Physics Ebook
(First year plus a
little more, last muddled up May 07. Skip down a few paragraphs to start actual
physics-- hit the page down key about three times to start mechanics, or click
on start.)
THIS IS MAINLY FOR FIRST-YEAR PHYSICS STUDENTS. If you are at Tri-C in the College Physics series or the General Physics series, this could be useful to you. Some of it may be easy for you, but other things are hard. Mostly algebra level, some calculus. You can avoid the calculus if you want.
(If you want to bypass mechanics, click on fluids & heat, electromagnetism, oscillations, waves, or quantum stuff. Don't go there until you know how to do problems involving forces and motion, known as mechanics in physics. If you want to look for a particular topic, you might want to look at my index.)
I am really Zogrseb from the planet, Ktoobirzp. I came back in time 50 of your Earth years, and
I took over the pitifully puny brain of Professor Fred Gram, Physics
Department, Metro Campus,
Everything below is guaranteed correct or double your money back. (Let's see, two times zero....) It was all written in Bill's Bloat-ware, then converted to hyper-primitive. (Yew no its rite if it past Bill's spell checquer.)
Cyber-phys fans: You can skip What is physics? Physics is everything. Chemistry is an application of the physics of the atom, biology is the chemistry of living things, poetry relies on the physics and chemistry of the brain (which we do not fully understand yet)….And by the way, stuff about the world that we do understand is not known with total certainty. Things which seem to be certain could be 99.9999…% certain in some cases, but it is not like math knowledge, which is true by the way the rules of the game are set up.
To do physics, you need to hone your mathletic
skills a little. Algebra, mostly, even if you are in a
calculus-based course. If you have been away from math for a few years,
try clicking on these sample math problems, but
skip this if you are a good mathlete, and go right to
the aftermath. There
are 10 kinds of people: those who know binary and those who don’t.
Consider a plan of study. (I know, BORING.)
In some courses it may be useful to memorize lists of things. In physics, do
VERY little of this. If you attempt to rely mainly on this type of learning, it
is a serious learning disability and you will not do well. Work on concepts: broad principles, relationships….Another
thing- speed reading is of little benefit, so be sure to
read slowly and thoughtfully, and
if you realize that you did not understand something, don't go on until you get
it. It builds up- just as you needed to know addition before learning
multiplication when you were in grade school, you need to know certain
fundamentals of physics before going too far. Do lots of problems, and teach
someone else how to do them. Then you will really know it.
All of the above could be useful before you start physics. Now here (below) is the actual course with a few little side trips added. Altogether it is a condensed, informal textbook. Go through it in approximately the sequence indicated, repeatedly coming back to this page. When you finish this force and motion stuff, go to fluids, heat, electricity and magnetism.
If there is a star * by a link, you need to know that topic. There is
a little trick you need to know about converting units: click on *units. Or get some *linear
motion ideas. Velocity and acceleration and all that, and
the equations to use when acceleration is constant. In other words, it
discusses the equations to use when the velocity Vs time graph is a straight
line. Free fall is an example: gravity causes the downward v to increase the
same amount every second.
Distance = vot + 1/2at2 is one of
the linear motion equations, valid only if a=constant.
I would like to point out some stuff about *vectors: mostly you need to get a vector additude, dude, and learn how to add them. (If you are not willing to work on these things, you have a badditude.) Forces are vectors. Add a 5 lb. force and a 3 lb. force and the sum can be anything from 2 to 8 lb., depending on the directions of the 5 & 3.
Here the horizontal 5 lb. is added to a 3 lb. slanted up and left, and the sum is the red one that is less than 5 lb. For example if 3 lb. is perpendicular to the sum, then Pythagoras will tell you that the sum is 4 lb. (If you do not see the triangle above, maybe your browser has been set to reject graphics. It can be reset to accept them- my non-fat graphics will not fill you up or slow you down: usually 1 to 3 kb each.)
