Saturday

July 4, 2015

July 4, 2015

Total # Posts: 21,408

**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*

**calculus**

ln y = 3 x ln (x+8) (1/y ) dy/dx = 3x[1/(x+8)] + 3 ln(x+8) dy/dx = 3x(x+8)^3x {[1/(x+8)]+3 ln(x+8)}
*December 21, 2014*

**Calculus**

dy/dx = 2 x so -1/slope = -1/2x = -1/4 y = -x/4 + b 9 = -1/2 + b b = 9.5 y = -x/4 + 9.5 4 y = -x + 38
*December 21, 2014*

**Math**

dy/dx = 3 x^2 + 10 x -8 yes 0 d^2y/dx^2 = 6 x + 10 positive so min at 0 I get about .2 so not 0 so I think only A
*December 21, 2014*

**Physics- Horizontal Velocity**

You dropped it from 5 meters and it went 25 meters maybe ?? If so: time to drop 5 meters 5 = (1/2)(9.8)t^2 t = 1.43 seconds u = 25 m/1.43 s = 17.5 m/s
*December 21, 2014*

**Biology**

Sometimes mechanical (rubbing) , sometimes chemical (reacting with O2), etc. The one thing you can count on is that whatever happens, it will end up losing heat to the environment :)
*December 19, 2014*

**physics please help**

Bart does 400/60 m/s how many meters does he do in 58 s ? (when Wyatt finishes) 400 (58/60) = 386.66666666666666666667 400 - that = 13.3333333333 meters
*December 19, 2014*

**NEED HELP ASAP PHYSICS**

35.79 miles per hour { Google 16 m/s = miles/hour } a = change in velocity/change in time = -16/.08 = -200 m/s^2
*December 19, 2014*

**did that**

see question above
*December 19, 2014*

**physics**

stuff shoots out the rear, body moves forward Conservation of momentum (Newton #1) initial momentum before reaction = 0 so momentum of body/exhaust system remains zero forever therefore if exhaust moves back then body must move forward to keep the total momentum zero
*December 19, 2014*

**Helppp**

1 2 3 4 5 ---- 5.5 ---- 6 7 8 9 10 1 2 3 4 5 ----- 6 ----- 7 8 9 10 11 so A = 5.5 B = 6 11.5/2 = 5.75
*December 19, 2014*

**math**

No, .025*2,015,000 is the commission. You wrote what the seller gets after commission.
*December 19, 2014*

**Juba Day SS**

10/20 * 9/19 10/20 * 3/19 7/20 * 3/19
*December 19, 2014*

**PRE-ALGEBRA MRS.SUE PLEASE!!!!!!!!!**

Did you read my answer below? I have answered this question twice. 59.95/11.99 = 5 so you can buy 5 you can also buy four or three or two or one or none
*December 18, 2014*

**PRE-ALGEBRA MRS.SUE PLEASE!!!!!!!!!**

We can not always answer instantly.
*December 18, 2014*

**PRE-ALGEBRA MRS.SUE PLEASE!!!!!!!!!**

Check below you are fine except for #8 and #10
*December 18, 2014*

**PRE-ALGEBRA**

59.95/11.99 = 5 so you can buy 5 you can also buy four or three or two or one or none Please do not submit the same question twice !
*December 18, 2014*

**PRE-ALGEBRA**

1. 7 yes 2. 8 yes 3. 7x + 5 = 4x + 5 + 3x yes 5. k < 0 yes 6. q ≥ –1 yes 7. p < 8 yes 8. g > –90 #####I get g >90#### 9. n – 6 ≥ 2; n ≥ 8 yes 10. ??????? n </= 5 you could buy one or 4 but not 6
*December 18, 2014*

**Algebra 1**

since 7 x and -7 x appear just add the two equations to eliminate x like: 3 y = 3
*December 18, 2014*

**Math**

n/(n+1) (n+2) /[(n+1)+2 ] = 4/5 (n+2) / (n+3) = 4/5 5(n+2) = 4(n+3) 5 n + 10 = 4 n + 12 n = 2 2/3
*December 18, 2014*

**Science yes, agree**

Check my answers please? Imagine that you remove all the atoms from a chair. What remains? 1. nothing 2. a pile of dust I choose 1. YES Which of the following is not made of atoms? 1. heat 2. a solid 3. a gas I choose 1. YES What about matter is true? 1. atoms are not matter ...
*December 18, 2014*

**Algebra 1**

x-1 = -3x -5 4 x = -6 x = -1.5 y also negative yes quad three
*December 18, 2014*

**math**

or we could say 3/4 = Juice /(32-juice)
*December 18, 2014*

**math**

there are 3+4 = 7 parts
*December 18, 2014*

**math**

(3/7)32
*December 18, 2014*

**statistics**

http://davidmlane.com/hyperstat/z_table.html
*December 18, 2014*

**algebra 1**

use FOIL or distributive property (same thing really) 7 p^2 + 10 p + 3 or 7p (p+1) + 3 (p+1) = 7 p^2 + 7 p + 3 p + 3 = 7 p^2 + 10 p + 3 again
*December 18, 2014*

