Wednesday

July 29, 2015

July 29, 2015

Total # Posts: 21,565

**Math**

v = s^3 dv = 3 s^2 ds at s = 50 v = 125,000 dv = 3 (2500) ds = 7500(.1) = 750 100 (750/125,000) = .6 %
*December 29, 2014*

**Calculus- Can you help me solve for dr/dt**

You are welcome. Actually I am retired now :)
*December 29, 2014*

**Calculus- Can you help me solve for dr/dt**

The change of volume of a sphere with increasing radius is the surface area of the sphere times dr. Draw a picture ! In other words: dV = 4 pi r^2 dr so dV/dt = 4 pi r^2 dr/dt so here 15 = 4 pi r^2 dr/dt or dr/dt = 15 /(4 pi r^2) ---------------------- note , I am a ship ...
*December 29, 2014*

**geomentry**

Its volume is 27 times the old volume (3*3*3)
*December 28, 2014*

**Physics**

You are welcome. Remember potential is always a difference (In height, voltage, whatever).
*December 27, 2014*

**Physics**

10,000 meters the horizontal distance is irrelevant.
*December 27, 2014*

**^Maths^**

good point :)
*December 27, 2014*

**^Maths^ typo**

301 base 6 1*10^0 + 0*6^1 + 3*6^2 should be 301 base 6 1*6^0 + 0*6^1 + 3*6^2 = 109
*December 27, 2014*

**^Maths^**

By the way, I just did that by common sense. I do not know what routine you are really supposed to know. You may have a better way to shift back and forth.
*December 27, 2014*

**^Maths^**

451 base 6 1*6^0 + 5*6^1 + 4*6^2 = 1 + 30 + 144 = 175 in base 10 301 base 6 1*10^0 + 0*6^1 + 3*6^2 = 1 + 0 + 108 = 109 in base 10 so in base 10 175 - x = 109 x = 66 in base 10 put that in base 7 7^2 = 49 17 left 2*7^1 = 14 3 left so 1^7^2 + 2*7^1 + 3*7^0 or P = 123 in base 7
*December 27, 2014*

**physics**

Note equation 1.78 seems to be missing an = sign just left of the integral sign
*December 27, 2014*

**physics**

try deleting the s on https http://books.google.com/books?id=PTj2eEbT_jQC&pg=PA67&dq=elongation+of+long+hanging+rod+due+to+own+weight&hl=en&sa=X&ei=7TGfVI_7NcufgwSx-YKYCg&ved=0CGwQ6AEwCQ#v=onepage&q=elongation%20of%20long%20hanging%20rod%20due%20to%20own%20weight&f=false
*December 27, 2014*

**physics**

Looks like a MIT 8:01 problem to me :) It is too much for me at present but this link might help a little: https://books.google.com/books?id=PTj2eEbT_jQC&pg=PA67&dq=elongation+of+long+hanging+rod+due+to+own+weight&hl=en&sa=X&ei=7TGfVI_7NcufgwSx-YKYCg&ved=0CGwQ6AEwCQ#v=onepage&...
*December 27, 2014*

**Physics**

2.3/2 = 1.15 seconds to go up 0 = Vi -4.9 t = Vi - 4.9*1.15 Vi = 5.365 m/s initial speed up the second ball must have same initial vertical component of velocity = 5.365 m/s Vi sin 60 = 5.365 so Vi = 6.51 m/s
*December 27, 2014*

**PHYSICS**

initial momentum west = 1720 v -1510(75.7) = final momentum west = (1720+1510)15.5
*December 27, 2014*

**math**

LOL ali 3/8 * 80 = 30 5/8 * 80 = 50 30/50 = 3 / 5
*December 26, 2014*

**math**

3 + 5 = 8 so 30new + 50top
*December 26, 2014*

**math**

If a student keeps asking similar questions the student needs to look at earlier replies and try to do the next one without help Jack. We can then check the answer but just telling the student how to do it time after time helps not in the least.
*December 26, 2014*

