Wednesday

October 1, 2014

October 1, 2014

Total # Posts: 18,728

**physics**

dv/dt = -kv dv/v = - k dt ln v = - k t + c e^ln v = v = e^(-kt +c) = e^c e^(-kt) when t = 0, v = Vo Vo = e^c e^0 = e^c so v = Vo e^-kt
*August 19, 2014*

**physics**

2 seconds rising and 2 seconds falling h = (1/2)g t^2 falling 10 = (1/2) g (4) = 2 g g = 5 m/s^2
*August 19, 2014*

**physics**

it evidently goes forward a distance 3d then back a distance 2d to end up a displacoutup to be negative. deceleration phase out to 3 d t1 = time out to 3 d v = Vi + a t1 0 = Vi + a t1 so t1 = -Vi/a 3 d = Vi t1 + (1/2) a t1^2 3d = -Vi^2/a + .5 Vi^2/a = -.5Vi^2/a d a = -(1/6) Vi...
*August 19, 2014*

**Language Arts**

I can not see your italics but suspect it is the "ing" and D is correct. http://en.wiktionary.org/wiki/present_participle
*August 19, 2014*

**math**

5 y + 7 x = 31 x y 5 y + 7 x = 29 x y well, (0,0) would work but then we would be dividing by zero in the original.
*August 19, 2014*

**English**

"His questions revealed an intelligence" seems to be the main idea so what is the rest ? http://www.chompchomp.com/terms/relativeclause.htm
*August 19, 2014*

**english**

http://www.merriam-webster.com/dictionary/tally
*August 19, 2014*

**P.E**

I figure my natural crabbiness is likely to be fatal, perhaps even to me.
*August 19, 2014*

**P.E**

Certainly
*August 19, 2014*

**english**

Let me see: He spread the rumor widely. ------> He spread the rumor most widely ?
*August 19, 2014*

**math**

There are six numbers so add them all up and divide the sum by six.
*August 19, 2014*

**Philippine history**

http://www.academia.edu/4833169/Continued_Filipinization_in_the_Late_20th_Century_The_Case_of_the_Ateneo_de_Manila_University_1968-1991
*August 19, 2014*

**Philippine history**

http://prezi.com/cfw8l09tjkas/filipinization-policy/ When the US defeated the Spanish in the Spanish American War, the Philipines ceased to be a Spanish colony and came under the US. The US made an effort to let the indigenous people take over ruling their islands replacing ...
*August 19, 2014*

**Physics**

All I can do is tell you the method. call M1 the mass of the one that is on string at 50 degrees from vertical (aI assume from vertical Then gravity force down slope is M1 g cos 50 T is up slope net force down is (M1 g cos 50 -T) same deal for M2 net force down is (M2 g cos 30...
*August 19, 2014*

**Physics**

I do not understand this geometry. Is the big one trying to drop down a 53 deg slope and the little one being dragged up a 30 degree slope or what?
*August 19, 2014*

**Physics**

The table is three football fields long and three football fields high? I bet it was 0.15 seconds actually :)
*August 19, 2014*

**Physics**

big table :)
*August 19, 2014*

**Physics**

F = 20 * 9.8 m = 50 + 20 = 70 a = F/m = 2.8 m/s^2 force on falling 20 kg mass = 20 (9.8) - T = m a = 20(2.8) so T = 140 Newtons d = (1/2) a t^2 = (1/2) 2.8 (225) = 315 are you sure you did not mean 1.5 seconds?
*August 19, 2014*

**science**

probably at least on a cell scale.
*August 19, 2014*

**Second law of motion**

Net force up = 35 - 25 = 10 Newtons F = m a m = 25/9.8 = 2.55 kg so a = 10 / 2.55 = 3.92 m/s^2
*August 19, 2014*

**Physics**

Good grief, English units, have to put mass in slugs and use seconds and pounds and feet. (Back to freshman year in 1955) change in speed = 40 miles/ hr *5280 feet/mile * 1 hr/3600 seconds = 58.7 feet per second mass in slugs = 3000 lb /32 ft/s^2 = 93.8 slugs F = change in ...
*August 19, 2014*

**Science**

north velocity = 30 (assume west wind so blowing plane east) east velocity = 40 total speed = sqrt (30^2+40^2) = 50 km/hr tan angle east of north = 40/30 angle east of north = 53.1 or about northeast by east (NExE)
*August 19, 2014*

**Physics**

F down slope = m g sin 35 a = F/m = g sin 35 = 9.8 sin 35
*August 19, 2014*

**math**

a + a r + a r^2 + a r^3 + a r^4 ....+a r^(n-1) so a r = 1.5 a r^4 = .1875 a = 1.5/r (1.5/r) r^4 = .1875 r^3 = .125 r = .5 a = 1.5/.5 = 3 so 3 + 1.5 + .75 ......
*August 19, 2014*