**math**

5 years = 20 quarters at .05/4 = .0125 per quarter 1.0125^20 = 1.282037232 so 55,000/1.282037232 = $ 42,900.47
*December 18, 2014*

**Honors Physics**

Try to answer and we will look.
*December 18, 2014*

**Honors Physics**

Honors physics?
*December 18, 2014*

**algebra 1**

10 x - 24 y = -6 10 x - 4 y = -25 ----------------- 0 x - 20 y = 19 y = -19/20 etc
*December 18, 2014*

**phy**

a up on 6 kg mass, so down on 10 kg mass 6 kg mass T - 6 g = 6 a 10 kg mass 10 g - T = 10 a add 4 g = 16 a a = g/4 then go back T - 6 g = 6 g/4 T = 7.5 g = 7.5(9.81)
*December 18, 2014*

**algebra**

40 + n = 10 + 4 n 30 = 3 n
*December 18, 2014*

**Math**

.65 * 80 100 (.65*80)/327
*December 18, 2014*

**Math**

(4x-1)/[(x+3)(x+4)] * (x+4)(x-3)/(2x-1) the (x+4) cancels, not much else to do
*December 18, 2014*

**Math**

I think it just blows up if x = -3
*December 18, 2014*

**Math**

x(x-2) /(x+1) * (x+1)(x-1)/[(x+3)(x-2)] = x (x-1)/(x+3)
*December 18, 2014*

**math solution on algebra**

half this triangle is a 30, 60, 90 triangle with the altitude (sqrt 3) as the long leg and half(1) the base as the short leg. (1/2) b h = (1/2)(2) sqrt 3 = sqrt 3
*December 18, 2014*

**physics**

Vi = 54 sin 39 v = Vi - 9.8 t v = 0 at top so t = Vi/9.8 at top use that t h = Vi t - 4.9 t^2 it will turn out to be 1/2 Vi t
*December 17, 2014*

**Please look for reply before posting again**

I did that a lot of questions ago.
*December 17, 2014*

**physic**

http://www.jiskha.com/display.cgi?id=1418842081
*December 17, 2014*

**physic**

been there, done that
*December 17, 2014*

**calculus honor**

assume you mean y = 2 x^3 - 4 x dy/dx = 6 x^2 - 4 if x = 1 dy/dx = 6-4 = 2
*December 17, 2014*

**calculus honor**

V = x^2 h dV/dx = 2 x h dV/dh = x^2 dV/dt = dV/dx dx/dt + dV/dh dh/dt x = 4 h = 15 dV/dt = 120 dx/dt + 16 dh/dt = 120(2) -16(3) = 240-48
*December 17, 2014*

**done that**

I did this one a while ago as well :(
*December 17, 2014*

**calculus**

A = pi r^2 A/dr = 2 pi r (which is the circumference of course, draw a circle and a ring of thickness dr on the outside and look at the added area) if r = 5 dA/dr = 10 pi =================== this is most interesting if the radius is changing with time r = k t dr/dt = k dA/dt...
*December 17, 2014*

**physic**

power = work/time work = weight * distance up = 475*9.81*10 so power = 475*9.81*10 / 24 Joules/second or Watts divide by 1000 for kilowatts
*December 17, 2014*

**Math( Can you help me with starting this problem)**

dV/dr = area of surface = 4 pi r^2 so dV/dt = 4 pi r^2 dr/dt so dr/dt = (dV/dt) / (4 pi r^2)
*December 17, 2014*

**Physics**

If .392 Newtons is pulling it at constant speed then the friction is equal and opposite to the pull .392 = mu m g = mu (.2219)(9.81)
*December 17, 2014*

**Algebra**

height = 5 (L-10)(w-10)5 = 1760 (L-10)(w-10) = 352 L = 2 w (2w-10)(w-10) = 352 (w-5)(w-10) = 176 w^2 - 15 w + 50 = 176 w^2 - 15 w - 126 = 0 (w-21)(w+6) = 0 so w = 21 L = 42
*December 17, 2014*

**Algebra 1**

slope = m = 3 10 = 3 (2) + b b = 4 y = 3 x + 4
*December 17, 2014*

**Physics**

If the angle is 90 degrees to the x axis it is all y axis 0 i + 9 j
*December 17, 2014*

**Science-Physics**

500 * 5 force in direction of motion times distance moved
*December 17, 2014*

**physics**

300 * 9.81 * 6 Joules
*December 17, 2014*

**Physics**

500 cos 37 - .5 (350 + 500 sin 37) = m a m = 350/9.81 find a 4 = (1/2) a t^2 for part be find mu for: 500 cos 37 - mu (350 + 500 sin 37) = 0
*December 17, 2014*

**Physic**

potentials add Q1/r = Q2/(.5-r)
*December 17, 2014*

**physics**

g = 9.81 m/s^2
*December 17, 2014*

**Physics**

51 = 4.9 t^2 solve for t d = 31 t v = 9.81 t vertical and 31 horizontal so speed = sqrt ( v^2+31^2)
*December 17, 2014*