Top 10 Formulas

[ExplodingBoy]

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Post your top 10 important formulas.
Just a disclaimer, these formulas only become useful if you are very comfortable around them, which only comes from lots of practice questions.

Our physics teacher gave us this list of the most commonly needed physics formulas:

10. m = -i/o (magnification)
9. 1/o + 1/i = 1/f (optics)
8. T = 1/f (SHM)
7. P = IV (electricity)
6. V = IR (electricity)
5. F = ma (force)
4. f = Av (flow rate)
3. d = (v1)t + 1/2 at^2 (acceleration)
2. v = (lambda) f (SHM)
and the number 1 formula....


1. d = vt

Now that you've read this list you're probably thinking... these all seem like easy, basic formulas. Thats because they are! Almost everything else can be figured out by manipulating these formulas and playing around with units to find out when to multiply and when to divide.

One final thing.... Whats the formula for the area of a sphere? We had an inclass problem about how loud something would be if you are 10m away and when you are 20m away, and i didn't take into account that the sound would expand out like a sphere.

 

[MDtoBe777]

The Intensity of sound falls off as 1/r^2. So, if you are increasing the distance from the source of the sound by 2 you are decreasing the intensity by 4.

Can someone confirm this?

 

[willthatsall]

10. PV = nRT (Charles' and Boyle's Laws also)
9. d = m/v
8. C = q/v
7. vf^2 = vi^2 + 2ad
6. F = kqq/r^2
5. KE = 1/2 mv^2
4. n = c/v
3. p^2 + 2pq + q^2 = 1 (Hardy-Weinburg)
2. P = F/A
1. Delta G = Delta H - T Delta S

 

[blebl34]

The Intensity of sound falls off as 1/r^2. So, if you are increasing the distance from the source of the sound by 2 you are decreasing the intensity by 4.

Can someone confirm this?

I believe so... I = Power / unit area....so if you consider the area to be surface area of a sphere (which i think you do) than area = 4(pi)r^2

therefore your partially correct i guess

 

[myodana]

P + pgh +1/2(pv2) = P + pgh + 1/2(pv2)
Bernoulli's Equation

 

[Medikit]

E=hf will help for one question on the mcat.. maybe. Easy one to remember, though

 

[AxlxA]

Decibals = 10 log (Io/I) this will be helpful for like one question but one point can be the difference between the 14 and 15!

standing wave(one that i always neglect): wavelength = 2L/n where n=1,2,3.. for opened(both ends) or closed(both ends).
If opened one end, then wavelength = 4L/n where n = 1,3,5..

 

[Clemson Doc]

F=Gmm/r^2 is an important one if you ask me.

 

[MoosePilot]

E=hf will help for one question on the mcat.. maybe. Easy one to remember, though

This is the one I've seen on each of the tests I've taken, too!

 

[jon0013]

is it me or have i not seen one bernoulli's formula question on the 7 or 8 diags TPR and AAMC diags i've taken...maybe it was in a different form...ahh better not jinx myself..

 

[dandelion]

is it me or have i not seen one bernoulli's formula question on the 7 or 8 diags TPR and AAMC diags i've taken...maybe it was in a different form...ahh better not jinx myself..

General knowledge of Bernoulli's formula was necessary on ONE question in 5R, I remember, the one where they asked about fluid pressure vs. diameter of a pipe.

Another one questioner:
v/c = (delta f)/f = (delta lambda)/lamda (doppler approximation)

And top formulas not already listed:
m1v1 + m2v2 = (m1 + m2)vf (completely inelastic collisions)
U = mgh (potential energy)

I can't think of any others!

 

[Pembleton]

I'd also add centripetal force equation

F=(mv^2)/r

 

[ArcherM2]

3. p^2 + 2pq + q^2 = 1 (Hardy-Weinburg)

Haha.

 

[AxlxA]

regarding
p^2 + 2pq + q^2 = 1

you just know mcat likes to stick these one liners in ur ass for good measures of you memorization of random knowledge.

i hate these questions.

One of my classmates in MCB136 discussion said this when we were talking about pH.

The David Hasselhoff equation:

pH = pKa + log(Boobs/ass) ... Base/acid. Forever imbedded into my memory now

Another formula:
F dt = dP --- IMPULSE

 

[DieselPetrolGrl]

lets not forget the 3 constant acceleration:
vf= vi+ a t
vf^2= vi^2 + 2 a delta X
delta x = v t + 1/2 a t^2


btw i love E=hf and c=fw!!!!
anyone want to post the electric field ones
all i can pull out is V=ed

 

[MoosePilot]

I'd also add centripetal force equation

F=(mv^2)/r

Everyone has seen the one where you set centripetal force equal to gravitational force and solve for the orbital velocity?

I forget exactly how it comes out and don't want to post what I think to avoid confusing you, but it's an interesting one. I like the way to derive v efflux too 🙂

 

[Gavanshir]

Bringing this back for good luck!

10) P = (ro)gy
9) Q = Av
8) L = lambda / 2
7) delta f / fs = v / c
6) torque = Fl
5) E = hc/lambda = hf
4) v^2 = Vi^2 + 2aX
3) V = k q1 / r
2) P = V^2 / R
1) B = [row]Vg

 

[Hemichordate]

F = qvb sin theta!

 

[Evergrey]

The Intensity of sound falls off as 1/r^2. So, if you are increasing the distance from the source of the sound by 2 you are decreasing the intensity by 4.

Can someone confirm this?

I just studied this 10 minutes ago:

Inew = Iold (Rold / Rnew)^2

(formula derived using the area of a sphere)

 

[RogueUnicorn]

Hard Work x Time = Results