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# J

Questions103
• ### Find the volume of the solid (Cal2)?

Generated by revolving y=4-x^2 and y =0 about the line y=5.

My integral is ending up to be 2pi (56 - 18x^2 +x^4) dx , from x=0 to x = 2

• ### Linear Algebra Questions, HELP PLZ?

1) How many 3X2 matrices in rref are there? (3=row, 2 = column)

My Answer: I thought was 5 but did not have that option.

My 5th matrix was 0 1

0 0

0 0

2) For which value of K does the system of linear equations have infinitely many solutions?

x + y = 1

y - z = 3

x + z = k

I've worked this twice and still get 2.

I got these on a incorrect on a test and still confused.

Any helpful explanation much appreciated and MAX points to YOU

• ### Existence and Uniqueness theorem question?

for the DE: y' = x/(1 -y) , y(0)=1

does this satisfy the existence and uniqueness theorem?

Any help much appreciated

• ### Convert the following to a sine only function? HELP PLZ?

y(t) = 4sin(2pi t) + 15cos(2pi t)

This is what I did:

A_n = 15

B_n = 4

C_n = squareroot of the sum of the squares of A_n and B_n

Phase angle = arctan(15/4)

Result: 15.52sin(2pi t + 75.06)

Did I do this correct or do I have to find the offset (A_0)? I'm not really sure I'm a little unfamiliar with Fourier Series, but I have some calculus background. Any help in explaining is always appreciated/

• ### HELP!! with Raoult's Law and Vapor Pressure in Vapor Phase?

A solution is prepared by mixing .02 mol of CH2Cl2 and .08 mol CH2Br2 at 25C. Assuming the solution is ideal, calculate the mole fraction of CH2CL2 in the VAPOR phase.

VP pure CH2CL2 = 113torr

VP pure CH2Br2 = 11.4torr

I did this and got it correct, but I was not sure of wth i was doing. Can you help me in a step by step solution? I know the partial pressures, but I feel there is something I'm missing from actually knowing how to solve a problem like this. You don't have to solve the actual problem if you can tell/show me what are the relations involved so I can see if my thoughts were correct or not....thanks

• ### Work for point charges, I need help I forgot how to do these?

http://postimg.org/image/m5dwh3b0x/

See image for details of the drawing: How much work is required to assemble the four charges?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

(my wrong) solution: starting at the +3uC charge, it W=0, then to move the +16.8uC charge into position, costs k(+3uC)(+16.8uC)/13, then to move the -3uC charge into position, costs k(-3uC)(+16.8uC)/13m, then to move the -8.4uC charge into position costs,......I don't know what to do so I guessed the radius to be sqrt(507), but do I square the -8.4uC charge?

I'm not sure when to square the charge.

• ### HELP with GREEN'S THEOREM Problem. I don't get it!!?

http://postimg.org/image/3raek3r2f/

That 3pi, and 8 incase the image is fuzzy.

I tried and got -8pi, -16pi, and all other instances of craziness, all were wrong. Any help much appreciated or, if you can tell me how to fish this one out, is better thasn giving me the answer....

• ### Double Integral in Polar Coordinates set-up help!!?

T lies under the plane 3x - 4y + z = 12 and above the xy-plane, and inside the cylinder x^2 + y^2 = 2x.

This is how I set it up:

I found r to be 0 and 2cos

and I integrating over the plane? This is what is confusing.

I'm integrating the volume 12r - 3r^2cos -4r^2sin dr dtheta?

Is that correct? Any help much appreciated.

• ### Which is the weakest acid? Need help?

a) H2SeO4

b) H2SeO3

c) H2TeO4

d) H2TeO3

e) H2SO3

These are oxyacids, so, the more O attached the stronger they are. Also, The lower they are on the table, the stronger they are (or is that only true for binary acids?). This one is slightly confusing for me, because I don't know how to analyze them.

As always, your help and insight is always much appreciated.

