# Posts by David

Total # Posts: 2,277

CHEM
if something has a pH of 3.72 its not a base... did you mean pOH?

physics
T is period so you have frequency and period backwards

physics
use the formula T = 2*pi*sqrt(L/g) make sure you use SI units.

physics
Use the relationships 1 watt = 1 Joule / second E = mc^2 E = energy, m = mass, c = speed of light (3*10^8 m/s)

physics
you need to know that relationship that in that form, w = 2*pi*frequency thus w = 2*pi*525 2)cycles per 1 minute = 60 seconds *frequency = 60 * 535

math
13*3=39

math
6*10 + 10*(1/2) = 65

trig
Cosine is 0 at pi/2 3pi/4*t=pi/2 t=2/3

physics
w = 2*pi*period

physics
nevermind I thought it said that it began at its highest point. Since they didn't specify any initial conditions you're free to use either sin or cosine with no phase shift.

physics
It doesn't make a difference as long as your value for when t = 0 is correct since sin is just cosine phase shifted by pi/2. Cosine is probably easier in this case because then you wont need to do a shift.

physics
Period = time per cycle = 15 seconds frequency = 1 / period = 1/15 hz amplitude= 3 ft because its actually the distance from the center to each side. from there just put it into standard form.

Chemistry
It depends on the indicator. At the equivalence point, hypothetically they are equal. Most indicators however do not change color at exactly 7 and thus pH of the endpoint determines the concentrations of H+ and OH-

Physics
If the bus is moving with constant velocity, there's no net force on the bus, and thus you don't need to compensate for the bus's motion. If the bus is moving forward with constant acceleration, there will be a force pushing the bus forward, however from inertia ...

math
total time = 4 hours + 3 hours = 7 hours. Avg speed = total distance / total time Avg speed = 40 * 2 / 7 = 80/7 km/h

math
total distance = 526 + 5 * 70 avg speed = total distance / 12 min

science
Pv=nRT for both the initial and final state. Only thing your changing are temperature and since moles, R and volume are constant pressure must change. Thus P1/T1=P2/T2 P2=P1*T2/T1

Calculus
Volume=s^2*h=32 Surface area = s^2 + 4*s*h using volume equation, h=32/s^2 SA= s^2 + 4*s*(32/s^2) = s^2 + 128/s Take derivative dSA/ds and set equal to zero. 2s - 128/s^2 = 0 s^3 = 64 s = 4

Economics
D Rule 1 of microeconomics The optimal quantity for essentially everything is where marginal revenue = marginal cost

Physics
sum of forces vertical = 0 = mg - Ncos@ sum of forces horizontal = mv^2/r = Nsin@

math
to divide by a polynomial with power other than 1 you have to use long divison. However for this problem that's not necessary... just factor G(x) = (x-2)(x-3)/(x-3)(x+3) thus your only zero is x = 2 since the function is not defined at x = 3

Chemistry
Explain why the absolute values of the standard enthalpy change in the reaction and heat measured by the calorimeter are not equal. Assume that there are no measurement errors of any kind. In the previous problem I solved that Delta H rxn was -1500 and q = 1.519 x 10^6 J and I...

Chemistry
For the following reaction, the equilibrium constant Kc = 97.0 at 900K. If the initial concentrations of NH3 and H2S are both 0.20 M, what is the equilibrium concentration of H2S? H2S(g) + NH3(g) = NH4HS(s) Would you have to create an ICE chart for this type of problem?

Chemistry
The equilibrium constant Kp for the following reaction is 4 atm^2 at 300 K. AB(s) = A(g) + B(g) What is the equilibrium pressure of A(g) and B(g) above AB(s) at 300K? What is Kc at 300K? How would i solve this when they don't even give me any partial pressures?! All of the...

