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Post by XKnifeXBuu on May 30, 2005 12:16:31 GMT -5
just weird stuff you wouldnt know everyday bout lol...
Is it possible for Michael Jordan to really "hang in the air?"
Well, it depends upon what you mean. Since he is always under the acceleration of gravity, his speed is a line of constant slope. At the top, his speed is zero. However, compare the amount of time he spends in the top 15cm of his jump to the bottom 15cm of his jump (assume he can jump 76cm.)
Although the maximum range of a projectile in vacuum occurs for a launch angle of 45 degrees above the horizontal, many "long range" military guns fire at greater than 45 degrees to get longer range. Why? [Hint: consider the fact that the air density decreases with altitude.]
Since the air is less dense at greater altitude, there is less air resistance, so the projectiles can fire futher.
How do we know that physics is "correct?
We don't. All we can say is that the physics we know has been able to explain all of the tests (observations of the world) that we have thrown at it. If a new observation comes along, then the physics will have to be modified.
Universal Gravitation
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Post by XKnifeXBuu on May 30, 2005 12:23:46 GMT -5
Lets say that we have an object siting on the table. We will say that it has no potential energy. We aren’t going to move it to a lower elevation.
Since it is not moving, it makes sense to define the body as having zero kinetic energy.
KE=0
Notice that this makes sense- if it is not moving, it has no energy of motion. It implies that there can be no negative kinetic energy. In other forms of energy, we can say that something has a negative amount, because these other forms are relative. (You will see later. See Potential Energy) Kinetic energy is more absolute.
[Notice, however, that it is not completely absolute. Right now, as you sit at the computer reading this, you may not seem to be moving, but we are really moving through space at a high speed as our planet go all around the sun, and the sun moves around the galaxy, etc. So KE may be relative in the grand scheme of things, but absolute in any particular reference frame.]
So now we want some way to calculate the kinetic energy of some body. Pretend that it starts at rest. If we move it horizontally without any energy loss (frictionless surface), all the work (Force over a distance) we do will be put into it will be converted to kinetic energy. So all we have to do is find some sort of formula that will calculate this for us.
To begin, start with this equation. It is the only one that does not involve time, so we use it because the time the forces are applied for does not matter.
v2 = v02+2ad
Since we are starting from rest, v0 = 0 and the equation becomes
v2 = 2ad
We use Newton’s second law (F = ma) solved for a (a = F/m) to substitute in for a.
v2 = 2(F/m)d
We do a little rearranging
½mv2 = Fd
We know that the force we apply exerted over a distance is the amount of work that we put in, so
½mv2 = W
And we know that the amount of work that we put in is equal to the kinetic energy (see above), so
½mv2 = KE
And we have it. A formula to find the kinetic energy of any body based on its velocity.
KE is a scalar quantity. Whenever we say v2, we really mean the magnitude of the velocity squared. (Technically, you could say that it is the dot product of velocity with itself. But if you aren’t a vector product person, don’t worry about it.)
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Post by mscupcke on May 30, 2005 13:58:01 GMT -5
[glow=red,2,300]my head hurts[/glow]  |
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Post by XKnifeXBuu on May 30, 2005 13:58:42 GMT -5
[glow=red,2,300][/glow]
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Post by mscupcke on May 30, 2005 18:04:49 GMT -5
sigh, if theres one thing i do well, its read
so yes, i did read it, but something is awry with me today... so my brain didnt process it...
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Post by XKnifeXBuu on May 30, 2005 18:07:43 GMT -5
lmao o ok that explains everyday then  |
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Post by mscupcke on May 31, 2005 1:16:00 GMT -5
no it does, seriously, my face, was tingling all day... no clue what that means.... but its still freaking tingling
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Post by XKnifeXBuu on May 31, 2005 2:39:20 GMT -5
haha ooooooooooo   |
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Post by mscupcke on May 31, 2005 15:18:19 GMT -5
yep... still tingling... i am gunna google it
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Post by XKnifeXBuu on May 31, 2005 15:26:29 GMT -5
::)lmao is it just cuase im blowing your blonde moments apart or is it just cause u drink too much? lol
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Post by mscupcke on Jun 1, 2005 7:30:24 GMT -5
nah, i cant drink, and my blonde moments have no effect on me, so its gotta be something else
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Post by XKnifeXBuu on Jun 1, 2005 13:06:56 GMT -5
o must be too smart?
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Post by mscupcke on Jun 1, 2005 20:09:05 GMT -5
oh yeah, thats it, i am too smart for physics.....
psh right
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Post by XKnifeXBuu on Jun 1, 2005 20:23:22 GMT -5
no i was saying i was too smart.... haha  |
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Post by mscupcke on Jun 2, 2005 9:04:25 GMT -5
hmmm youre too smart for what? physics? or my brain?
psh to that, i bet i am smarter than u
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