**science**

Huh ?
*August 19, 2014*

**Parabola**

axis of symmetry is halfway between 2 and 3 or x =2.5 to get the zeros of y at x = 2 and 3 y = k (x-2)(x-3) to get y = 6 at x = 0 6 = k (-2)(-3) k = 1 so y = x^2 -5 x + 6 (answer) check if vertex is at x = 2.5 by completing the square y -6 = x^2 - 5 x y - 6 + (5/2)^2 = x^2 - 5...
*August 19, 2014*

**Maths**

(1-e^-x) integral (1-e^-y) dy from 1 to 2 (1-e^-x) [ y + e^-y ] at 2 - at 1 (1-e^-x) [ 1 + (e^-2 - e^-1) ] (1-e^-x) [ .767 ] integrate that dx from 1 to 3 [ .767 ][ x + e^-x] at 3 - at 1 [ .767 ] [ 2 + (e^-3 - e^-1) ] [ .767 ] [ 1.68 ] 1.29 divide by area to normalize area = 2...
*August 19, 2014*

**algebra**

I do not dare because I bet you have typos. For example I would be surprised if -1^2 is not supposed to be (-1)^2.
*August 19, 2014*

**physics**

no s = -16 t^2 + 64 t If the ball left the ground with velocity + 64 ft/x then it returns to earth with velocity -64 ft/s. Your parabola is symmetrical and the vertex is at the top,
*August 19, 2014*

**Math**

Sorry, can not email to you. The word compass bearing is used correctly here. tangent of angle north from west axis = 70/145 tan^-1 (70/145) = 26 deg so bearing = 270+26 = 296 degrees clockwise from North this is approximately west north west
*August 18, 2014*

**math**

Henry, The 30 degrees is from North (the y axis), not from east (the x axis as in math convention).
*August 18, 2014*

**math**

^&%#*& mathematicians ! He flies on a HEADING of 030 east of north, NOT a bearing. You take a bearing on something, its direction from you. You sail or fly a compass HEADING. anyway East components are 90 sin 30 +150 =90 * (1/2) + 150 = 45 + 150 = 195 km east of start
*August 18, 2014*

**math**

actually the express train from Delhi to Meerut seems to go about 44 km/hr by the way: http://indiarailinfo.com/search/new-delhi-ndls-to-meerut-cantt-mut/664/0/1546
*August 18, 2014*

**math**

they approach each other at 180 km/h 75 km * (1 h/180 km) = .4167 h * 60 min/h = 25 minutes so 8:25 am
*August 18, 2014*

**social studies**

http://dictionary.reference.com/browse/xenophobia
*August 18, 2014*

**social studies**

Thank you Lexie Bowles. That was fun !
*August 18, 2014*

**social studies**

http://civilliberty.about.com/od/immigrantsrights/tp/Xenophobia-in-United-States.htm
*August 18, 2014*

**social studies**

http://en.wikipedia.org/wiki/Anabasis_%28Xenophon%29
*August 18, 2014*

**math**

50 in 125 and 30 in 90?
*August 18, 2014*

**math**

9 + 63 = 72 using rounding which happens to be exact and I also call 9 and 63 compatible numbers since adding 9 to anything is super easy.
*August 18, 2014*

**physics**

V defined as speed out of the barrel time rising = time falling so find rise time and multiply by 2 vertical problem: Vi = V sin 30 = .5 V v = Vi - 9.8 t v = 0 at top 0 = .5 V - 9.8 t so t = .5 V/9.8 and 2 t = total time aloft = V/9.8 at max height there is no vertical ...
*August 18, 2014*

**physics**

You are welcome :)
*August 18, 2014*

**physics**

if none were added dN/dt = k N number produced per second = 10 number lost per second = k n so dN/dt = 10 - k N N is maximum when dN/dt = 0 0 = 10 - k (1000) k = .01 so we know that for this fission reaction (without the inflow) dN/dt = -.01 N dN/N = -.01 dt ln N = -.01 t + C ...
*August 18, 2014*

**probability**

first red = 8/24 second blue = 4/23 so (1/3)(4/23) = 4/69
*August 17, 2014*

**Engineering maths**

outside dimensions of deck are L and W inside dimensions of deck are 30 and 22 so Area of deck = L W - 660 so L W - 660 = 480 L W = 1140 if x = deck width Length L = 30 + 2x W = 22+2x so (22+2x)(30+2x) = 1140 multiply out and solve quadratic
*August 17, 2014*

