Wednesday

October 7, 2015
Total # Posts: 22,103

**math**

integral ln x / x = (1/2)(ln x)^2 because d/dx (ln x)^2 = 2 ln x (1/x) you can do the rest
*April 22, 2015*

**calculus**

x is + over the interval so the function we want to integrate is always + over the interval when you see something squared on the bottom think: d/du (v/u) = [ u dv/du - v ] / u^2 so here let u = (3x+1) if v were 1 d/du(v/u) = [0-3]/(3x+1)^2 so let v = -1/3 and integral = -(1/3...
*April 22, 2015*

**Physics**

Moments about center of yoyo shaft torque = 2*(.5/100) = .01 NM omega = alpha * t but alpha = Torque/ I so omega =Torque * t/I or I = Torque * t / omega = .01 * 5 / 15 ========================= angle = (1/2) alpha t^2 ============================ now for part c I assume you no...
*April 22, 2015*

**Math**

a ton is 2000 pounds in English as opposed to metric or shipping units. I suspect you want the 2000 pound ton then 7 tons is 14,000 pounds so 14,000 / 40 = 1400/4 =?
*April 22, 2015*

**Science**

The wiki article is pretty good on this subject: http://en.wikipedia.org/wiki/Thermocouple
*April 22, 2015*

**Math**

you are looking for the least common multiple of 252 and 408 The way I do such problems is to factor each 252 = 2*126 = 2*2*63 = 2*2*3*21 = 2*2*3*3*7 then 408 = 2*204 = 2*2*102 = 2*2*2*51 so we need 2*2*2 * 3*3 * 7 * 51 = 8*9*7*51=25704 check 25704 / 252 = 102 blue 25704 / 408...
*April 22, 2015*

**Math**

(Y2-Y1) / (X2-X1) for example (-2-4)/(2 - -1) = -6/3
*April 22, 2015*

**Chemistry**

Dr Bob told you much more precisely than I how do do this sort of problem. I suggest just doing them. by the way, your book or Google will tell you how many grams of any element are in a mol. for example for H about 1 for O about 16 for C about 12 etc Do you not have a ...
*April 22, 2015*

**If you answer these questions I will pass this cla**

I assume all problems are at STP where a mol of gas is 22.4 Liters
*April 22, 2015*

**If you answer these questions I will pass this cla**

Hint, convert grams to mols
*April 22, 2015*

**Trig**

yes, about 1.3 radians
*April 22, 2015*

**Trig**

I assume you mean y = 7 cos θ + 24 sin θ well, my inclination is to look for where the derivative is 0 dy/dθ = -7 sin θ + 24 cos θ = 0 or tan θ = 24/7 = 3.43 θ = 73.7 degrees
*April 22, 2015*

**AP Physics**

Steve tried to answer earlier but you have still not given direction of velocity vector of the first ball. Anyway as he said conserve momentum in the north direction and in the east direction.
*April 18, 2015*

**Physics**

hmmm, that flat earth assumption again ! 60 = (1/2)(9.81) t^2
*April 18, 2015*

**Vectors**

x = -2 + 2 s y = 3 + 3 s z = 1 - s on the y axis, x and z are 0 0 = -2 +2 s 0 = 1 - s so it is where s = 1 then y = 3+3 = 6 so (0 , 6 , 0 )
*April 18, 2015*

**Math - use flat earth**

earth flat at this range :)
*April 17, 2015*

**Vectors**

Beats me Ryan
*April 17, 2015*

**Vectors**

find slope of perpendicular original is slope = -1 so slope of perpendicular is -1/-1 = 1 pick a point on line 2, like (0,0) then equation of perpendicular through that point is y = x (just to make it east) where does y = x hit the first line? 2 x + 2 x = 16 x = 4 then y = 4 ...
*April 17, 2015*

**PRE - CALCULUS**

I do not have time NOTE in your previous question, the determinant of the 3 by 3 coef matric is zero, can not solve.
*April 17, 2015*

