Friday

September 19, 2014

September 19, 2014

Total # Posts: 823

**math**

Average Growth Rate(2000-2009)of China - GDP: 10.9 Population: 0.8 Per Capita GDP: 10.1 Ethiopia - GDP: 7.5 Population: 2.8 Per Capita GDP: 4.7 How fast does total output(GDP)have to grow in order to raise per capita GDP in Instructions: Enter your responses to one decimal ...
*October 3, 2012*

**English **

What are the nouns and verbs in the sentence. Life is full of choices, so I must learn to make good ones.
*September 27, 2012*

**Biochemistry**

Acetylcholinesterase catalyzes the hydrolysis of the neurotransmitter acetylcholine: Acetylcholine + H2O actetate + choline The KM of acetylcholinesterase for its substrate acetylcholine is 9 x 10-5 M. In a reaction mixture containing 5 nanomoles/ml of ...
*September 22, 2012*

**Linear Algebra**

awesome, thanks a lot Steve, that link will come in handy!
*September 21, 2012*

**Linear Algebra**

Solve the following system using Gauss's algorithm (a) x1 + 2x2 + 4x3 + 6x4 = 3 2x1 + x2 + 3x3 = -6 -2x1 + x2 + 6x3 + 4x4 = -11 2x1 + x2 + x3 = 0 so the matrix will be: 1 2 4 6 3 2 1 3 0 -6 -2 1 6 4 -11 2 1 1 0 0
*September 21, 2012*

**Math**

Staring from the pit, Helen made three laps around a circular track at 40 seconds per lap. She than made a 30-second pit stop and two and a half laps before running off the track and getting stuck in the mud for the remainder of the race. Graph Helen's distance from the ...
*September 18, 2012*

**Calculus**

Calculate the following integral and determine whether it's convergent, or divergent. integral at [-3,0] x dx / sqr(9 - x^2)
*September 15, 2012*

**calculus**

Thanks Reiny and Steve. Now to pass the exam!
*September 14, 2012*

**calculus**

Calculate the following integral: ∫ dx / x(1 - √x)^2
*September 14, 2012*

**Calculus**

thanks Steve! You're a lifesaver
*September 13, 2012*

**Calculus**

Calculate the following integral: ∫ sec^4 (3x)/ tan^3 (3x) dx For this one, can I bring up the tan to tan^-3?
*September 13, 2012*

**Algebra**

Algebra Question: A team wins 15 of their first 20 games. If they win only half the time from now on, how many games will they have to play in order to win 60% of their total games? I have it figured out manually, but cant get it in equation form.
*September 12, 2012*

**Calculus - Question**

If I go with my first assumption I get this: ∫ sec^4 (3x) tan^-3 (3x) = ∫ sec^3 (3x) tan^-4 (3x) sec(3x)tan(3x) dx = ∫ sec^3 (3x) (sec^-4 3x - 1)sec(3x)tan(3x) dx u = sec(3x) dx du = 3sec(3x)tan(3x) dx > 1/3du = 1/3 ∫ u^3 (u^-4 - 1) du = 1/3 ∫...
*September 12, 2012*

**Calculus - Question**

Or do I use the rule of ∫ sec^n x dx divided by the rule of ∫ tan^n x dx?
*September 12, 2012*

**Calculus - Question**

Am I allowed to do this? for the integral of ∫ sec^4 (3x)/ tan^3 (3x) dx I change it to ∫ sec^4 (3x) tan^-3 (3x) From here I use the rule for trigonometry functions.
*September 12, 2012*

**Linear Algebra**

Last number from the sample test! A plane P passes by the coordinates: A(1,0,-7); B(-2,-1,0); C(0,0,-3) Using the equation of the line D: x= 7+12t, y= -1-6t, z= 2-2t, Find the equation of a line that's entirely part of the plane P and that is perpendicular to the line D at...
*September 10, 2012*

**Linear Algebra 2**

This is another question I can't figure out. Given planes pie1 and pie2 defined as: pie1: 2x + 5y - 7x + 2 = 0 pie2: x + y - z + 3 = 0 (b) Give the equation of the line of intersection of these two planes. I only found the answer for (a) where they ask to find the angle ...
*September 9, 2012*

**Linear Algebra**

THanks again Mate! You've been a big help lately, I really appreciate it.
*September 9, 2012*

