# Posts by David

Total # Posts: 2,271

**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**

23

**chemistry**

please, what is another name for double indicator titration and if the indicators are reversed is there any change in the result.

**math**

The ages of two children are 11 and 8years.In how many years time wil the product of their ages be 208

**physics**

if a tank was at 62 degrees farenhiet with a pressure of 14.7 psi. what would the presure be if the temperature rose to 178 degrees farenhiet?

**math**

X is a complex number. but X is not equal to 1. X^2011=1 Compute the sum X^(2n)/((x^n)-1) where n=1,2,3...2010

**physics**

Once a 28 kg crate is in motion on a horizontal ﬂoor, a horizontal force of 51 N keeps the crate moving with a constant velocity. The acceleration of gravity is 9.81 m/s. What is µk, the coeﬃcient of kinetic friction, between the crate and the ﬂoor

**Physics**

By what distance must two charges of +2 C and +10 C be separated so that the repulsive force between them is 3.70*10^10 N?