• ### Which of the following salt sol'n has the highest pH?

a) 0.10 M NaIO2

b) 0.10 M NaClO2

c) 0.10 M NaClO

d) 0.10 M NaIO

e) 0.10 M NaIO3

I said d), this is why: this question is asking for highest pH, thus strongest acid, I'm given bases. So I have to look for the weakest base here. I can eliminate a), b), and e) because they have more O attached and will be very strong bases (is that the right reason?). also, the last two will form HClO and HIO in water. Now I have to see which one is strongest acid. I guessed on this and said it was HIO b/c I is lower down than Cl, but I'm not sure if I did the whole reasoning right. Any help is much appreciated. I think I'm getting mixed up with binary and oxyacids.

• ### Why is HS^- a stronger base than HSe^-?

I guessed this on a question and got it right, but don't understand why it really is. I figured that since the S is more electronegative than Se, it will want to snatch more H^+ than Se?

Is that right and is there some more better way to think of it?

Thanks, and your help is always much appreciated.

• ### pH of HCl in solution?

What is the pH of a solution in which 298mL of HCl(g), measured at 26.3 C and 1.02 atm, is dissolved in 1.5 L of aqueous solution?

• ### Lagrange Multiplier PRoblem?

Given f(x,y) = 128x + 144y and 64x^2 + 288y^2 = 9216

Find extrema if it exists.

Ok, after partial differentiation and solving for lambda, I got x = 4y

I then solved y^2 = 288/41 and x^2 for 4608/41

But my answer is 11247223/6469, and they they it is wrong? Can you work the problem and see if you get the same answer?

• ### Position of Boat A and Boat B. Partial Derivative Problem?

The position of boat A at time t is given by the parametric equations

x1 = −5t, y1 = 5t

and the position of boat B at time t is given by

x2 = 5t, y2 = 2t + t2

where 0 < t < 15, and

x1, y1, x2, y2

are measured in feet and t is measured in seconds. How fast is the distance between the two boats changing when t = 10? (Round your answer to the nearest whole number.)

I remember solving problems like this in related rates in cal 2, however, that was over a year ago and I never really understood them. Any help much appreciated.

• ### Partial Derivatives question for a system?

Given the system:

x = 9/2(u^2 - v^2)

y = 2uv

find partials, du/dx, du/dy, dv/dx, dv/dy

• ### Another Differentials Question?

The specific gravity of an object with density greater than that of water can be determined by using the formula

S= A/(A-W)

where A and W are the weights of the object in air and in water, respectively. If the measurements of an object are

A = 3.9 lb

and

W = 3.5 lb

with maximum errors of 0.02 lb and 0.04 lb, respectively, find the approximate maximum error in calculating S.

My wrong solution:

Ok, dA= .02 and dW = .04

The partials I got were:

[-W/(A-W)^2 * dA] + [ A/(A-W)^2 * dW] = dS

After plugging in, I got the error to be .5375

But that answer was incorrect. Anyone can see where I went wrong? Thanks,

• ### use implicit differentiation to find Partial (dz/dx) and (dz/dy)?

sin(xyz)=x+3y+3z

partial (dz/dx) holding y constant:

1. y(xz)' cos(xyz)= 1 + 3*(dz/dx)

2. y(z + x*dz/dx)cos(xyz)= 1 + 3*(dx/dx)

now what???

• ### Find the fist partial derivatives of the function f(x,y)?

f(x,y) = from y to x, of integral cos(t^9) dt

So, I'm assuming I integrate using IBPs and then find the first partial derivatives f_x and f_y?

Not sure,

Thanks,

• ### What is the order of the reaction?

I'm given this table:

When .15M, rate is .021M/s

When .30M, rate is .164M/s

When .60M, rate is 1.315M/s

This is what I did:

I looked at first and last values. I came up with 2 = 8^x; thus obviously x = 1/3. When I entered this into the system it said that answer was wrong. The actual answer was 3. What's the deal. I did it exactly like how the book said. Any one can explain?

Thanks,