**Linear Algebra**

So I'm studying for my first exam and I'm stuck on this number. Given both lines: D1: (x,y,z) = (2,0,0) + k(0,3,0) D2: (x,y,z) = (2,0,2) + k(0,0,1) (a) Give the algebraic equation of the plane containing both lines. I know that I have to start off by finding the ...
*September 9, 2012*

**Linear Algebra**

THanks Mate!
*September 8, 2012*

**Linear Algebra**

2 people move in the same direction along a line of equation: (x + 3)/10 = (y + 10)/20 = (z - 10)/-20 Mobile M1 is at a point A(-3, -10, 10) and moves at a velocity of 6m/s towards point B(7, 10, -10) where Mobile 2 is found, walking in the same direction at a velocity of 3m/s...
*September 8, 2012*

**Calculus**

THanks Steve and Reiny!
*September 7, 2012*

**Calculus**

Hello, I just wanted to verify if my work was good. Calculate the following integral by parts: ∫ upper limit is 1/5 and lower limit is 1/10. of 10sin^-1 (5x)dx so first I named the variables: u = 10 sin^-1 (5x) du = 50 / sqr(1-25x^2) dv = dx v = x so we get: = 10 sin^-1...
*September 7, 2012*

**Definite integral by parts (correction)**

Hello, I just wanted to verify if my work was good. Calculate the following integral by parts: ∫ upper limit is 1/5 and lower limit is 1/10. of 10sin^-1 (5x)dx so first I named the variables: u = 10 sin^-1 (5x) du = 50 / sqr(1-25x^2) dv = dx v = x so we get: = 10 sin^-1...
*September 5, 2012*

**Math**

Knowing u = (4,0,-3), v = (x,3,2) and that the orthogonal projection of v on u is a vector of norm 6, determine x. Thank you
*August 27, 2012*

**Linear Algebra**

Ok this is the last one I promise! It's from a sample exam and I'm practicing for my finals :) Verify if the following 4 points are consecutive vertices of a parallelogram: A(1,-1,1); B(3,0,2);C(2,3,4);D(0,2,3) (b) Find an orthogonal vector to the plane containing the ...
*August 27, 2012*

**Linear Algebra 2 question**

sorry I wrote D, but there is no D, just AB and C
*August 26, 2012*

**Linear Algebra 2 question**

Hello, I have another question from my linear algebra class. I'm asked to find the area of a triangle using determinants, but they don't give me the vertices, only the sides. Where A,B,C and D are the vertices, u and v are 2 out of the 3 sides. Now they give me u=(-3,1...
*August 26, 2012*

**Linear Algebra**

Knowing u = (4,0,-3), v = (x,3,2) and that the orthogonal projection of v on u is a vector of norm 6, determine x. Thank you
*August 26, 2012*

**science**

1.How many meters away is a cliff if heard one half second after the original sound? Assume that sound travels at 343m/s on that day
*August 21, 2012*

**Physics - Electromagnetism 2**

Two coils, held in fixed positions, have a mutual inductance of 165 µH. What is the peak emf in one coil when the current in the other coil is I(t) = 16.0 sin(1.15 103t), where I is in amperes and t is in seconds? Just a few hints on how to start it off would be very ...
*August 16, 2012*

**Physics - Electromagnetism**

An inductor in the form of a solenoid contains 440 turns and is 15.8 cm in length. A uniform rate of decrease of current through the inductor of 0.421 A/s induces an emf of 175 µV. What is the radius of the solenoid?
*August 16, 2012*

**Physics 2**

thanks. It's all good, I understand your approach and I really appreciate it!
*August 14, 2012*

**Physics 2**

thank you very much drwls, this is a question from a sample exam, getting ready for my finals tomorrow!
*August 14, 2012*

**Physics 2**

the character that doesn't show up is the emf (E)
*August 14, 2012*

**Physics 2**

Show that during the charging of the capacitor in an RC circuit, the charge of the capacitor, as a function of time, is: q(t) = C(1 – e-t/RC)
*August 14, 2012*

**Physics - Electromagnetism**

A charge +q is at the origin. A charge –2q is at x = 2.00 m on the x axis. For what finite value(s) of x is (a) the electric field zero? (b) the electric potential zero?
*August 14, 2012*

