Question

PLEASE, HELP ME WITH ANY OF THESE EXERCISES: 4, 5 OR 6

Answer 1

You might need specialized formulas for these.
Do you have an engineering handbook handy?

Answer 2

I might be able to work my way through #4 using dimensional analysis an basic physics principles, but I would hope that these are from a book that contains the relevant governing equations...

Answer 3

hey, you promised to help?!

Answer 4

My electricity and internet connection went out last night; I apologize.
Before I give this another try, can you let me know what resources you have available?
What course is this for? Do you have the textbook for it? Do you know what formulas and constants you need to solve these?

Answer 5

I honestly have no clue:( It's my friend's hw for Mechanical Engineering

Answer 6

Mechanical, ok, so they probably can be done (mostly) with basic physics.
I can't promise that I'll have one worked out very soon, especially if I have to look up formulas and constants along the way, but I'll start working on one and let you know how far I get.

Answer 7

Here's what I was able to find so far for #4.
This is a diffusion flux calculation using Fick's Law:
\[\large J=-D\frac{dC}{dx}\]
J=diffusion flux
D=diffusivity
dC/dx=concentration gradient

From the initial flux and gradient, you can solve for the initial diffusivity constant, D_1.
Then it becomes necessary to see how the diffusivity changes under the new temperature and activation energy conditions.

Answer 8

Alright, here's a little more information that should put everything together.
Here is the formula for the effect of temperature and activation energy on diffusivity.
\[\large D=D_0e^{-E_A/R \cdot T}\]
D=diffusivity
E_A=activation energy
R=gas constant = 8.314 J/(mol*K)

I think the way to go is to solve for D_0 first using initial conditions, then find the new diffusivity, D_2 using D_0 and the new conditions, then put that into the Fick's Law equation.

Answer 9

Have fun!