**DETERMINANT = 0**

calculate the determinant of the 3 by 3 on the left as if you were going to do Cramer rule THE DETERMINANT IS ZERO
*April 17, 2015*

**PRE - CALCULUS**

Huh, they are 4 -1 3 12 1 4 6 -32 5 3 9 20 the trouble is that it can not be solved
*April 17, 2015*

**PRE - CALCULUS**

You mean this ? 17y+21z = -140 that would be 0 17 21 -140
*April 17, 2015*

**PRE - CALCULUS**

You can not reduce the last row to 0 0 1 something
*April 17, 2015*

**PRE - CALCULUS**

1 4 6 -32 yes but your problem gives a very strange answer
*April 17, 2015*

**PRE - CALCULUS**

http://www.idomaths.com/gauss_jordan.php
*April 17, 2015*

**PRE - CALCULUS**

4 -1 3 12 1 4 6 -32 5 3 9 20 Step 1: Swap row 3 and 1 5 3 9 20 1 4 6 -32 4 -1 3 12 Step 2: Divide row 1 by 5 1 0.6 1.8 4 1 4 6 -32 4 -1 3 12 Step 3: Subtract row 1 from row 2 1 0.6 1.8 4 0 3.4 4.2 -36 4 -1 3 12 Step 4: Subtract (4 × row 1) from row 3 1 0.6 1.8 4 0 3.4 4...
*April 17, 2015*

**PRE - CALCULUS**

I think they gave you Sk k(3k-1)/2 Sk+1 = Sk + 3 (k+1) - 2 = (3 k^2 - k)/2 + 3 k +1 = (1/2)( 3 k^2 - k + 6 k +2 ) = (1/2)(3 k^2 + 5k + 2) = 1.5 k^2 + 2.5 k + 1
*April 17, 2015*

**chemistry**

same as last one I just did
*April 17, 2015*

**Chemistry**

molar mass of Mg(OH)2 = 24.3+2*17 = 58.3 g so we have .605/58.3 = .0104 mol molar mass of H2SO4 = 2+32+64 = 98 g so we have 1/98 = .0102 mol so we will get .0102 mol of MgSO4 .0102 ( 24.3+32+64) = 1.23 g
*April 17, 2015*

**PRE - CALCULUS**

You are welcome.
*April 17, 2015*

**PRE - CALCULUS**

S1 = 1(4)/2 = 2 check S2 = 2+5 = 7 = ? 2(7)/2 = 7 check S3 = 7+8 = 15 = ? 3 (1+9) /2 = 3*5 = 15 check
*April 17, 2015*

**Calculus**

I do not know - ask teacher. Unless we made arithmetic errors, that should be right. Perhaps in terms of pi or something ?
*April 17, 2015*

**Calculus**

we had A = 15.5 D - .897 D^2 and we know D = 8.64 A = 15.5 (8.64) - .897(8.64^2) = 67 ft^2
*April 17, 2015*

**Calculus**

h is height of rectangle1 31 = 2 h + D + pi D/2 2 h = 31 -D(1+pi/2) h = 15.5 - (D/2) (1+pi/2) area = D h + (1/2)(pi D^2/4) A = D (15.5 -1.29 D) + (1/8)pi D^2 A = 15.5 D - .897 D^2 dA/dD = 0 at max = 15.5 - 1.79 D D = 8.64 ft then h = 4.4 ft check my arithmetic !
*April 17, 2015*

**Math 222**

assume your x means * or "times"? multiply --- add exponents raise to power - multiply exponents a^.25 b^.5 * a^1 b^.5 a^1.25 b^1 or a^(5/4) b
*April 17, 2015*

**calc**

first second a = change in V/change in t = 29.32/1 second second a = (50.82-29.32) /1
*April 17, 2015*

**math**

6!/(6-2)! = 6*5 = 30 yes 8!/ [ 5! (3!) ] = 8*7*6/(3*2) = 56 sure enough
*April 17, 2015*

