Stupid questions thread

[Anonymous No.10563263]

Why does the equation for drag coefficient have the 1/2 ?
Dimensional analysis doesn’t really help with this, the scalar simply doesn’t show up.

Also, stupid question thread, I guess.

[Anonymous No.10563266]

>>10563263
Oops. A/2, meaning 1/2 times A
Still, the question stands

[Anonymous No.10563383]

[math]p=\frac{\rho v^2}{2}[/math] is the kinetic energy per unit volume of a flow, called the dynamic pressure. Turns out drag force is proportional to dynamic pressure and the area of the face so that [math]F=C_dpA[/math] where [math]C_d=\frac{F_d}{pA}=\frac{F_d}{\rho v^2A/2}[/math] is a dimensionless constant we call the drag coefficient.

[Anonymous No.10563401]

>>10563383
I want to add that [math]C_d[/math] isn't so much a constant as it is a function of the Reynolds number, which is in turn a function of fluid properties, flow velocity, and the geometry of the body.

[Anonymous No.10563913]

>>10563383
>>10563401
Thanks anon. This was exactly what I was looking for

[Anonymous No.10564990]

how the fuck does it change for the sphere? it thought it was inherent to the shape

[Anonymous No.10565086]

>>10564990
See >>10563401
The charactaristics of the flow also matter, i.e. if it is turbulent or laminar or critical or transitional, etc.

[Anonymous No.10565115]

>>10565086
how come the other ones don't change then. clearly it changes vastly for others as well, its just not shown

[Anonymous No.10565157]

>>10565115
Because it isn't a very good chart. The value of [math]C_d[/math] changes for all numbers with change in [math]\text{Re}[/math]. When you look up a table of drag coefficients, you have to specify the Reynolds number. For a circle [math]C_d=.5[/math] for [math]\text{Re}\approx10000[/math]

[Anonymous No.10565987]

>>10563263
If you’re really interested in learning more, I’d reccommend boundary layer theory by Schlichting. The Indian edition is like 30 USD.

[Anonymous No.10566052]

Can anyone good with NMR tell me what the last equation under 'NMR lineshape' gives? I have no idea what F(omega) is.

[Anonymous No.10567182]

Can someone help me?

I'm trying to find a fit for this data, and my equation looks roughly like this:

[math] y = A(sin(cx)/cx)^2 [/math]

Where A and c are constants.

What can I do make the middle spike less intense compared to the others?

This is for single slit diffraction by the way.

[Anonymous No.10567187]

>>10566052
It's chemical shift

[Anonymous No.10567377]

>>10567182
stick a constant in front of the c in the denominator and make it very small

[Anonymous No.10567517]

>>10567377
The ratio in intensity between the middle peak and the second highest peak is about 20:1, and this does not change by giving the denominator a different constant (regardless of its value).

[Anonymous No.10567529]

>>10567182
you can never fit a sinx/x to this function
try cos(ax)^2*exp(-b*x^2) form of solution

[Anonymous No.10567567]

>>10567529
>cos(ax)^2*exp(-b*x^2)
Thanks man, this worked beautifully.

[Anonymous No.10567573]

>>10567567
damn, not even i expected it to work so well

[Anonymous No.10567629]

Newton's law of gravity: Fg = G * M1+M2/r^2
Law which describes how much 2 mass objects are attracted towards eachother.
So theyre always moving towards eventually touching eachother.
>r is now 0
>formula broke?

[Anonymous No.10567633]

>>10563263
What do you think?
Major: EE
Minor: Software Eng.
Master: Computer science and Math

[Anonymous No.10567739]

>>10567633
why study EE if you just wanna write code dawg

[Anonymous No.10567789]

>>10567629
When would r ever be zero? Two objects can't occupy the same position in space.

[Anonymous No.10567985]

>>10563263

The 1/2 shows up because 1/2 * rho * v^2 is dynamic pressure (q). Then you can express coefficient of drag as the drag force normalized by the product of dynamic pressure and reference area (CD = D / (q * A)). The 1/2 is mathematically arbitrary.

[Anonymous No.10567990]

>>10567739
He wants to be a full spectrum warrior

[Anonymous No.10568053]

How do I make induced pluripotent stem cells for therapeutic uses?

[Anonymous No.10568284]

>>10567990
Is it bad anon?

[Anonymous No.10569528]

>>10563263
What's the difference of force and momentum?

[Anonymous No.10569545]

>>10567789
Ok ill try to explain it better.
if the sizes of the mass are very small (point like), or if the 2 masses are very fucking big. the r wouldn't be 0, but very fucking small, thus the attraction force increases. Eventually before touching the 2 masses are attracted towards eachother with the force of infinite newtons before becoming literally unseperatable.

[Anonymous No.10569547]

>>10569528
Momentum is the mass*velocity. This is it's definition. A force is a push or a pull. The rate of change (the time derivative) of momentum of an object is equal to the sum of all forces acting on it. This is Newton's second law: F=m*dv/dt

[Anonymous No.10569707]

>>10569545
In general, Newton's law of gravitation breaks down on the very small scales and the very big scales. If the distance between the two masses is very small(on the subatomic level), then you would need a quantum theory of gravity, which we don't have currently.
A general rule of thumb in physics is that there are no infinities in nature.So, if an infinity, or something going to infinity appears in a theory, that is a sign that the theory is breaking down and needs to be replaced with a better theory at that point or limit.

[Anonymous No.10570298]

Please help I have an entrance exam in less than a month and I have no idea what I need to know or how I should even tackle this. Wtf is even the value of sin/cos (π/8)???? Is the only way to solve this to memorize?

Translation: the number √((2-√2)/(2+√2)) is equal to:

(a) tan π/4
(b) tan π/8
(c) tan π/12
(d) none of the above

[Anonymous No.10570408]

>>10567529
>>10567567
>>10567573
makes sense, gaussian profile, with oscillations