I'm a senior at a High School and in my AP Physics, we are having a chapter test regarding motion. We are using this textbook pictured below
[img_thumb]http://filesmelt.com/dl/physics.jpg[/img_thumb]
The special thing about our AP Physics class is that [b]it does not have calculus as a pre-requisite in joining the class[/b]. The major problem I have is that I am only taking Trigonometry this year. I know that Newton invented Calculus solely for Physics, but my teacher says that we will only be able to get up to precal [b]at most[/b] so there.
I'm still trying to understand how you understand acceleration, the differences between velocity, speed, displacement etc.
My teacher also told us about the four basic equations of kinematics/motion. My huge problem is trying to decipher word problems. I do not know how to plug in the variables and figure out which velocity is the initial or final.
Are there any 'Eureka' videos or guides that involve understanding these equations in a more easier way?
Draw pictures.
Ask your teacher.
Better than asking facepunch
Half of Facepunch isn't even in 12th grade yet.
[QUOTE=W00tbeer1;25347579]Half of Facepunch isn't even in 12th grade yet.[/QUOTE]
I want to ask the good half.
Draw pictures and make charts for your X, Y, and Actual values, especially when dealing with projectile motion.
[QUOTE=SteeleCratos;25347523]Ask your teacher.
Better than asking facepunch[/QUOTE]
My teacher had to take 2 and a half semesters to try to pass Calculus BC.
He also has trouble on half of the problems.
give an example of a word problem and i might be able to help
[QUOTE=W00tbeer1;25347579][b]85%[/b] of Facepunch isn't even in 12th grade yet.[/QUOTE]
Fixed.
acceleration- The change in Velocity
Velocity- The change in position (In a direction)
Speed- The change in position (No direction)
Displacement- The distance from initial to final points. Not necessarily the distance moved. You could run here, run back, and run here again, and the distance moved would be 3 lengths, but the displacement is 1 length.
Just read the book, calc isn't really needed, as long as you understand the terms. The only time I used calc was to do a shortcut for something you could do with physics understanding.
In his novel [i]From the Earth to the Moon[/i], Jules Verne describes a spaceship that is blasted out of a cannon, called the [i]Columbiad[/i] with a speed of 12,000 yards/s. The [i]Columbiad[/i] 900 feet long, but part of it is packed with powder so the spaceship accerates over a distance of only 700 ft. Estimate the acceleration experienced by the occupants of the spaceship during launch. Give your answer in M/S^2.
The problem is that out of the 4 equations I do not know how to derive them into different forms into what I am supposed to look for.
[QUOTE=CabooseRvB;25347277] I do not know how to plug in the variables and figure out which velocity is the initial or final. [/QUOTE]
Wait, what? Wherever it starts is initial, and final is where it ends. If it doesn't specify, it's either what you're answering, something not at all important, or something implied. Like if it says "The football moved 100m in the X direction, it means that Xi= 0, and Xf = 100
[editline]05:24PM[/editline]
[QUOTE=CabooseRvB;25347769]In his novel [i]From the Earth to the Moon[/i], Jules Verne describes a spaceship that is blasted out of a cannon, called the [i]Columbiad[/i] with a speed of 12,000 yards/s. The [i]Columbiad[/i] 900 feet long, but part of it is packed with powder so the spaceship accerates over a distance of only 700 ft. Estimate the acceleration experienced by the occupants of the spaceship during launch. Give your answer in M/S^2.
The problem is that out of the 4 equations I do not know how to derive them into different forms into what I am supposed to look for.[/QUOTE]
Yeah, the equations stuff is something you pick up on the way. The easiest way to do it is to use the equation that has the most stuff in it given, and then solve the other equations for what's left in the first one.
Also, what the fuck. Even if the shuttle is in standard measurements, why the fuck do they ask for the answer in metric. I hate it when they artificially make the problems harder with unit shitting.
[QUOTE=CabooseRvB;25347769]In his novel [i]From the Earth to the Moon[/i], Jules Verne describes a spaceship that is blasted out of a cannon, called the [i]Columbiad[/i] with a speed of 12,000 yards/s. The [i]Columbiad[/i] 900 feet long, but part of it is packed with powder so the spaceship accerates over a distance of only 700 ft. Estimate the acceleration experienced by the occupants of the spaceship during launch. Give your answer in M/S^2.
The problem is that out of the 4 equations I do not know how to derive them into different forms into what I am supposed to look for.[/QUOTE]
you should be using the formula vf^2=vi^2+2ad
because it's being blasted out of a cannon, the spaceship starts at rest so vi=0, and your formula can be written as vf^2=2ad
solving for a gets a=vf^2/2d
vf=12,000 yards/s (convert to m/s)
d=700ft (convert to m)
dx/dt = v
dv/dt = a
d(1/2(v^2))/dx = a
Ah calculus fun subject.
CabooseRvB, listen to me. This is what you are looking for, really watch them!!!
It's over 100 videos about 10 minute each, but this guy know his stuff.
[url]http://www.khanacademy.org/[/url] , you have to scroll down.
Dude I'm in AP Physics and we finished kinematics like a month ago, and it's not even AP Physics C. Did you even take a general physics course before it?
A lot of things in physics you just have to understand. If you're having a hard time determining initial (the velocity in the beginning) and final (the velocity in the end) then I think you're going to have a very hard time in the class, as that doesn't even involve math yet.