**math**

26.19/2845 = .0092056 times 365/12 = .28 times 100 = 28 %
*April 17, 2015*

**physics**

r = mv/qB double r ---> double v
*April 17, 2015*

**Vectors**

I assume this is three dimensional y (3x+1) = 0 y = 0 is a plane and x = -1/3 is a plane
*April 17, 2015*

**physics**

So, what do you think?
*April 17, 2015*

**math**

2 L + 2 w = 29 L = 1 + 2 w so 2 + 4 w + w = 29 5 w = 27 I have a sneaking suspicion that you have a typo because the text writers always make this stuff come out whole numbers.
*April 17, 2015*

**Physics**

eyes to mirror bottom to sole of shoe. They do not ask about top of mirror and top of head :)
*April 17, 2015*

**physics**

-9.81 m/s^2 0 = 20 - 9.81 t then h = 20 t - 4.9 t^2 or (1/2) m v^2 = m g h so h = v^2/2g
*April 17, 2015*

**physics**

m (v^2/r - 9.81)
*April 17, 2015*

**physics**

radial A = v^2/r tangential A = 7.9 they are perpendicular |A| = sqrt ( v^4/r^2 + 7.9^2 )
*April 17, 2015*

**Maths**

2/3 * 600 = 400 so 200 left after T shirt then 1/5 * 200 = 40 so 200 - 40 = 160 left to go home with
*April 17, 2015*

**math**

Any other line that intersects that one will do. It can not be the same line and it can not be parallel. You have -3 x + 2 y = 4 so change the sign of the x coefficient for example which changes the slope. +3 x + 2 y = 4 Now you have -3 x + 2 y = 4 +3 x + 2 y = 4...
*April 15, 2015*

**Pre - CALCULUS**

y = 5 x - 3 as x goes to 5 y ---> 22
*April 15, 2015*

**Physics**

Same answer as your other question.
*April 15, 2015*

**Physics**

eg: http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-007-electromagnetic-energy-from-motors-to-lasers-spring-2011/lecture-notes/MIT6_007S11_lec38.pdf
*April 15, 2015*

**Physics**

Google Heisenberg uncertainty principle certainty of product of position and momentum is limited so the more accurately you know position the less accurately you know momentum
*April 15, 2015*

**nope**

not without knowing the water temp at start
*April 12, 2015*

**physics**

power = voltage * current 20,000 * 50 = 500,000 i i = 50 (2/50) = 2 amps That is why you send big power at high voltage
*April 12, 2015*

**LINEAR EQUATIONS**

There is a limit to how many people I can help at once.
*April 12, 2015*

**LINEAR EQUATIONS**

c = a + b x or 100 = a + b(20) 122.5 = a + b(25) -------------------- 22.5 = 5 b b = 4.5 100 = a + 4.5*20 a = 10 so y = 4.5 x + 10 ----------------- now check if 25 wraps y = 4.5*25 + 10 = 122.5 sure enough
*April 12, 2015*

**Math**

However here the sum of any two must not be less than the third side or they will not reach b fails c fails d fails ONLY A passes :)
*April 12, 2015*

**math problem HELP ME**

Look at this scroll down to "algebraic proofs" http://en.wikipedia.org/wiki/Pythagorean_theorem
*April 12, 2015*

**math problem HELP ME**

(a-b)^2 + (4 a b/2) = a^2 - 2 a b + b^2 + 2 a b = a^2 + b^2 but as you know c^2 = a^2 + b^2 is the Pythagorean Theorem
*April 12, 2015*

**Math**

tan 40 = h/5 not much of a tree :)
*April 12, 2015*

**physics**

no your torque is not constant from 0 to 1 second it is Torque = 2 t for 0 to 1 second a = 2 t/2.5 v = (2/2.5)(t^2/2) = 1/2.5 rad/s at 1 second ------------------------ NOW that is your constant torque of 2 from 1 second to 2 seconds initial v = 1/2.5 rad/s a = dv/dt = 2/2.5 v...
*April 12, 2015*