**math**

yes, ok 24/9 = 8/3 same answer
*December 26, 2014*

**math**

24/36 = 2/3 (2/3)4 = 8/3 or 2 2/3
*December 26, 2014*

**math**

(1/4)(25)sqrt 3 = 10.8 cm^2
*December 26, 2014*

**physics**

How about different colors :) ?
*December 26, 2014*

**math**

pi r^2 = s^2 4 s + 2 pi r = 3600 it seems they want you to use x for 2 pi r so r = x/(2pi) pi r^2 = x^2/(4 pi) = s^2 so 4 s + x = 360 2x/( sqrt pi) + x = 360 2.13 x = 360 x = 169.1 cm 360 - x = 4s = 190.9 cm s = 47.7 ------------------------- check r = x/(2 pi) = 26.9 pi r^2...
*December 26, 2014*

**6th grade math**

1 serving = 0.8 cups 4 cups (1 serving/.8 cups) = 5 servings or 4 * 1/ (4/5) = 20/4 = 5
*December 26, 2014*

**science typo ?**

do you mean 220 volts ? i V = 2,000 220 i = 2000 i = 2000/220
*December 26, 2014*

**maths**

if sin A = 1/2 then cos A = (sqrt 3)/2 because that is a 30, 60, 90 triangle (1/8) 3 * 3^1/2- (3/2) * 3^1/2 = -(9/8) * 3^1/2
*December 26, 2014*

**physics**

1 kg * g = (3+4) a a = g/5
*December 25, 2014*

**binomial**

if only allowed up to x^3 do it in two steps result for (x+8y)^3 * (x+8y)^2 that is easier anyway
*December 25, 2014*

**Math**

Just graph a few points working both ways from ( 0 , -2 )
*December 24, 2014*

**Math**

when x = 0, y = -2 Y increases at 45 degrees from there in both directions so it is a V with the bottom point at (0 , -2)
*December 24, 2014*

**Algebra 2**

well, we know that sqrt 4 = 2 so the answer is (1/2) sqrt 3 however in general to clear the denominator: multiply top and bottom by sqrt 4 3 sqrt 3 sqrt 4 / (3*4) = 6 sqrt 3 /12 = (1/2) sqrt 3
*December 24, 2014*

**Physics**

The 90 kg student was standing still, momentum of zero. there was a push for .0003 seconds then his speed was 5 m/s so change in momentum = 90*5 - 90*0 = 90*5
*December 24, 2014*

**Physics**

force = change in momentum / change in time 90*5/.0003 in Newtons by the way .0003 is a very short pushing time, impractical I think. (typo?)
*December 24, 2014*

**CULCULS**

exactly. I am a Naval Architect. We have a hydrostatic characteristic called "tons per inch" which is how many tons of cargo you can add to increase the draft by one inch as a function of draft. It is basically the water plane area * density of seawater :)
*December 24, 2014*

**CULCULS**

v = (1/3) pi r^2 h but r = h/2 so dr = (1/2) dh v = (1/3) pi * 2 r^3 dv/dt = (2) pi r^2 dr/dt dv/dt = pi r^2 dh/dt Note: this is just the surface area * dh/dt
*December 24, 2014*

**Math**

12/4 = 3 4,000 * 1.03^48
*December 24, 2014*

**Algebra 1 - HEY!!!**

HEY, someone named Henry already showed you how to do this sort of problem. Now start doing them yourself. Post your answers.
*December 23, 2014*

**Algebra 1**

none those two lines have the same slope of 5 so they are parallel but they do not have the same y axis intercept so they never touch each other in two dimensional space.
*December 23, 2014*

**Algebra 1**

for heavens sake put your lines in the form y = m x + b and see if they have different m, slope then if so, see if b is the same for both.
*December 23, 2014*

**Algebra 1**

same slope, same y intercept so lines on top of each other, infinite number of points
*December 23, 2014*

**algebra**

g(7) = 2*7 = 14
*December 23, 2014*

**algerbra**

call the slope m then in general for any two points on a line of form y = m x + b the slope is change in y / change in x so for two points (x1 ,y1) and (x2 , y2) m = (y2-y1)/(x2-x1) the same is true for any other point on the line (x , y) so also m = (y2 - y) / (x2 - x) or m...
*December 23, 2014*