**physics**

I think they mean total acceleration up
*August 17, 2014*

**physics**

Vi = a t = 32 * 4.1 = 131 m/s at burn out h = (1/2)32 (4.1)^2 = 269 meters at burn out then v = Vi + a t at top v = 0 0 = 131 - 9.8 t t = 13.4 seconds coasting up h = 269 + 131 (13.4) -4.9 (13.4)^2
*August 17, 2014*

**computers**

Yes, http://www-03.ibm.com/ibm/history/exhibits/pc25/pc25_birth.html
*August 17, 2014*

**computers**

As I remember Microsoft
*August 17, 2014*

**important math question**

http://archives.math.utk.edu/visual.calculus/3/newton.5/
*August 17, 2014*

**important math question**

sorry, x - y / dy/dx
*August 17, 2014*

**important math question**

Newton's method for finding zeros f(x) = x^3 -x-5 pick an x in the range, say x = 2 f(2) = 1 f'(2) = 3 x^2 - 1 = 11 mark that point (2,1) and slope of 11 through it now that slope will hit the x axis at x + y / dy/dx or 2 + (-1)/11 = 1.909 now repeat again and again ...
*August 17, 2014*

**important math question**

Did you click on the polynomial calc link? You can use Newton's method. I will give you a link in a minute. Oh, no need, this next problem is in fact Newton's method. Draw a sketch f(3) = 5 Put an x at (3,5) slope ay (3,5) = -2 f(x+dx) = f(x) + slope * dx f(3 + .02) = ...
*August 17, 2014*

**typo**

1.90416
*August 17, 2014*

**important math question**

The only real root is x = 1.0416 http://www.mathportal.org/calculators/polynomials-solvers/polynomial-roots-calculator.php
*August 17, 2014*

**trigonometry**

draw a sketch cos 68 = x/43
*August 17, 2014*

**Algebra**

Every integer is a rational number because you can divide it by one.
*August 17, 2014*

**Precalculus**

at least one typo 2Z-W=(2Zx-Wx)i+(2Zy-Wy)j |2Z-W|^2=4Zx^2-4ZxWx+Wx^2+4Zy-4ZyWy+Wy^2 =4|Z|^2+|W|^2 -4(ZxWx+ZyWy)= 625 and |Z+2W|^2 =|Z|^2+4|W|^2 +4(ZxWx+ZyWy)=25 so 625+25 =5[ |Z|^2+|W|^2| ] or 130 = |Z|^2 + |W|^2 now that last one |Z+W|^2= Zx^2+2ZxWx+Wx^2+Zy^2+2ZyWy+Wy^2] = 4 ...
*August 16, 2014*

**Precalculus**

You asked for it: 2Z-W=(2Zx-Wx)i+(2Zy-Wy)j |2Z-W|^2=4Zx^2-4ZxWx+Wx^2+4Zy-4ZyWy+Wy^2 =4|Z|^2+|W|^2 -4(ZxWx+ZyWy)= 625 and |Z+2W|^2 =|Z|^2+4|W|^2 +4(ZxWx+ZyWy)=25 so 625+25 =5[ |Z|^2+|W|2| ] or 130 = |Z|^2 + |W|^2 now that last one |Z+W|^2= Zx^2+2ZxWx+Wx^2+Zy^2+2ZyWy+Wy^2] = 4 ...
*August 16, 2014*

**mathematics**

well lets see 14 23 32 41 50 could be 23 or 41
*August 16, 2014*

**Physic - Oh well, Google might help**

http://antoine.frostburg.edu/chem/senese/101/measurement/faq/indiana-jones.shtml
*August 16, 2014*

**Physic sorry :(**

LOL, can not help with this, did not see movie !
*August 16, 2014*

**Math**

ALMOST !!! sign error - dx /[(x+dx+3)(x+3) ] divide by dx -1/[(x+dx+3)(x+3) ] now let dx -->0 -1/(x+3)^2 which any calculus text will tell you is the right answer d/dx (1/u) = [bottom*d top - top d bottom]/bottom squared
*August 16, 2014*

**Math**

oh, much more fun !
*August 16, 2014*

**Math**

sqrt 2/ 4 = .35355 which is what our table and graph said
*August 16, 2014*

**Math**

no it is one quarter of the square root of 2
*August 16, 2014*

**Math**

Now that was fun but you do the next one :)
*August 16, 2014*

**Math**

sorry 1/ [2 sqrt2) multiply top and bottom by sqrt 2 to rationalize and we get (sqrt 2) / 4 as we knew all along
*August 16, 2014*

**Math**

x y 1.0 .318 0.5 .334 0.2 .345 0.1 .349 .05 .351 .02 .353 .01 .353 .001 .35351 etc which looks much like (sqrt 2 )/4 [(x+2)^.5-2^.5]/x * [(x+2)^.5+2^.5] ----------------------------------- [(x+2)^.5+2^.5] [(x+2) -2] = ------------- x [ (x+2)^.5+2^.5] = 1/ [(x+2)^.5+2^.5] which...
*August 16, 2014*