Chemistry
oh wow........ :[ thanks Dr. Bob

Chemistry
Which of the following statements are incorrect? 1) Gases are not included in the equilibrium constant expression. 2) Equilibrium constant can be increased by adding a catalyst 3) Large equilibrium constant favors reactants 4) Equilibrium is typically achieved in a very short ...

algebra
describe the number tha make the statement true: 3-16>23

Chemistry
The equilibrium constant Kc for the following reaction is equal to 0.20 at 250°C. Calculate the equilibrium constant Kp for the reverse reaction at the same temperature. COCl2 (g) = CO (g) + Cl2 (g) I'm sorry.. English is a second language for me. After solving for K&#...

english
Identify the capitalized part of speech in the following sentence: You should be proud of him, FOR he's a "jolly good fellow." Answer a. noun b. pronoun c. verb d. adjective e. adverb f. preposition g. conjunction .

physics
A simple pendulum has a mass m and carries a charge q. The pendulum is suspended between the vertical plates of a capacitor of separation distance d. If the string of the pendulum makes an angle θ with the vertical, what is the potential difference between the plates

physics
A simple pendulum has a mass m and carries a charge q. The pendulum is suspended between the vertical plates of a capacitor of separation distance d. If the string of the pendulum makes an angle θ with the vertical, what is the potential difference between the plates

math
Having difficulty with the four frequency ,to use in a table and determine and find the range ..im not understanding whays needed ?

physics
A simple pendulum has a mass m and carries a charge q. The pendulum is suspended between the vertical plates of a capacitor of separation distance d. If the string of the pendulum makes an angle θ with the vertical, what is the potential difference between the plates

english
Identify the subjects of the following sentences. Jacob's favorite poker game is Texas Hold'em

Art
What are the six architectural features of the Chartres Cathedral?

Chemistry
why does the equil end up being 0.8-x instead of 0.8 - 2x? and i solved for x but it gave me 2 different answers did I do something wrong?

Chemistry
the extra NO being added threw me off.. or is it supposed to be like Kc = 0.800M^2/[0.100M][0.100M] = 64 M?

Chemistry
At equilibrium, the concentrations in this system were found to be [N2] = [O2] = 0.100 M and [NO] = 0.500 M. N2(g) + O2(g) <-> 2NO(g) If more NO is added, bringing its concentration to 0.800 M, what will the final concentration of NO be after equilibrium is re-...

Calculus implicit
4sin(x-y)*d(x-y)=3y' + 3ycosx On the left I applied the chain rule, and on the right i used the product rule. 4sin(x-y)*(1-y')=3y' + 3ycosx Differentiate x - y and get 1 - y' Then do algebra to solve for y' 4sin(x-y) - y'*4sin(x-y) = 3y' + 3ycosx 3y...

physics
At the top of the loop mv^2/R=mg+N However if we ant minimum speed put N to zero. Thus to stay in the loop mv^2/R=mg v at the top thus = sqrt(g/R) To get to the top of the loop you are at a height of 2R, so the amount of energy lost getting there is 2mgR. Thus the initial ...

physics
I'm going to assume the diagram gives the tension in the string, because with what you stated you're missing a degree of freedom. Only two equations can be developed (Sum of forces = 0 in both the x and y direction). However, we're missing the tension's ...

chemistry
pH = -log[H+] = -log(.0019) Since HNO3 breaks into H+ and NO3- with a 1:1 ratio. Also log is base 10.

Elementary statistics
The total number of outcomes is 9C3, because there are nine apples and you are choosing 3 where order doesn't matter. P(0) = 5C3 / 9C3 because there are 5 good apples and you need to choose 3. P(1) = 5C2*4C1 / 9C3 P(2) = 5C1*4C2 / 9C3 P(3) = 5C0*4C3 / 9C3

Calculus-derivatives
Set the derivative equal to zero.

physics
Use the kinematic equation V = V0 + at defining up as positive. Thus, t = (V-V0)/a V0 is given as 100 m/s At the top of the path V = 0 a = -9.81 m/s^2 (gravity) Thus, t is about 10 seconds

math
27+6=33 need to regroup Yes or no

college algebra
a) x will be the width of the rectangle, and y will be the height. A = x*y = x(-1/2x+4) b) plug in x = 1, 2... 7 c) [0,8] because that's where the function crosses the x and y axis

college algebra
you have two points (32000,98000) and (35000,117500) Find the slope (117500-98000)/(35000-32000) put into point slope form y-y0=m(x-x0) using one of the two points for x0 and y0. b) Plug in x as 50,000 and solve for y. c) plug in y as 0 and solve for x

math
There are two poles. One is 60 feet tall and the other is 8 feet tall. they are 60 feet apart. How much wire would you need to connect the two poles?

