Saturday

August 23, 2014

August 23, 2014

Total # Posts: 17,988

**physics**

77.9 = 10 log I/10^-12 = log I/10^-11 7.79 = log (I*10^12) 10^7.79 = I * 10^12 6.17 * 10^7 = I * 10^12 I = 6.67 * 10^-5 W/m^2
*June 21, 2014*

**EXCEL 2010 (again)**

I just tried =sum(C3:C9)/7 and it worked
*June 21, 2014*

**physics**

1) do it the same way I did the previous question 1 2) (bottom derivative top - top derivative bottom ) / bottom squared ( x^4 * 0 - 1*4x^3 )/x*8 = - 4 /x^5 3) x^2 cos x - sin x (2x) you finish
*June 20, 2014*

**physics**

1) 0 + 5 + 21 x^2 2) tan x (d cos^2 x /dx)+ cos^2 x d tan x / dx = tan x (-2 sin x cos x) + cos^2 x (sec^2 x) = -2 sin^2 x + 1
*June 20, 2014*

**physics**

Use parentheses to show what is numerator and what is denominator.
*June 20, 2014*

**Math**

1600 grams/3000 grams
*June 20, 2014*

**physics**

Hey, I told you how to do these yesterday except number 4 which is incomprehensible without adding parentheses and telling me what is u and what is du. Come on, we are volunteers here. integral x^4 dx = (1/5) x^5 + c integral 1 dx = x + c sum = (1/5) x^5 + x + c
*June 20, 2014*

**PHYSICS**

Come to think of it, anywhere at equinox you will have three hours light and three hours dark
*June 20, 2014*

**PHYSICS**

angular momentum remains the same. I2 omega 2 = I1 omega 1 I = constant * m R^2 If m2 = m1 and R2 = .5 R1 then m R2^2 = .25 m R1^2 and I2 = (1/4) I1 (1/4)I1 omega2 = I1 omega1 omega2 = 4 omega1 T2 = (1/4) T1 day is 6 hours long instead of 24 so at the equator at equinox we ...
*June 20, 2014*

**maths trigonometry**

tan T = 8/7 = sin T/cos T 8 cos T = 7 sin T ----------------------------- (1+cos T)(1-cosT) __________________ (1-sin T) (1+sin T) that is easy 1 - cos^2 T ____________ (1 - sin^2 T) but 1-cos^2 = sin^2 and 1 - sin^2 = cos ^2 so sin^2 T/cos^2 T = tan^2 T = 8^2/7^2 = 64/49
*June 20, 2014*

**math**

602234
*June 19, 2014*

**math**

987431
*June 19, 2014*

**math**

LOL, nah 0.500005
*June 19, 2014*

**Algebra can you give me direction**

on your graph paper put a big dot on the point where x = 3 and y = 5 now go right 2 and up 1 to x = 5 and y = 6 in other words(5,6) make another big dot there draw a line of infinite length through the two dots :) if you want the equation then y = m x + b 5 = (1/2)(3) + b
*June 19, 2014*

**Health**

http://www.webmd.com/bipolar-disorder/guide/bipolar-2-disorder bipolar 2
*June 19, 2014*

**Chemistry**

CaO + CO2 --> CaCO3 atomic masses Ca = 40 O = 16 C = 12 so CaO is 40 + 16 = 56 grams/mol 28/56 = .5 mol so we get .5 mol of CaCO3 CaCO3 = 40 + 12 + 48 = 100 grams/mol so we get 50 grams of CaCO3
*June 19, 2014*

**probability**

Binomial distribution p(success) = .9 1-p = .1 P(29 out of 30) = C(30,29) * .9^29 * .1^1 C(30,29) = 30! / [ 1! (29!) ] = 30 so 30 * .9^29 * .1 = .1413
*June 19, 2014*

**physics**

1. is integral x^4 dx + integral x dx 2. same deal, split into sum of two integrals integral of cot^2 x = (-1/x)cot x - x 3. yet again cos*sin/cos = cos :) cos * 1/cos = 1 :) 4. I think you have a typo and I do not know what is u and what is du or actually what is in the ...
*June 19, 2014*

**Physics**

calculate I of solid disc omegai = 90 rev/min * 2 pi rad/rev * 1 min/60 s = 9.42 radians/second Ke = (1/2) I omegai^2 at start, zero at finish Torque = 4 R = 4*.34 newton meters alpha = Torque/I omega = omegai - alpha t omega = 0 at finish so t = omegai/alpha which is time to ...
*June 19, 2014*

**typo**

Huh?
*June 18, 2014*

**Physics**

mg = 83.8*9.81 = 822.1 N so Fdown = 822.1-109.1 = 713 a = F/m = 713/83.8 = 8.51 m/s^2 v = a t h = (1/2) a t^2 25 = (1/2)(8.51) (v/8.51)^2 50 (8.51) = v^2 v = 20.6 m/s
*June 18, 2014*

**math**

well, if sides are both x and the base is 10 then the perimeter is 2 x + 10 so the sides are x, period, no more can be said. If it were equilateral, then every side would be 10
*June 18, 2014*