**Vectors**

1) x = 1 + 2 s or s = (x-1)/2 y = 7 + 5 s y = 7 +(5/2)(x-1) 2y = 14 + 5 x - 5 5 x - 2 y = -9 now where does that hit 2) ? t = (x-3)/4 so y = (10/4)(x-3) + 12 4 y = 10 x - 30 + 48 10 x - 4 y = -18 so we have two equations 5 x - 2 y = -9 10 x - 4 y = -18 BUT THEY ARE the SAME ...
*April 12, 2015*

**physics**

Actually, I took the course in 1956 and do not need the practice. You do. Try and I am sure one of us will look your results over.
*April 12, 2015*

**math**

$1000 in and $400 out :) chance of winning = 1/500 value = 400/500 = 80 cents
*April 12, 2015*

**Algebra 1**

You are welcome.
*April 12, 2015*

**Algebra 1**

h = t (64-16 t) h is zero, ground, when t = 0 and when t = 4 t may not be - t may not be greater than 4 unless the arrow drops into a mine shaft so I would say 0</= t </= 4
*April 12, 2015*

**typo ?**

do you mean -16 t^2 + 16 t + 32 ???? all t, no x that in the obsolete foot, pounds, slugs units is the height of a projectile under gravitational force only. In that case 32 is the initial height in feet when t = 0
*April 12, 2015*

**Science**

thrust = rate of change of momentum mass per second in = 40 momentum per second in = 8000 mass per second out = 42 momentum per second out =42*600 = 25200 change of momentum per second = 17200 kg m/s^2 which is 17200 Newtons By the way, that is Newton #2 which you know better ...
*April 12, 2015*

**Physics**

Q = flow rate = pi r^2 V loses rho g h = 1000 kg/m^3 * 9.81 m/s^2 * 5.2 m in N/m^2 or Pascals it will go faster through the smaller pipe so loses pressure by Bernoulli Q2 = Q = pi r^2 V2 so V2/1.8 = 6.5^2/5.5^2 calculate V2 then pressure loss due to v increase is (1/2)(1000) (...
*April 12, 2015*

**Algebra 2 A**

y^2 + 6 y = 3 x - 3 y^2 + 6 y + 9 = 3 x + 6 (y+3)^2 = 3 x + 6 (y+3)^2 = 3 (x+2) vertex at (-2,-3) open to right
*April 12, 2015*

**Physics**

what is the period when the resonance occurs? T = distance/speed = 5 / 6.1 m seconds so frequency f = 1/T = 6.1/5 Now do your sqrt K/m thing
*April 12, 2015*

**Math**

hey ANY 2 dimensional figure if its scale is multiplied by x its AREA is multiplied by x^2 2^2 = 4 or in this case 2L * 2 w = 4 L w
*April 11, 2015*

**Math**

(4/3) pi r^3 = (4/3)pi(8) = 33.51 m^3 (1/3)(pi)(4)^2 (10) = 167.6 m^3
*April 11, 2015*

**Math**

3*36 + 2*12 + 8 = 140 inches (Sheila) 24*12 + 8 = 296 inches (record) =296-140 = 156 inches longer 156/12 = 13 feet longer
*April 11, 2015*

**algebra**

0/5 = 0 5/0 is very, very very big try on your calculator 5/ 0.00000001
*April 11, 2015*

**pre - CALCULUS**

34/5 + 11/5 + z = 9 ? z = 9 - 9 = 0 2 * 34/5 - 3 * 11/5 + 4z = 7 7 + 4 z = 7 z = 0 ah ha, B -7 z/5 + 2 z/5 + z IS ZERO LOL Talk about fooling the student !
*April 11, 2015*

**ah ha**

34/5 11/5 undefined 0 can not solve for z, bottom row all zero put arbitrary z in and see what happens
*April 11, 2015*

