Saturday

October 1, 2016
Total # Posts: 953

**History**

ccbdb

*October 17, 2012*

**Microeconomics - University of Boston**

4. If Cassandra bought 16 cotton blouses last year when her income was $40,000 and she buys 24 cotton blouses this year when her income is $50,000, then what is her income elasticity of demand? Interpret what the income elasticity of demand you just calculated means to you. ...

*October 17, 2012*

**Microeconomics**

4a. In the market for hand-made guitars, when the price of guitars is $800, annual revenues are $640,000. When the price falls to $700, annual revenues decline to $630,000. Over this range of guitar prices, is the demand for hand-made guitars elastic, unit-elastic, or ...

*October 17, 2012*

**Microeconomics**

The producer of X is contemplating a price change and has asked for your advice. After some empirical investigation, you conclude that the price elasticity of demand for X is 1.25. As an economist, what would you advise the producer to do in order to raise total revenue? Would...

*October 17, 2012*

**Physics**

In Case A the mass of each block is 4.8 kg. In Case B the mass of block 1 (the block behind) is 9.6 kg, and the mass of block 2 is 4.8 kg. No frictional force acts on block 1 in either Case A or Case B. However, a kinetic frictional force of 9.4 N does act on block 2 in both ...

*October 14, 2012*

**chemistry**

in an experiment, 2.50g of salicylic acid is reacted with 10.31g of methanol. the yield of methyl salicylate, C8H8O3, is 1.27g. what is the percentage yield?

*October 13, 2012*

**chemistry**

if a reaction vessel contains 11.5g NH3, 12.0g O2, and 10.5g CH4, what is the maximum mass in grams of hydrogen cyanide that could be made?

*October 13, 2012*

**chemistry**

in a reaction of 3Cu(s)+ 8HNO3(aq)¨ 3Cu(NO3)2(aq) +2NO(g) + 4H2O(l). if 5.58 grams of Cu(no3)2 is made how many grams of nitrogen monoxide is present

*October 12, 2012*

**chemistry**

copper metal reacts with nitric acid. assume that the reaction is 3Cu(s) + 8HNO3(aq) ——> 3Cu(NO3)2(aq) + 2NO(g) + 4H2O(l). if 5.58 grams of Cu(NO3)2 is obtained, how many grams of nitrogen monoxide would have formed

*October 12, 2012*

**Science**

In the early 20th century, some scientists were reluctant to accept the conclusion that DNA could be the genetic material because it is so_________________.

*October 9, 2012*

**IMPERIALISM AND THE PROGRESSIVE ERA**

Ivy L. Lee

*October 9, 2012*

**Biology**

A bacterium that synthesizes an enzyme that neutralizes an environment toxin would probably use a(n) _____________ operon to regulate production of the enzyme.

*October 9, 2012*

**world history**

you should email me, im also in Penn Foster lol we could cut work in half if we work on this crap together.. rvargas1020 @ live . com

*October 6, 2012*

**english 4**

Please explain to me how to determine the answer im looking for

*October 3, 2012*

**english 4**

if i knew i would not ask

*October 3, 2012*

**english 4**

The two waiters exchanged a look whose meaning was clear to me. what type of clause or phase is used?

*October 3, 2012*

**english4**

can you explain to me how to determine what type of verbal it is my choices are Participle, Gerund, and infinitive

*October 3, 2012*

**english4**

What do you think Ms. Sue

*October 3, 2012*

**english4**

Well as the verbal i chose "to be moved" im not sure what type of verbal it is!

*October 3, 2012*

**english4**

He will not allow the table to be moved. identify the Verbal in the sentence and type of verbal

*October 3, 2012*

**english4**

what type of clause or phrase is used in the sentence: we hit a snag while rowing to shore

*October 3, 2012*

**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*

**Physics**

Max Height = 1,306M Range = 3,840M Hangtime/Total Time = 32 seconds Time to reach max height = 16 seconds

*September 30, 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*