Math
This question is from my workbook (Pre-Calculus 11). Can someone please help me understand it? Suppose theta is an angle in standard position with terminal army in quadrant III and tan theta = 6/3. Determine the exact calues of the other two primary trigonometric rations. In ...

Chemistry
Given that the vapor pressure of water is 17.54 torr at 20 C, calculate the vapor-pressure lowering of aqueous solutions that are 2.40 m in (a) sucrose, C12H22O11, and (b) aluminum chloride. Assume 100% dissociation for electrolytes. Sucrose Delta P = __ torr Aluminum Chloride...

Chemistry
Thanks guys!

Chemistry
at 25C and 795 torr, carbon dioxide has a solubility of 0.0356 M in water. What is the solubility at 25 C and 2070 torr? ____ M I know that at a given temperature, the solubility of a gas in a liquid is directly proportional to its pressure but how would that be set up in an ...

Chemistry
got it thank you to anyone who may have given thought!

Chemistry
Can someone confirm that I'd be doing this right? If an 0.520 m aqueous solution freezes at -3.00 C, what is the van't Hoff factor, i, of the solute? It says I can find the Kf values on a table. I had no idea which Kf value to use... so i just used water... is that ...

English
Anne Frank: The Diary of a Young Girl Briefly explain Anne’s relationship with her parents. How is her relationship with her father different from her relationship with her mother? What does each relationship tell you about Anne, her values, and her needs?

Chemistry
your approximations are very accurate.. thanks!

Chemistry
2C6H6(l) + 15O2(g) -> 12CO2(g) + 6H2O(l) + 6542 kJ If the heat from burning 7.000 g of C6H6 is added to 5691 g of water at 21 degrees C what is the final temperature of the water?

science
explain the topic heredity mystery.answers

chemistry
moles

chemistry
1000 grams is 6.261740764

chemistry
delta H is 21 kj sorry

chemistry
how much energy is required to convert 1.00 kg of iron III to atomic iron? Equation: Fe2O3 + 3CO ---> 2 Fe +3 CO2 delta H is 131kJ

math
my tank is 38 inches tall 45 inches in diameter. How many gallions does it hold?

physics
A uniform electric field of magnitude 2.80×104 makes an angle of 37 with a plane surface of area 1.60×10−2 .What is the electric flux through this surface?

macroeconmoics
983.58

physics
From the Eqn of motion we have: v=u+at =25+35*6 =360m/s recall that angacceleration=v^2/r r=40m, =360^2*40 =3240m/s^2

math
Write the following in terms of sin(θ) and cos(θ); then simplify if possible. sec(θ) / tan(θ) =

physics
A(n) 3.91 kg sphere makes a perfectly inelastic collision with a second sphere that is initially at rest. The composite system moves with a speed equal to one-third the original speed of the 3.91 kg sphere. What is the mass of the second sphere? Answer in units of kg

personal finances
Jenny intends to retire in 20 years. Upon retirement, she will require a yearly cash flow of \$80,000 for 25 years to support her lifestyle (yearly cash flows assumed to occur at the end of each year). Anticipating her retirement plan, she started investing \$6,000 per year five...

personal finance
Jenny intends to retire in 20 years. Upon retirement, she will require a yearly cash flow of \$80,000 for 25 years to support her lifestyle (yearly cash flows assumed to occur at the end of each year). Anticipating her retirement plan, she started investing \$6,000 per year five...

Chemistry
Here is the picture I am given: h ttp://imageshack.us/photo/my-images/209/diatomics.png/ This is supposed to be at a constant temperature, the hint says it's endothermic because energy is used to break the bonds. I believe it is a constant volume so w = 0 since it's ...