**Math; Please help**

vary inversely t = d/v
*December 23, 2014*

**Big History Test (Check) Part1.**

The North's well-established government gave it a distinct advantage. <-- I suppose, but the main thing was the industrial base in the north and navy and railroads. I would have checked: The goal of the war changed from saving the Union to saving the Union and ...
*December 23, 2014*

**Algebra**

You are welcome.
*December 23, 2014*

**Algebra**

####### r^2 + 5 r + 1 #######_______________________ (r-5) | r^3 + 0 r^2 - 24 r - 5 ####### r^3 - 5 r^2 #######_______________________ ############# 5 r^2 - 24 r - 5 ############# 5 r^2 - 25 r ############# ________________ #################### 1 r - 5 #################### 1 r...
*December 23, 2014*

**Algebra**

well, you could guess but it only took me a minute to do long division r^2 + 5 r + 1
*December 23, 2014*

**math**

LOL this is a perfect basketball and a perfect floor so all collisions are elastic and it bounce back up to 160 ft every time? Four round trips and a fall so 9 * 160
*December 23, 2014*

**Physics**

distance = rate * time :) speed east = Ve = 1.60 * cos 20.8 speed north = Vn = 1.60 sin 20.8 time east = 22/Ve time north = 31/Vn
*December 23, 2014*

**english**

hint maybe c a........ b e
*December 23, 2014*

**PHYSICS**

Hey - You are supposed to follow what I did, not just type any old number I give you!!!!! I did r = 3.19 You can multiply by 2 to get the diameter but you better decide to understand what I did first.
*December 22, 2014*

**algebra**

Yes :)
*December 22, 2014*

**algebra**

If you go 40 miles the first hour and 40 more the second hour how far did you go? Certainly NOT 20 !!!
*December 22, 2014*

**physics**

Ac = v2/R =omega^2 r = g/.7 =9.81/.7 = 14 r = 14/omega^2 but omega = 2 pi (1/3) = 2.09 radians/s omega^2 = 4.38 r = 14/4.38 = 3.19 meters
*December 22, 2014*

**Physics**

Huh? Sin(25)*187+(36*9.81) = 432.19 the clerk is pulling UP not down -Sin(25)*187+(36*9.81) =274.1 = normal force down on floor 274.1 * .410 = 112 so 187 cos 25 - 112 = 36 a
*December 22, 2014*

**math**

.75 * .7 = .525
*December 22, 2014*

**Earth science**

Isobars help me find fronts :) The cyclone is indeed counterclockwise in the Northern hemisphere (not south of the equator where the spin around a low is clockwise to conserve angular momentum). I agree with the rest
*December 22, 2014*

**Math and Phyics**

Tension T in rope, on big mass M g - T = M a while the big mass is falling, the little mass goes up a distance h when the big mass hits ground, the little mass is moving with the speed that the big mass hits with, then coasts up until the kinetic energy of that speed is spent...
*December 22, 2014*

**Math/Algebra 1**

string = 180 + 2 (necklace) if necklace = 10 string = 180 + 20 = 200 if necklace = 11 string = 180 + 22 = 202 if necklace = 12 string = 180 + 24 = 204 etc works fine
*December 22, 2014*

**Math/Algebra 1**

string = 200 + 2 (length of necklace - 10) or string = 180 + 2 length of necklace)
*December 22, 2014*

**redone**

v = 256 pi/3 = (4/3) pi r^3 so r = 4 S = v(3/r) = 4 pi r^2 = 64 pi v = (4/3) pi r^3 = S (r/3) = (1/3) S r dv/dt = (1/3) [ S dr/dt + r dS/dt ] but S dr/dt = dv/dt = 10 30 = 10 + 4 dS/dt 20 = 4 dS/dt dS/dt = 5 cm^3/s
*December 22, 2014*

