can anyone show me an equation that engineers(any kind) do?

Answer 1

This is one that I use quite a bit, in both my teaching and consulting work:

N_f = (1/C) int (ΔK)^m da

The integral is definite and over the interval from a_i (starting crack depth) to a_f (final crack depth).

N_f is the number of stress cycles required to grow a stable fatigue crack from a_i to a_f, that is, its predicted cyclic life to failure.

C and m are the Paris Law parameters, which are experimentally-determined material properties.

ΔK is the cyclic stress intensity range, defined as:
ΔK = Y∙Δσ∙sqrt(π∙a)
where Y is the geometry function for the given component and crack location and shape, Δσ is the cyclic nominal stress range, and a is the instantaneous crack depth.

Answer 2

I like this 1.

P1/pg +V1^2/2g + Z1 +Hp = P2/pg +V2^2/2g + Z2 +HF

this is Bernoulli's equation for flow of a liquid through a pipe. not all factor need be used and some can be cancelled where necessory. details as follows.
P1= 1st pressure.
p= "rho" density constant for liquid. water = 1000
g= gravity constant 9.81 meters per sec.
v1 = 1st velocity.
Z1= 1st height differance from base.
HP= head of pump
P2 = 2nd pressure
V2 = 2nd velocity
Z2 = 2nd height
HF = friction head for pipe. (loss of head due to friction inside pipe).
This is used for calculating pump sizes, pipe diameters, pressures, head loss. This equation is commonly used in mechanical engineering during college, but it is not common use in the workplace. Hope i didnt scare you wit this 1.

Answer 3

G= 0.5325 A C P / sq rt T
This is the formula for the flow rate of air thru an orifice at sonic velocity.
G = pounds (weight) of air /second
A = area in sq. inches of the opening
C= orifice coefficient (0.61 for a sharp edge)
P = Absolute air pressure upstream of the orifice = pisa
Abs. press is gage press + atmos press, usually 14.7 psi
T = absolute temp. (F + 459) deg

Answer 4

My favorite, the Fourier transform

X(f) = int x(t) exp(-j*2*pi*f*t) dt
integral over -inf to inf

I'm an electrical engineer.

p.s. person above me, I use that all the time in signal processing.

Answer 5

This is my personal favorite, but I never use it in engineering. But it'll blow some engineers away.

http://imgs.xkcd.com/comics/e_to_the_pi_times_i.png

Answer 6

Any kind? how about area = width * length, watts = volts * amps, I imagine you are looking for something more interesting, but my mind has gone blank, sorry.

Answer 7

definition of electrical engineering
Ohm's Law
Voltage = Resistance * Amperes
V=I*R

Answer 8

E
-- = R
I

VA X .778 = Watts