The usual way to add the vectors above is by components. The 5 has (x,y) components =(5,0). Let's say
the 3 has been found by trigonometry to have components (-1.8, 2.4). If your trig does not give you a negative for
the x component, just stick the negative sign in there. If you have +5 for the x component of the one
vector, the other must be negative.
Then add:
(5, 0)
(-1.8, 2.4)
(3.2, 2.4) is the resultant or vector sum in component form. The square
root of the sum of the squares of these is the magnitude of the resultant, 4.
When you go ballistic, you will need to know how to do *projectile problems. For this you need to know about finding components of vectors using trig, and you need to know about linear motion. Go back to the previous paragraphs and click those if you don't know them yet. I have a little movie of kicking a football and you can adjust the vo and initial angle while it is playing. Click here, and if it doesn’t work, your browser does not have a new enough Flash Player installed.
Want to find out the pitfalls people run into when trying to science-out *forces & motion problems? S F=ma and and many common kinds of forces. Bold = vector. In writing by hand, use
Click on forces & motion above to find out how to find the acceleration
of things like the thing on an inclined plane shown below and lots more. 
Incidentally, some of the simplest ideas cause the most trouble. All forces come in equal and opposite pairs, for example. (So all forces in the universe add up to zero.) Once you get the hang of it, this is a really simple concept. But you might have to work hard at ridding yourself of some wrong-headed notions about force. It is something like being in the habit of misusing lie and lay but with more serious consequences. Bad habits are hard to break, so work on it. Try this: An insect goes splat on the windshield of a fast-moving car. Think about the force on the insect due to the car, and the force on the car due to the insect. Are these equal magnitude forces in opposite directions?
Another idea that might give you trouble: You know that when you quit pedaling a bike or pulling a wagon, the thing stops. So you have reason to believe that in the absence of a force, an object will slow down and come to a stop. This is wrong. A force (friction force in these cases) must cause the slow-down. With zero force, the thing would maintain constant velocity in a straight line, like a space probe in deep space, so far from any planet or star that the gravitational force on it is negligible.
Are you are going around in circles? Look into *circular motion. Next time you go into orbit, you will need to know more about the *gravity of the situation. Gravitational force in everyday life is simply the weight, mg, and g is constant if you stay on Earth. If that is all you want to deal with, do not click on gravitation. Gravity sucks, but this is a good thing- it holds Earth together and keeps it in a nice orbit around the sun. We would not exist without it.
About that insect question in that earlier paragraph- yes, those are equal and opposite forces. How about a rock hitting a pane of glass and the glass breaks. Is the force on the rock due to the glass equal and opposite to the force on the glass due to the rock?
Find out why play is work, and work is perhaps not work: *work and energy. Work moves energy from one thing to
another or from one form to another, and total energy is constant (although it
can be hard to keep track of it all. When energy is "used up," it is
usually converted to heat. It still exists- heat is a form of energy.) Lots of problems can be solved by
Eo + SW = E, where Eo
is the total initial energy of a system, SW is the total work done
on the system, and E is the total final energy of the system. This is very much
like bookkeeping: Eo is like the balance
at the beginning of the month, SW includes deposits (+) and withdrawals (-), and E is
like the final balance.
People interested in politics or football will need to know about *momentum. This is simply mass times velocity vector,
and it is of fundamental importance to our understanding of the universe, and
you won't get the full impact of its importance until you study quantum
mechanics. The total momentum (vector sum) of a system is constant if the
vector sum of all forces on the system is zero. This is a statement of the
conservation of momentum principle, and it is a biggie, very useful for
collision problems and more. Impulse =
change of momentum is similar to work = change of energy, except that impulse
and momentum are vectors. Impulse is force multiplied by the time the force
acts. More than one
force? Then use the vector sum of forces. So in general,
S(mvo) + S(Ft) = S(mv)
Thinking of a Madison Avenue career? Any spin doctor needs to know *torque and *rotations. (I just realized that if you actually find any of this amusing, you need help as much as I do.) Torque and angular acceleration are related similar to the way force and linear acceleration are related.