[QUOTE=Twitch;25348675]A lot of things in physics you just have to understand. If you're having a hard time determining initial (the velocity in the beginning) and final (the velocity in the end) then I think you're going to have a very hard time in the class, as that doesn't even involve math yet.[/QUOTE]
I know what initial and the final velocities are. It's just the kinematic equations I was given and I have to choose out of the four and which one is suited to the numbers I'm given.
If you don't know where to start, time is the variable you should always have and if you don't have it you should be looking for it. Does that help any?
[QUOTE=CabooseRvB;25347769]In his novel [i]From the Earth to the Moon[/i], Jules Verne describes a spaceship that is blasted out of a cannon, called the [i]Columbiad[/i] with a speed of 12,000 yards/s. The [i]Columbiad[/i] 900 feet long, but part of it is packed with powder so the spaceship accerates over a distance of only 700 ft. Estimate the acceleration experienced by the occupants of the spaceship during launch. Give your answer in M/S^2.
The problem is that out of the 4 equations I do not know how to derive them into different forms into what I am supposed to look for.[/QUOTE]
Okay let me try to break it down for you.
I assume you know the following formula's:
v = a * t
s = v * t
s = 1/2 * a * t^2
(t = time, s = distance, v = velocity, a = acceleration)
First you figure out the time it took for the Columbiad to exit the cannon, and thus the period of time over which the acceleration took place.
The average velocity is the half of the final velocity, assuming the acceleration is constant (draw a v - t graph to make it clear)
So we have s = v.mean * t
We put in s and v.mean (v.mean = 1/2 v.final) and we get t.
So now we know the time over which the accelation took place.
Now we take the formula s = 1/2 * a * t^2, and since we now have t, and we already had s, we can figure out a.
i assume the four equations your teacher gave you were
d=t(vf+vi)/2
vf^2=vi^2+2ad
d=vit+(1/2)at^2
d=vft-(1/2)at^2
or any other forms of these
in all cases, if you have 4 out of 5 variables (time, displacement, final velocity, initial velocity, acceleration) you can solve the problem
I just write down everything I'm given. Then I write all the equations I think apply to the situation and that have relevant-looking symbols.
I keep doing that until I have the same amount of equations as I have unknown variables.
Then I use my superior math abilities to solve the unknown variables.
If the equations are too hard to solve, I'll probably try to do it graphically or something. Or if the problem's worded so that something simple can be assumed, like sinx = x for small x, I'll start entering such things in once I've noticed that I can't solve it otherwise.
This is my usual method in situations where I have no idea what to do. Usually I do, though, but I've gotten through a few exams with very good grades this way.
[editline]02:24AM[/editline]
Oh and you really do need to understand the terms. The difference between velocity and speed is small: velocity is a vector. If you're asked for the velocity of something, in addition to its speed you also give its direction - if only an approximate one, or even if it is in no other way significant.
If you are still having problems I don't mind teaching what I know from my regular physics course and current Calc-Based Physics class.
[QUOTE=Kabuto;25349116]i assume the four equations your teacher gave you were
d=t(vf+vi)/2
vf^2=vi^2+2ad
d=vit+(1/2)at^2
d=vft-(1/2)at^2
or any other forms of these
in all cases, if you have 4 out of 5 variables (time, displacement, final velocity, initial velocity, acceleration) you can solve the problem[/QUOTE]
My book has the equations set to X. That's just same as distance right, graph-wise?
[img_thumb]http://filesmelt.com/dl/kinematics.jpg[/img_thumb]
I'm taking Physics right now, isn't displacement the same thing as distance except it regards direction? Also if the object "starts from rest" it's Vi is always 0.
[QUOTE=CabooseRvB;25349353]My book has the equations set to X. That's just same as distance right, graph-wise?
[img_thumb]http://filesmelt.com/dl/kinematics.jpg[/img_thumb][/QUOTE]
How old are you when you are a senior at high school? Is it 18?
Just wondering because I did that last year and I've god damn forgotten it all :/
[QUOTE=W00tbeer1;25349482]I'm taking Physics right now, isn't displacement the same thing as distance except it regards direction? Also if the object "starts from rest" it's Vi is always 0.[/QUOTE]
Displacement is how far something is from its initial position while distance is how far an object traveled over a certain period.
Displacement can be a vector. When asked for the displacement of an object, you could answer "3 meters north, 4 meters west". Its distance from the original position would then be 5 meters.
Negative distance has no physical meaning, but negative displacement just means "the opposite way".
Or if an object goes 360 degrees around some point on a circular path, its displacement would be 0, the distance of that displacement 0 and the total travelled distance 2πr.
It's always made pretty clear what they're asking for in those problems.
[img_thumb]http://filesmelt.com/dl/test_page1.jpg[/img_thumb]
That's the right calculation for acceleration right?
[editline]05:59PM[/editline]
[img_thumb]http://filesmelt.com/dl/test_page1.jpg[/img_thumb]
That's the right calculation for acceleration right?
12000^2 isn't 144000.
convert everything to kgms units
700ft: 213.4 m
12000yd/s: 10973 m/s
vf^2 = vi^2 + 2ax
10973^2 = 0^2 + 2a(213.4)
120406729 = 426.8a
a = 282115 m/s^2 :pwn:
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