**enviroment**

The surroundings or conditions in which a person, animal, or plant lives or operates.
*August 13, 2012*

**Physics - Electromagnetism**

A square loop (length along one side = 20 cm) rotates in a constant magnetic field which has a magnitude of 2.0 T. At an instant when the angle between the field and the normal to the plane of the loop is equal to 20 and increasing at the rate of 10/s, what is ...
*August 12, 2012*

**Physics - Verification**

Two long straight parallel wires separated by a distance of 20 cm carry currents of 30 A and 40 A in opposite directions. What is the magnitude of the resulting magnetic field at a point that is 15 cm from the wire carrying the 30-A current and 25 cm from the other wire? So I ...
*August 12, 2012*

**Life Science**

10 Microsporidia Chytridiomycota Neocallimastigomycota Blastocladiomycota Zoopagomycotina Kickxellomycotina Entomophthoromycotina Mucoromycotina Glomeromycota Dikarya
*August 12, 2012*

**math**

61-43 (Goal % and current %) = 18 % 18% / 0.6% = 30 years
*August 12, 2012*

**Art Appreciation**

Discuss how art was used as a vehicle for propaganda, and whether such use is present in the works of Höch, Grosz, and Picasso. Use one example from Gardner's Art through the Ages and one from the Internet.
*August 9, 2012*

**Calculus - Riemann Sum**

Given a function f(x) = squr(3 + 2x), on [-1,1], subdivided into 4 equally large intervals, calculate the Riemann sum SR4 = 4Ei=1 f(xi)delta(x). my attempt at the solution: [-1,1], a = -1 and b = 1 delta(x) = 1 - (-1)/n = 2/n xi = a + delta(x)i xi = -1 + 2/n(i) so after adding...
*August 6, 2012*

**Math**

so for (a) you used Y = Yo + Vot+ 1/2at^2 so when you derive it, you get time for the other ones, got it. THanks a lot Reiny
*August 6, 2012*

**Calculus**

oops, that was under my brother's name hehe
*August 6, 2012*

**Calculus**

Solve the differential equation dy/dx = -xe^y and determine the equation of the curve through P(1,2) I tried solving the differential equation and I get y = log(x^2/2 + C). Is this correct? Now I forgot how to find the equation. Thank you!
*August 6, 2012*

**Chemistry 2**

oh okay, well in that case there's no change? Nothing happens to the ethanol and we get the same K constant that we had previously?
*August 3, 2012*

**Chemistry 2**

oh this is just a theoretical question. It's about the hydrolysis of ethyl acetate, it gives ethanol and acetic acid as the products
*August 3, 2012*

**Chemistry 2**

Supposed you stoppered the flasks after your titration to determine the equilibrium constant and kept the solutions for another day so that the equilibrium was re-established. What would happen to the amount of ethanol present? What would be the relationship of the original ...
*August 3, 2012*

**Chemistry**

okay thanks Dr.Bob, that's exactly what I did too.
*August 3, 2012*

**Chemistry**

because it's a 1:1 ratio for all, then at rxn, we would have -x for both EtAc and H2O and + x on the right, so x = 0.03045. Is this correct?
*August 3, 2012*

**Chemistry**

does it mean that because acetic acid has 0.03045 mol at equilibrium that x = 0.03045 mol? So then Ethanol would also have 0.03045 mol at eq and EtAc and H20 would both be their initial [conc] - x?
*August 3, 2012*

**Chemistry**

Find the equilibrium moles for the following reaction with initially 0.051 mol for Ethyl acetate, 0.260 mol for water and 0.03045 mol of acetic acid at equilibrium. I'm not sure how to get the ones at equilibrium for the left side or even how much you have to take away for...
*August 3, 2012*

**CHemistry- For Dr.Bob**

Awesome, it's all clear now, thanks a lot again!
*August 2, 2012*

**CHemistry- For Dr.Bob**

Yes I see my mistake now, because they first ask to find the moles of NaOH used, so would it simply be 0.015 mol? If I remember you had a density of HCl solution and the mass of that solution was mass = volume x density = 5 mL x density in g/mL = ? g. You can estimate the mass...
*August 2, 2012*

**CHemistry- For Dr.Bob**

Hey Dr.Bob, I asked two days ago a question about a titration lab I had that you answered, but I still have one more question about that lab. Here's the lab summary: For my chemistry of solutions class, we had a titration lab where we titrated NaOH into an HCl + H2O mix. ...
*August 2, 2012*