**Calc**

V = (4/3) pi r^3 so when V = 256 * pi/(3) 256 pi/(3 ) = 4 pi r^3 /(3) r^3 = 64 r = 4 d v = surface area of sphere * dr dv = 4 pi r^2 dr = 64 pi dr dv/dt = 64 pi dr/dt = 10 cm^3/s dr/dt = 10/(64 pi) so dV/dt = 4 pi r^2 dr/dt = 10 so dr/dt = 10/(4 pi ) dS/dt = 8 pi r dr/dt = 32 ...
*December 22, 2014*

**Math and Phyics**

Is there no picture?
*December 22, 2014*

**Math and Physics - Huh ?**

There are two masses M and m ? They are at two vertices of the triangle? What is at the third corner?
*December 22, 2014*

**algebra**

You are welcome :)
*December 22, 2014*

**algebra**

check -2(8) - 7 -16 - 7 -23 sure enough :)
*December 22, 2014*

**algebra**

-2 v - 7 = -23 add 7 to both sides -2 v = -23 + 7 = -16 divide both sides by -2 v = -16/-2 = +8
*December 22, 2014*

**AP CALC**

sin 3 pi/2 = sin 270 = -1 sin - 3 pi/2 = +1 change in sin x = -1 - +1 = -2 change in x = 3 pi/2+3pi/2 = 3 pi so slope from left to right = -2 / 3pi = -.2122 so where does the derivative of sin x = -.2122 ? d/dx (sin x) = cos x so cos x = -.2122 x = 102.25 degrees = 1.78 radians
*December 21, 2014*

**Physics**

if initial speed in +x direction impulse = change of momentum .0420 (-7.4 - 18.3)
*December 21, 2014*

**ap calc**

when x = 2, y = 2(4)-8+3 = +3 when x = 0, y = 2(0) -0^2 = 0 delta y/delta x = (3-0)/2 = 1.5 so where in there does f' = 1.5 ? between 0 and 1 f' = 2 - 2x so 2 - 2x = 1.5 2x = .5 x = .25 is one spot between 1 and 2 f' = 4 x - 4 so 1.5 = 4 x - 4 4 x = 5.5 x = 1.375 ...
*December 21, 2014*

**Physics**

call + x direction the initial direction of the first (3 kg) mass initial momentum = 3*2 -5*2 =6-10 = -4 final momentum also -4, mass = 8 8 * v = -4 v = -1/2
*December 21, 2014*

**ap calc**

h = e^sin x h' = cos x e^sin x cos pi/2 = 0 sin pi/2 = 1 so 0 * 1 = 0
*December 21, 2014*

**been there done that**

I just did this a little while ago
*December 21, 2014*

**math**

0.34* 10^7 + 4.7 * 10^7 = 5.04 * 10^7 but you are only using 2 significant figures so 5.0 * 10^7
*December 21, 2014*

**math i really need help!!**

5.93 * 10^5 - 0.271 * 10^5
*December 21, 2014*

**College Math**

probably sqrt (30)
*December 21, 2014*

**physics**

Now this is very similar but easier than the one you threw up from the roof of the building. You try it. I have grand kids playing hockey now.
*December 21, 2014*

**physics**

That t top in part B is the time to slow down on the way up from the top of the building to the max height. 10/9.81 seconds. THEN, it starts falling from that top point I called Htop. By the way it will pass the roof on the way down at 10 m/s down :)
*December 21, 2014*

**physics**

v = Vi - 9.81 t v = 0 at top so t = 10/9.81 at top (part B) Htop = 150 + 10 t - 4.9 t^2 (part A) now simply drops from Htop to ground Pe at top = m g Htop Ke at bottom = (1/2) m v^2 so v = sqrt (2 g Htop) (part C) we have original t rising to top now time falling v = 0 + g ...
*December 21, 2014*

**math**

6/9 = 2/3 chance of not blue on each pick if replaced, then independent 2/3 * 2/3 * 2/3 = 8/27
*December 21, 2014*

**algebra**

2 s + 5 a = 950 s+a = 250 so a = 250 - s 2 s + 5 (250-s) = 950
*December 21, 2014*

