your experiences with experiments.
Discuss results from experiments.
Solve Problems
Put your results into words.
Create graphs to display your data.
Interpret graphs to analyze your data.
Use math to describe relationships between
variables.
Physics sounds difficult…
If you are proficient with algebra (and a
little trig), you can succeed.
If you are not, you can become so, and
then succeed.
Must be patient and work hard.
Objective # 2:
Basic Vocabulary
Physics:
The study of energy and forces.
Physicists ask:
Why does that happen?
How does that happen?
Basic Vocabulary
Matter: Anything that has mass and volume.
Energy: The ability to do work
(to change or move matter).
Law of Conservation of Energy and Matter:
Energy and Matter are neither created nor
destroyed but only changed in form.
* (Matter and Energy are actually interchangeable,
but that is a special circumstance!)
E = mc2
Basic Vocabulary
Hypothesis:
An educated guess.
Scientific Theory:
A possible and logical explanation of why or
how an event occurs, which has no
contradicting evidence.
Scientific Law:
A repeated observation of a natural event that
is reliable without exception.
(Does not explain why or how!)
Scientific observations
Subjective observation (qualitative)– is observed
depends upon opinion.
Examples:
It's hot in here.
He’s tall.
It’s dark red.
Objective observation (quantitative)-- is measured.
It is factual.
Examples:
It's 22oC in here.
He’s 1.9 meters tall.
It reflects 560 nm lightwaves
The next objectives are addressed in the
Measurement Notes
(the slides that follow are overview of
some of the main branches of physics)
Mechanics
Developed by Sir Isaac Newton in the 17th century, the
laws of mechanics and the law of gravity successfully
explained the orbits of the moon around the earth and
the planets around the sun.
They are valid over a large range of distances: from much
less than the height of an apple tree to much more than
the distance from the earth to the moon or the sun.
Newton’s laws are used to design cars, clocks, airplanes,
earth satellites, bridges, buildings—just about everything,
it seems, except electronics.
Electromagnetism and Electricity
Electricity is another example of physics, one that you
may experience as a spark when you touch a
doorknob on a dry winter day.
The electrical attraction of protons and electrons is the
basis for chemistry.
Magnetism is another force of nature, familiar to us
from refrigerator magnets and compasses.
In the 19th century, James Clerk Maxwell combined
electricity and magnetism. He showed that light is an
electromagnetic wave that travels through empty
space. (Waves had always required a medium, for
example, water is the medium for ocean waves.)
Quantum Mechanics
Einstein went on to replace Newton’s theory of gravity with
his general theory of relativity, which says that space and
time are changed not only by speed, but also by the
presence of matter.
Imagine space-time as a large sheet of rubber, and set a
bowling ball on the sheet; it will be dimpled near the ball. A
tennis ball rolled slowly near the bowling ball will curve
around it and may settle into an orbit, just as the earth
orbits the sun.
Today, the general theory of relativity is well-tested and is
used to accurately determine the location of your car if you
have a GPS (Global Positioning System) device.
Nuclear Structure
Quantum mechanics describes how electrons can only
travel around the nucleus of an atom in orbits with
certain specific energies.
When an electron jumps from one of these orbits to
another, the atom will absorb or emit energy in discrete
bundles of electromagnetic radiation.
Because the energies of different states of an atom are
known with high precision, we can create highly
accurate devices such as atomic clocks and lasers.
Transistor Theory and Quantum
Mechanics:
Quantum mechanics is also necessary to understand
how electrons flow through solids.
Materials that normally do not conduct electric current
can be made to conduct when “doped” with atoms of
a particular element.
This is how we make transistors, microscopic
electrical on-off switches, which are the basis of your
cell phone, your iPod, your PC, and all the modern
electronics that has transformed our lives and our
economy.