**Chemistry - titration lab**

Amazing, thank you DrBob!
*July 31, 2012*

**math**

Which number property shows that the two sides of the equation are equal? 841 + 841(37) + 841(623) = 841 + 841(37 + 623)
*July 29, 2012*

**Physics - Electromagnetism**

thank you Elena!
*July 25, 2012*

**Physics - Electromagnetism**

This is the last question for a final exam preparation sheet and I can't figure out the answer. Any help would be greatly appreciated. Thank you. - One very long wire carries current 10.0 A to the left along the x axis. A second very long wire carries current 75.0 A to the...
*July 25, 2012*

**Chemistry**

I had an equilibrium laboratory and had to answer a few questions after the lab. Here are 2 questions I can't seem to know how to answer. 1. Explain in your own words why a saturated solution in contact with some undissolved solid is considered to be an equilibrium ...
*July 19, 2012*

**Art Appreciation**

Explain how Florence reflects the ideals of the dominant city-state and how some of the geographical, economical, social, and artistic forces shape this ideal. Use one example from Gardner’s Art through the Ages and one example from the Internet.
*July 14, 2012*

**Chemistry**

Is ClO2>- a Bronsted acid, base, or both?
*July 9, 2012*

**Chemistry - Correction**

Thanks Bob!
*July 3, 2012*

**Chemistry - Correction**

I just wanted to be sure if my answers make any sense. Thank you; For the reaction of ammonia: N2(g) + 3H2(g) --> 2NH3(g) suppose equilibrium has been established. Explain how and why the position of equilibrium will shift in response to the following changes: (a) ...
*July 3, 2012*

**Chemistry**

I just wanted to be sure if my answers make any sense. Thank you; For the reaction of ammonia: N2(g) + 3H2(g) --> 2NH3(g) suppose equilibrium has been established. Explain how and why the position of equilibrium will shift in response to the following changes: (a) ...
*July 2, 2012*

**Chemistry 2 **

Chlorine atoms contribute to the destruction of the earth's ozone layer by the following sequence of reactions: Cl + O3 --> ClO + O2 ClO + O --> Cl + O2 Where the O atoms in the second step come from the decomposition of ozone by sunlight: O3 --> O + O2 What is ...
*June 28, 2012*

**Chemistry**

Thank you Bob
*June 28, 2012*

**Chemistry**

Nitrogen Oxides, NOx (mixture of NO and NO2). The NOx in the atmosphere is slowly broken down to N2 and O2 in a first-order reaction. The average half-life of NOx in the smokestack emissions in a large city during daylight is 3.9 hours. (a) Starting with 1.50 mg in an ...
*June 28, 2012*

**physics**

a pneumatic nail gun with muzzle speed of 37m/s fires a 5.0cm nail directly into a hard wood that stops the nail just when it is full embedded in the wood. Assuming the nail's deceleration to be constant, what is its magnitude?
*June 6, 2012*

**Chemistry**

so I found out I need to extrapolate the temperature, but how do I do that, if I only have a graph and no other information
*May 30, 2012*

**Chemistry**

Plus, would that be the temperature I use in my calculations of Heat, or do I take the initial temperature of my column and the final one? I doubt it's this though
*May 30, 2012*

**Chemistry**

I had a lab about calorimetry where we would have a temperature probe in a calorimeter cup and then pour hot water into it to form a mixture until our graph (automatically plotted from the data that's recorded by the computer). Now for the report they ask us to draw a ...
*May 30, 2012*

**Chemistry**

I see, thanks a lot Bob!
*May 29, 2012*

**Chemistry**

Derive a formula for the molar mass of the solute in terms of the freezing point depression, deltaT, the freezing-point constant, Kf, and the masses of solvent, msolvent, and solute, msolute, used in an experiment like this one. SHow your work and include all unites in your ...
*May 29, 2012*

**Chemistry**

I get it now, thanks again Bob
*May 23, 2012*

**Chemistry**

Thanks Bob! As for deltaS, it just says Entropy increases in all spontaneous reactions, there's nothing more specified, so I assumed that it was deltaS and not deltaSuniverse
*May 23, 2012*