Put the right spin on things, but before you
spin out of control, check out *conservation of
angular momentum. That works like linear momentum, but it is conserved not
when
SF
= 0, but when St = 0.
And yes, the rock and glass forces a few paragraphs ago are equal and opposite. How about standing in an elevator- is your weight equal and opposite to the force of the elevator floor on your feet?
Now that you know about energy and angular momentum, you might want apply these ideas to elliptical orbits. When you play golf on the moon, the ball follows an almost parabolic path, but to be exact it is a portion of an ellipse. Planets follow elliptical paths. (Exactly? No, the pull of gravity from other planets shifts the path slightly.)
And about your weight and the force of the elevator floor on your feet two paragraphs ago: gotcha!(?) These are not necessarily equal. Your weight is a force of attraction to the Earth (gravitational force), so the equal and opposite force is a force on the whole Earth toward you. (Yes, Earth is attracted to YOU. You are unique, just like everyone else.) The elevator floor force on your feet is equal and opposite to the force of your feet on the floor. Take a scale on an elevator, and you will notice a reading higher than your weight when the elevator is accelerating upward and lower when accelerating down. A scale measures what we call the normal force, and for the usual zero acceleration case on a level surface, the normal force is equal to the weight.
Here is one that you don't need: calculating Inertia by a method not in your text. (Inertia is to rotational acceleration as mass is to linear acceleration, and inertia is proportional to mass, but it is also affected by where the mass is located.) Also some info on when a quantity undergoes exponential decay or exponential increase. And about simplifying 1+1=2 .(Math humor? Yecch.)
Here are some problem tests on applications of the principles. Your instructor may well have different sorts of tests in mind: derivations, explanations of how things are, etc. Take your pick of easy, medium, or hard (not very hard).
Here is a mind-boggler for you: (First, a little background: the neutrino is the tiniest of all the fundamental particles, and so very very difficult to detect. We get a huge flux of them from the sun, and they mostly go right through Earth as though it didn't exist-- and if this boggles your mind enough for one day, don't read on.) Anyway, here it is. If you wanted to cut a neutrino beam down to half its original intensity by use of a lead shield, it would require a thickness of 15 light-years!! Planet Earth is too thin by a factor of billions. (A light-year is the distance light travels in a year, 9.46 x 1015 meters or the distance of a few hundred-million trips around Earth.) The latest evidence (2001) is that neutrinos have a tiny mass. A really tiny mass, smaller than the electron mass by a factor of thousands.
Other mind boggling things about nature are found in special relativity and general relativity, in which the essence is explained with a little algebra.
This junk is by Fred Gram at
fredrick.gram at tri-c.edu (but use @, not at).
Hey- you want to sign up at Tri-C? This sounds like a crass commercial come-on …(tri-c,
get it?), but my salary is not affected if you do; my motive is that maybe I
would enjoy your participation in a physics class. And you can get a good
education here whatever you decide major in.
My next main page is on *flows of fluids, heat, and electric charge: how they are alike and how they differ. Much of technology involves managing the flow of these things, so this is a big deal. It includes non-flow cases as well.
Another main page is on *oscillations and waves. That is a big deal, too. Simple harmonic motion, sound, light….
Then we find that waves are particles and particles are waves: Check out quantum. This is where physics seems magical.
If you want to look up something in particular, you could look at my index.
I have a bunch of interactive Flash movies
that might be instructive. If they seem blank, get a free Flash Player from
http://www.adobe.com/
If you want a really big and useful collection of web sites on chemistry and physics, try this, and you can probably find what you want.
If you are from the
fredrick.gram @ tri-c.edu (remove spaces. This is my defense against spammer software that gets email addresses that are listed on the web).