posted on Apr, 14 2010 @ 11:05 AM
Hello there ats and welcome to the first and hopefully the start of mini series of posts attempting to teach the basics of physics. I am by no means a
pro, this is the first time I’ve really ever done anything like this, aside from teaching a friend a or two, so I don’t expect it to be the best
but I do believe it will be good for this site. I’m going to try to stay clear of as much high level math as possible, in order to give everyone a
chance to learn. If you would like more math involved let me know. I will also post problems for people to solve if wanted as well. If anyone wants to
maybe team up with me I wouldn't mind that either.
I have only borrowed the definitions and equations to explain, everything else is my writing and way of explaining.
Intro to physics part 1: Motion
Before we start I want to give a list of the variables we will be using so I don't have to explain during every segment.
v=velocity
x=distance
a=acceleration
s=displacement
Δ= A change in (Δ is known as the greek alphabet letter Delta)
Motion
Motion is the action or process of moving or of changing place or position; movement. Motion was one of the earliest studies in physics and without
what we know about motion now the world could have been a different place. Motion involves everything we will cover in this, which is quite a bit so
lets get started.
Displacement
A displacement is the shortest distance from the initial and final positions of a point P. It can be the length of an imaginary straight path,
typically distinct from the path actually travelled or it can be as simple as this scenario.
You are standing at a spot you turn east and walk 3 ft. You then turn around and walk 10ft west. From your original starting point you have travelled
a distance with a displacement equal to 3ft-10ft which of course equals -7ft. Displacement can produce both positive and negative answers.In physics
displacement is usually shown as the variable (s). Displacement is what is known as a vector, which is a quantity, such as velocity, completely
specified by a magnitude and a direction. There are different equations for displacement in different scenarios such as linear motion and non linear
motion which we will come back to later.
Speed, Velocity and Acceleration.
Assuming those reading this already know what these are I will skip defining them. Speed=distance/time
Speed is only a magnitude without a given direction therefore you will see velocity (v) used a lot more as it defines an object in motion, travelling
in a direction. With this being said we can rewrite our equation as follows: v=Δx/Δt or (Velocity= change in distance / change in time or
v=(xf-x0) / (tf-t0)
I like to write the equations out in each way because some people are more comfortable reading it some ways more than others.
When referring to non uniform motion Δv=vf-v0
Eventually you will be asked for certain speeds rather than an overall speed. Average, uniform and instantaneous speeds are what I am referring to.
None of these are the slightest bit difficult to figure out but it is good to know differences and how to get your answers.
Instantaneous Speed is your exact speed at any given moment. If you are driving and you happen to look at your tachometer or if you happen to
pass a police radar that lets you know your speed and it says 65mph, your instantaneous speed is 65mph. Uniform speed refers to a constant
speed.
Figuring out your average speed is a bit more work than these but still pretty easy. Let’s say you travelled 1000 miles in 3 days. To find your
average speed in mph you would first take 1000 and divide by 3, which is equal to 333.33 miles per day. In order to get to per hour and not day we
instead multiply (1000/3) by (1/24), which is 1000/72, which is roughly 13.88 mph.
Acceleration, which I'm sure most of you know, is any change in velocity whether it be an increase or a decrease.
The equation used for finding acceleration is a=Δv/Δt or a=(vf-v0) / (tf-t0)
Acceleration is characterized by units such as mph, mps and so on. In order to calculate units of acceleration use distance/time (squared).
Acceleration, just like velocity and speed, can also be measured as an average or instantaneous answers as well.
In order to find the average acceleration we just use the equation
ā = (vf-v0) / (tf-t0)
The variable ā = Average acceleration.
With all we have covered so far you can now find a way to relate these and solve equations with given information. I want to stop here because it will
be easier for me to group the next few things together and leave these as are. The way my teacher taught this was he basically gave us the info here
and left it up to us to figure out how to switch them around to figure out how to solve different problems.
I’m done for now though as I really want to see what people think.
PLEASE tell me what you guys think. I know this was somewhat brief but if you guys think this could be something worth continuing I will make sure to
make them worth it.
If enough people enjoy, I will start the next part right where I left off. I will explain some of the more advanced equations you can form with info
given here and I will have practice problems and such to further explain. For now you guys can go look online for some problems.
Part 2 would also include a more detailed look at vectors, Newton's laws explained in depth, momentum, angular momentum, laws of orbit, gravitational
pull and collisions. Which would pretty much finish up motion so I would go to thermodynamics after.
-Seangkt
[edit on 14-4-2010 by seangkt]