**pre - CALCULUS**

whoops, 2 not three in row 2 beginning put in +1 +1 +1 +9 +2 -3 +4 +7 +1 -4 +3 -2
*April 11, 2015*

**pre - CALCULUS**

Those answer choices are wrong
*April 11, 2015*

**pre - CALCULUS**

put in +1 +1 +1 +9 +3 -3 +4 +7 +1 -4 +3 -2 3 rows, 4 columns
*April 11, 2015*

**pre - CALCULUS**

0 , 29/7 , 34/7 it says http://www.gregthatcher.com/Mathematics/GaussJordan.aspx
*April 11, 2015*

**pre - CALCULUS**

strange answer choices, arbitrary z hang on
*April 11, 2015*

**pre - CALCULUS**

http://www.gregthatcher.com/Mathematics/GaussJordan.aspx
*April 11, 2015*

**pre - CALCULUS**

But there is a limit to what I am going to try to type
*April 11, 2015*

**pre - CALCULUS**

oh ho, now Gauss Jordan. We are cooking with gas here
*April 11, 2015*

**Pre - CALCULUS**

LOL, I have not finished You need to do the whole ting all you know is termm 11 and 21 so far whoops 12 not +12 so element 11 is 5/12 and element 21 is -1/6 looks like C
*April 11, 2015*

**Pre - CALCULUS**

left determinant is D = -12 first solution is for +1 -6 +0 -5 or -5/12 = element 11 then +0 +1 -2 +0 over -12 or 2/-12 = -1/6 = A21 then do the second
*April 11, 2015*

**Pre - CALCULUS**

well, it may be time to ask what method you are supposed to use. for example you seem to have Cramer's rule so A * A*-1 = 1 0 over 0 1 so solve with 1 over 0 on the right then with 0 over 1 on the right so for first column of inverse solve +0 x - 6 y = 1 -2 x - 5 y = 0 ...
*April 11, 2015*

**Pre - CALCULUS**

I mean 9 :)
*April 11, 2015*

**Pre - CALCULUS**

+2 +4 -1 +1 -2 +2 ---> -4+40-1 -10-4-4 = 17 yuuk +5 +1 +1 now solve for Y not x because your solutions set has all different y values :) +2 32 -1 +1 -5 +2 ---> --10+320-20 -25-80-32 = 153 +5 20 +1 then 153/17 = ( whew, D
*April 11, 2015*

**pre - CALCULUS**

yes -4 * -1 = 1 and -4*3 = -12
*April 11, 2015*

**pre - CALCULUS**

note the determinant of 2 1 6 3 is 6 - 6 = 0 therefore the solutions using Cramer's Rule are undefined
*April 11, 2015*

**physics**

volume of iron = (4/3)pi (Rout^3-Rin^3) mass of iron = (1 g/cm^3)(4/3) pi Rout^3 so density of iron = Rout^3/(Rout^3-Rin^3)
*April 11, 2015*

**math**

18(4/3) = 24
*April 11, 2015*

**maths**

10^x * 10^y = 10^(x+y) (to multiply add exponents if the base is the same)
*April 11, 2015*

**NEED HELP PHYSICS!!!**

Ac = v^2/r = v^2/10.5 F = m Ac 3.22 = .0822 v^2 /10.5 solve for v
*April 11, 2015*

**PHYSICS HELP PLEASE !!**

F = m a tension = mg + m v^2/r F = 78.4 (9.81 + v^2/10)
*April 11, 2015*

**Calculus(urgent please help)**

vertical asymptotes is easy because x = 3 or -3 makes function undefined where is slope + and where - ? slope = ([x^2-9]2x - x^2[2x])/[x^2-9]^2 denominator is always + or 0 when is top + and -? top is -18x so slope = -18x/positive number so slope is + if x is + and - if x is...
*April 10, 2015*

**pre - CALCULUS**

You are welcome.
*April 10, 2015*