**Physics- revolutions**

Ac = v^2/r so .7 = .013 v^2/.93 solve for v we know r time = distance / speed = 2 pi r/v
*December 21, 2014*

**phys**

F = m a = 70 * acceleration = 70 * 5 * 9.81
*December 21, 2014*

**Physics~**

You are welcome :)
*December 21, 2014*

**Physics~**

sqrt (ge/gm) = sqrt 6 times period on earth
*December 21, 2014*

**Physics**

.145 * 9.81 - .4 = 1.022 N down a = F/m = 1.022/.145 = 7.05 m/s^2 down I get
*December 21, 2014*

**Static Friction..I really Have no Idea**

maximum friction force = mu m g = .2 * .4 * 9.81 = .787 Newtons so it is less than or equal to .787 Newtons (or .78 N if you use 9.8 for g and round to two significant figures)
*December 21, 2014*

**chemistry**

p V = n R T p/RT = n/V = constant here n of H2/V of H2 = n of NH3/V of NH3 V of H2 = (n of H2/ n of NH3)100 cm^3 for every 2 mols of NH3 you get 3 mols of H2 so n of H2/n of NH3 = 1.5 so V = 1.5 * 100 = 150 cm^3
*December 21, 2014*

**Physics**

T - m g = m a T = 10.0 (9.81 + 1.50)
*December 21, 2014*

**Math**

8 + 3 = 11 37 + 15 = 52 so 11:52 pm
*December 21, 2014*

**Wolfram disagrees with me, check my algebra**

http://www.wolframalpha.com/input/?i=plot+xln%28x%29%2B+%281-x%29ln%281-x%29
*December 21, 2014*

**ap calc**

y = x ln x + ln(1-x) - x ln (1-x) = ln x^x + ln [ (1-x)/(1-x)^x = ln [ x^x (1-x)^1/(1-x)^x ] = ln [ x^x (1-x)^(1-x) ] let z = 1-x dz = - dx y = ln [ x^x z^z ] = ln x^x + ln z^z = x ln x + z ln z y' = x (1/x) + ln x + z(1/z)dz/dx + ln z dz/dx = 1 + ln x -1 - ln(1-x) = 0 all...
*December 21, 2014*

**ap calc**

y = sin x y' = cos x I guess that is -3 pi/2 to + 3 pi/2 sin 3 pi/2 = -1 sin -3 pi/2 = 1 -1 - 1 = -2 -1/(3 pi) = -.1061 cos^-1 -.1061 = 96.1 degrees = 1.677 radians cos is odd function so also -1.677 radians
*December 21, 2014*

**History**

He sent General Zachary Taylor to claim an area of disputed land for the United States. http://en.wikipedia.org/wiki/South_Pass_%28Wyoming%29 The journey was surprisingly easy. the idea that it was God's plan for the nation to expand across the continent
*December 21, 2014*

**Math-How do I do this problem?**

sure change in volume = surface area * change in depth or dV = pi r^2 dh dV/dt = pi r^2 dh/dt = 12 ft^3/min so dh/dt = 6/(pi r^2) if r = 7, h = 24 or r = (7/24)h = (7/24)(10) = 70/24 so dh/dt = 6 / [ pi (70/24)^2 ]
*December 21, 2014*

**physics**

two arrows right, one left <-.------>-->
*December 21, 2014*

**multiplcation**

6*1000 = 6000 6*700 = 4200 6*50 = 300 6 * 0 = 0 ------------------add 10500
*December 21, 2014*

**math**

p = price of kerosene/liter 5 p/3 = price of diesel 5 p = price of petrol x = liters of diesel purchased cost of x liters of diesel = 5 x p/3 = 510 cost of x liters of kerosene = x p but x p = (3/5)(510) = 306
*December 21, 2014*

**Calculus**

6 x dx + 2 y dy = 0 dy/dx = -3 x/y at (1,2) this is-3/2 d^2y/dx^2 = -3 [ y - x dy/dx ]/y^2 at (1,2) = -3[2+3/2]/4
*December 21, 2014*