**Chemistry**

(b) deltaG < 0 , are product-favored and occur with rapid transformation of reactants to products. HOw is this incorrect? deltaG < 0 is product-favored and is rxn forward. Thank you
*May 23, 2012*

**Chemistry**

So when there's a spontaneous reaction, deltaS is > 0 , I confused that with increase. I still don't see how it's incorrect
*May 23, 2012*

**Chemistry**

Explain why each of the following is incorrect: (a) Entropy increases in all spontaneous reactions. Wouldn't (a) be actually correct? Because when there's a spontaneous reaction, you have less stable molecules and more disorder. It will be lower in some reactions than ...
*May 23, 2012*

**GEOMETRY**

Given that AB is a tangent of the circle with the center at X, AB = 12, and XD = 2.5, which is the length of DB?
*May 23, 2012*

**physics**

In one room the radiator has a dark color (emissitivity = 0.818). It has a temperature of 64.8 oC. The new owner of the house paints the radiator a lighter color (emissitivity = 0.417). Assuming that it emits the same radiant power as it did before being painted, what is the ...
*May 21, 2012*

**physics**

A cubical piece of heat-shield-tile from the space shuttle measures 0.18 m on a side and has a thermal conductivity of 0.065 J/(s·m·C°). The outer surface of the tile is heated to a temperature of 1050°C, while the inner surface is maintained at a ...
*May 21, 2012*

**E&M Physics**

this is the image ww w.ux1.eiu.edu/~cfadd/1360/24Gauss/24Hmwk/24.05. html
*May 18, 2012*

**E&M Physics**

Hello, I have this number where I don't understand why there's a negative sign to it. Consider a closed triangular box resting withing a horizontal electric field of magnitude E = 7.8 x 104 N/C as shown here. Calculate the electric flux through (a) the vertical surface...
*May 18, 2012*

**Chemistry**

I got it, oxidation state of reactants is going to be (+5) and products (-4) so it's an oxidation reaction, thanks for the info Bob!
*May 16, 2012*

**Chemistry**

so the oxygen molecule detachs from the Hydroxide and moves to electronegative species right?
*May 16, 2012*

**Chemistry**

Hello, I had a lab about calorimetry and one of the questions was if the reaction of acetone with hypochlorite is an oxidation/reduction or acid/base. Would the answer be: oxidation/reduction because the oxygen from the hydroxide from the Sodium hydroxide detaches and joins ...
*May 16, 2012*

**Ashford**

Employee motivation
*May 10, 2012*

**Chemistry**

thanks!
*May 9, 2012*

**Chemistry**

3) You pour 240 mL of Coke into a glass, where the T of the beverage is at 10.5 *C. You then add one ice cube of 45g. Determine the final temperature and the amount of ice remaining, if any. So I know that there won't be any more ice left because they will reach thermal ...
*May 9, 2012*

**physics**

A steel (Young's modulus 2.0 x 1011 N/m2) wire is strung between two supports attached to a ceiling. Initially, there is no tension in the wire when it is horizontal. A 88-N picture is then hung from the center of the wire, as the drawing illustrates, so the ends of the ...
*April 14, 2012*

**Chemistry please help**

How would an HA acid behave in water if it were a strong acid, weak acid, and non-electrolyte?
*March 31, 2012*

**Chemistry Help Please**

i do not understand how to solve this problem, please help 10.0mL 0.5M sulfuric acid can neutralize what volume of 0.5M ammonium hydroxide?
*March 31, 2012*

**calculus**

find the total differential of the function f(x,y)= xye^(x+y)
*March 30, 2012*

**calculus**

find the total differential of the function. f(x,y) = 5y/x-y
*March 30, 2012*

**statistics**

A Packaging Company sells soda and claims each can contains 12 oz. A random sample of 15 sodas yielded a sample mean of 11.2 oz. Given the sample standard deviation is 0.3 oz, estimate the margin of error for a 90% confidence interval.
*March 29, 2012*

**statistics**

A poll claims that 70% of the population is for a new amendment. A random sample of 49 people showed that 27 voted in favor of the new amendment. Give a 95% confidence interval. Give lower limit and upper limit accurate to four decimal places
*March 29, 2012*

**math**

If Pete colored 1/2 of a poster and Rebecca colored 1/3 of the poster. What fraction still needs to be colored?
*March 29, 2012*

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