# Search results

1. ### Determining appropriate range from test data

Hello all. I am performing chemistry experiments and recording the times of various observed results. What I am doing currently is performing the test several times in order to determine what result is "normal." My goal is to determine a range as a standard by which all future tests will...
2. ### Method to remove salt from water (Not distillation or RO)

Hello all. I'm tutoring a high school student and am having trouble with a seemingly simple science project that was assigned: How to remove table salt from water. Having graduated as a Chemical Engineer, I said distillation! But the problem statement says you can't be that boring. Then I said...
3. ### Multiple Linear Regression (2 factors, 1 output)

Hello all; I'm doing work for my job, and I've forgotten my statistics =(. I first want to know if what I'm trying to do is possible. I want to create a linear regression of the form Y = a * x1 + b * x2 + c. http://imgur.com/Q4vGP" [Broken] As you can see, there is space that is...
4. ### Lin Alg Question: Cross-Product Proof

http://imgur.com/mceBq" [Broken] I'm curious to see if my conclusion is correct. thanks in advance.
5. ### Purging air from system

Here is the situation: We are building a small model car (roughly 8 in wide by 18 in long) whereby hydrogen is produced in a chemical reaction, travels through some tubing to our fuel cells, which in turn powers the motor. The issue lies in the start-up procedure; it is required to purge...
6. ### Fuel Cell Voltage Calculation

Hello, I'm doing work in Fuel Cells and am having difficulty with a simple issue; the Nernst Voltage (E) is greater than the Standard Potential (EO) The only electrochemical reaction considered is H2 + 0.5O2 --> H2O The Nernst equation for this reaction is E = EO - (RT / 2F) ln (PH2O / (PH2...
7. ### Recommended Physical Chemistry Text

Hello, I'm taking Physical Chemistry I in second year, and my prof does not have a required book for the course and everything will be based off his notes (which are very good by the way) However, I would like a deeper understanding of the material, and the prof did recommend two books. What...
8. ### Recommended Physical Chemistry Text

Hello, I'm taking Physical Chemistry I in second year, and my prof does not have a required book for the course and everything will be based off his notes (which are very good by the way) However, I would like a deeper understanding of the material, and the prof did recommend two books. What...
9. ### Capillary Tubes (purchase in Canada)

Hey everybody I'm looking to buy a set of these: http://www.sciencelab.com/page/S/PVAR/10615/10-2410 the 5mm OD tubes that become malleable when subjected to heat (for a little project I want to do). Unfortunately, this website does not ship to Canada. Anyone know of any brick & mortar...
10. ### Summation Proof with Binomial Theorem

Prove the following statement: $\sum\limits_{r + s = t} {\left( { - 1} \right)^r \left( \begin{array}{c} n + r - 1 \\ r \\ \end{array} \right)} \left( \begin{array}{c} m \\ s \\ \end{array} \right) = \left( \begin{array}{c} m - n \\ t \\ \end{array} \right)$ Any initial...
11. ### Repeatedly 'cosine'ing a number: convergence

A curiosity I've had recently... When repeatedly taking the cosine of a number in radians, it appears to converge to a value. i.e. cos(cos(cos(...cos(x)...))) = 0.73908513321516064165531208767387... Any thoughts/explanations/exact solution etc? Thanks.
12. ### Volumes of Revolution

What is the volume of the figure bounded by y = 2x - x^2, y = 2x, x = 2, and rotated about the line y = -1. Is this the correct integral? $V = \pi \int_0^2 {((2x + 1)^2 - (2x - x^2 + 1)^2 } )dx$ Thank you for your time.
13. ### Hyperbolic Trig Inverses

I need to determine an algebraic form for arcsech(x) = ? So far what I've come up with is as follows: \L\ \begin{array}{l} y = \frac{2}{{e^x + e^{ - x} }} \\ y = \frac{2}{{e^x + e^{ - x} }}\left( {\frac{{e^x }}{{e^x }}} \right) \\ y = \frac{{2e^x }}{{e^{2x} + 1}} \\ ye^{2x} -...
14. ### Conservation of Mechanical Energy

A small car has an initial speed of 4.0m/s just before it enters a loop. What is the largest value for r (radius) that the loop can have if the car is to remain in contact with the circular track at all times? Answer: r = 0.327m What I tried was; before the car enters the loop it posses pure...