**Math**

http://www.wolframalpha.com/input/?i=%28%28x%2B2%29^.5-2^.5%29%2Fx
*August 16, 2014*

**Math**

You are welcome.
*August 16, 2014*

**Math**

By the way since this particular function is linear, constant slope, there was no need for us to take the limit to find the derivative (slope at x is slope at any x)
*August 16, 2014*

**Math**

this is the definition of the derivative f(x+dx) = 3(x+dx)-2 = 3 x + 3 dx -2 f(x) = 3 x - 2 f(x+dx) - f(x) = 3 dx divide by dx = 3
*August 16, 2014*

**fitness**

I do not know what to say :(
*August 16, 2014*

**fitness**

Having already found differing answers to these questions online, I think you better use the ones in your text book.
*August 16, 2014*

**Algebra**

2.5 * 144
*August 16, 2014*

**fitness**

Question 3 I suppose they mean the average baby.
*August 16, 2014*

**fitness**

Please post answers when you find them :)
*August 16, 2014*

**physical**

the deaths from heart, cancer and stroke, but they add to 50% which is not on your list of answers.
*August 16, 2014*

**physical**

That same site has the answer to question 2 in a link.
*August 16, 2014*

**geometry**

Must be less than 3+5 and more than 5-3
*August 16, 2014*

**geometry**

2 2 3 3 3 1
*August 16, 2014*

**Math**

by "right" do you mean "right triangle" ? If so then tan B = b/a B = tan^-1 (b/a)
*August 16, 2014*

**calculus**

Hey, you are doing great ! These last two were harder than the ones you asked for help with.
*August 16, 2014*

**calculus**

good, that is a long one :) add, then multiply, then add
*August 16, 2014*

**calculus**

3 min = 180 seconds downstream = 5 * 180 across = 12 * 180 hypotenuse = sqrt (across^2 + downstream^2)
*August 16, 2014*

**calculus**

in the x direction 6 * 1 = 6 int the y direction 2 * -4 = -8 in the z direction 0 * 1 = 0 6 + -8 = -2 see: http://www.mathsisfun.com/algebra/vectors-dot-product.html to see how to do it with |A| * |B| * cos theta
*August 16, 2014*

**Physic**

hard to say without knowing the volume. duck it in a full cup and measure the amount of water that flows over the lip.
*August 16, 2014*

**Physics 2**

Hard to say without knowing the distances... In general F = k Q1 Q2 /|R^2| iin direction of R If horizontal length = a and vertical height = h Q is lower right Q1 is lower left Q2 is upper left Q3 is upper right R is vector from Q to one of the other 3 Rx = x component of R Ry...
*August 16, 2014*

**Algebra**

I am not sure your superscript shows up on everyone's screen. 5 (14-20)^2 /2 = 5 * 36 /2 = 5 * 18 = 90
*August 16, 2014*

**physics, mit 2.01x, mechanical engineering**

If you tried to copy and paste the drawing or sketch of this truss here, it did not work because copy and paste is not allowed here. From what you said, moment of inertia of the cross section must be increased or length of section reduced assuming you are doing Euler column ...
*August 15, 2014*

**math**

how many buggies? 21 = 9 + 3 n n = 4 4*4 = 16 21 - 16 = 5
*August 14, 2014*

**Math**

1+2+3 average is (1+3)/2 = 2 2*3 = 6 check :) so I think it is (1+31)/2 = 16 16*31 = 496
*August 14, 2014*

**math**

-2 = -1/.5 so they are perpendicular, yes, C
*August 14, 2014*

**math corrections**

profit, p = revenue, r - cost, c r = revenue = 25 g c = cost = 75 so p = 25 g - 75 so if p >/= 50 then 25 g - 75 >/= 50 so you are right. It is E.
*August 14, 2014*

**math**

4.85/4 = 1.21625 = quarterly percent 11 years = 44 quarters (1.0121625)^44 = 1.7022 3,500 * 1.7022 = 5957.70 so agree. I do not see any list of staetements
*August 14, 2014*

**mathematics**

x+6
*August 14, 2014*

**math corrections**

I agree with your answer, C and have no idea why it is called incorrect.
*August 14, 2014*

**math corrections**

1, 5c 2 10 c 3, 15 c 4, 25c 5 30C 6 35 c 7 40 c 8 50 c 9 55 c 10 60 c 11 65 12 75 c 13 80 c 14 85 c 15 90 c
*August 14, 2014*

**math**

4000/7 = 571.4 so we need a little more than 571 572 will do 572 * 7 = 4004, check :)
*August 14, 2014*

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