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September 20, 2014

Posts by Robert


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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