Chemistry
A sample of carbon monoxide gas whose mass is 6.37 g is heated from 25 oC to 192 oC at a constant pressure of 4.12 bar. Calculate q (in J) for this process. I got an answer of ~1110J Calculate w (in J) for this process. I am unsure how to calculate work considering there is no...

Chemistry
Okay, so I got: DHrxn = 8(395.5)+10(-241.83)-[2(-127.7)+13(o) =-5326.9 kJ mass(moles) ice x heat fusion 4.718mol(85/18.016)*6.01KJ/mol? =28.355Kj Then I have 4.718mol *75.291J/mol/oC x 100= 35522.2938J so sum together= 28.355kJ + 35.522 = 63.877kJ then 2(58) x (63.877/-53269kJ...

Chemistry
How many grams of butane must be burned to provide the heat needed to melt a 85.0-g piece of ice (at its melting point) and bring the resulting water to a boil (with no vapourization)? Assume a constant pressure of 1 bar and use the following data: Hfo(H2O(g))=-241.83 kJ/mol, ...

Chemistry
Suppose you wanted to heat a mug of water (250 mL) from room temperature 25 C to 100 C to make a cup of tea. How much energy (in units of calories and joules) would you need from your microwave?

chemistry
If 50.0 g of Ba(CN)2 reacts to produce 12.9 g of HCN, what is the percent yield?

math
wats 460 miles and 20 gallons as a unit rate

Mathematics
Find a fraction which reduces to 3/4 when the numerator and denominator are each decreased by 1, and which reduces to 4/5 when the numerator and denominator are each increased by 1.

Mathematics
Find a fraction which reduces to 3/4 when the numerator and denominator are each decreased by 1, and which reduces to 4/5 when the numerator and denominator are each increased by 1.

Chemistry
CH4 + 2O2 -> CO2 + 2H2O When 70 grams of oxygen react with methane, how many liters of CO2 gas are produced?

PARALLELOGRAM WRITING A PROOF
Qaud KATE has vertices K(-2,1) A(0,5) T(6,7) E(4,3). Prove that KATE is a parallelogram.

English
What does the poem "America" by Maya Angelou really mean.? What is really try to say in this poem..???

English
well that's that kind of the problem because i seem to find no differences, to me they seem pretty much alike.!

English
what are some differences of the work of Walt whitman " I hear america singing" & Woody Guthrie " This land is your land"..?

English
Thank you!(:

English
wat does the song "This land is your land" by Woody Guthrie actually mean.? What is the significance of the song?

English
how can you compare and contrast Walt Whitman "I Hear America Singing" to John Mellencamp "Little Pink Houses".??

English
Thank you so much for the help, now i have a good idea of what to do now!

English
how can you compare and contrast Walt Whitman "I Hear America Singing" to John Mellencamp "Little Pink Houses".??

Social studies
What is an example of checks and balances

Physics
Is the maximum torque that a given force can exert on an object occurs when the force is applied to the axis of rotation. I think it is true because torque is always specific when it comes to the axis of rotation. Am I correct?

Physics
I would say it is true that the center of mass of an isolated system moves at a constant velocity, as long as there is a constant force applied to it. Am I correct?

geometry/calculus
Use Cavalieri's Principle to find the area of the region. In the example we see a "leaning tower" with base 'a' and height 'b'. The left side of the leaning rectangle is given by y = x^2, the right side given by y = (x - a)^2 the answer to this ...

Physics
True or False: If a sphere of mass M and radius R and a cylinder of mass M and radius R start rolling down a ramp from the same location at the same time, they both reach the bottom of the ramp at the same time.

Physics
True or False: If a cannon fires a cannonball in an easterly direction, the tendency of the cannon to move to the west is a result of the principle of conservation of energy.

Physics
True or False: If no friction forces are present the work done by a force on an object increases either its kinetic energy or its potential energy.

math-probability
betsy goes running 2 days out of 7 and james goes running 5 days out of 7. What is the probability that one of them is running on any given day.

geometry
A farmer has 30yd of fencing and wants to enclose an area beside his barn. What are the dimensions of the region of maximal area, and what is that maximal area if the region is an is isosceles triangle with its base along side of the barn. Given -> legs of length 15, x = 1/...

physic
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