**math**

sin 20 = w/200 w = 200 sin 20
*June 18, 2014*

**physics**

initial momentum = .0165 * 285 change of momentum = -.0165*285 average speed during stop = 285/2 time to stop = .226/average speed during stop Force = change in momentum / time to stop
*June 18, 2014*

**Physics**

135 min = 2.3 hr speed = (1/2.3) sqrt (105^2+120^2) km/hr velocity = speed at angle tan^-1(120/105) east of north
*June 17, 2014*

**MATH**

well, the easy way is to google Gauss Jordan reduction calculator. http://www.gregthatcher.com/Mathematics/GaussJordan.aspx otherwise do it by elimination First eliminate z from first two: 2x+y-3z = 4 times 2 = 4x+ 2y-6z = 8 4x+0y+2z=10 times 3 = 12x+0y+6z = 30 add the two 16 ...
*June 17, 2014*

**PHYSICS.**

a) m g h / t b) answer to a /.35 is power input that times 3.5 is energy input.
*June 17, 2014*

**Functions**

Good, you are welcome
*June 17, 2014*

**Functions**

180 x - 2 x^2 = A 2 x^2 -180 x = -A x^2 - 90 x = - A/2 x^2 - 90 x + 45^2 = -A/2 + 45^2 (x-45)^2 = -(1/2) (A- 4050) vertex at x = 45 so 45. 45 , 90 area = 4050
*June 17, 2014*

**math**

x^2 - 4 = y x^2 - 4 + (4/2)^2 = y + (4/2)^2 (x-2)^2 = y + 4 so vertex at (2,-4)
*June 17, 2014*

**physics**

-16 + 3 (30)
*June 17, 2014*

**physics**

assuming no friction, gravity does all the work and it is the change in potential energy m g h = 50 * 9.81 * .250 Joules
*June 17, 2014*

**finite math**

5/54
*June 17, 2014*

**Maths**

.7 x = 21 x = 21/.7 = 30
*June 17, 2014*

**math**

.03575/4 = .0089375 per quarter year 30 * 4 = 120 compoundings V = Vi (1.0089375)^120 68,000 = Vi (2.90878 ) Vi = 23,377.45
*June 17, 2014*

**Calculus**

I suppose :)
*June 17, 2014*

**Calculus**

You have dV/dt = k V and you know that k = -.010526
*June 17, 2014*

**Calculus**

sure, in fact I did it with 235 = 240 e^2k
*June 17, 2014*

**Calculus**

dV/dt = k V dV/V = k dt ln V = k t + C e^ln V = V definition of ln V = e^(kt + C) C is arbitrary so far V = e^kt * e^C = C e^kt since e^c could be any old C Now that is general solution. Now put in t = 0 at t = 0 e^kt = e^0 = 1 so 240,000 = C e^0 = C so V = 240,000 e^kt Now if...
*June 17, 2014*

**General Physics 1**

change in velocity/ change in time = (17.9-29.6) / 4.08 = -2.67 m/s^2 d = Vi t - (1/2) 2.67 * t^2 = 29.6(4.08) - 1.33 (4.08^2) = 121 - 22.1 = 98.9 m
*June 16, 2014*

**math**

320 dollars / 40 hours = 8 dollars/hr divide your number line from 0 to 320 up into 40 equal parts.
*June 16, 2014*

**Physics**

695 - 135 = 560 N that is the answer you asked for If you also want the acceleration it is a = F/m = 560/18 = 31.1 m/s^2
*June 16, 2014*

**Physics**

F = m a a = F/m a' = 3 F /2m = (3/2) F/m (3/2)(2) = 3 m/s^2
*June 16, 2014*

**Calculus**

dy / y = 4 e^(5x) dx ln y = (4/5) e^(5x) + c e^ln y = y = e^ [(4/5)e^(5x) +c) y = e^c e^[(4/5)e^(5x) ] y = C e^[(4/5)e^(5x) ]
*June 16, 2014*

**Physics**

change in potential energy = m g h = 12 * 9.81 * 15 = 1766 Joules power = joules per second = 1766/3.5 =505 Watts Input power = 505/.15 = 3363 Watts Input energy = 3363 Watts * 15 seconds = 50,451 Joules
*June 16, 2014*

**Physics**

assume hydrostatics is negligible F = m a a = 200/70 = 2.86 v = Vi - a t 0 = 10 - 2.86 t t = 3.5 seconds to stop d = Vi t - (1/2)(2.86) t^2 d = 10 (3.5) - 1.43 (3.5)^2 d = 35 - 17.5 d = 17.5 meters well, that is what we get. It is ridiculously high but so be it. Let's hope...
*June 16, 2014*

**Physics**

I guess maybe you mean 3.5 kg ??? Force = change in momentum / change in time average speed = (70+0)/2 = 35 m/s so time = .90 /35 = .0257 seconds F = 3.5 * 70 / .0257 = 9528 N
*June 16, 2014*

**physics**

loss of gravitational potential energy = m g * change in height = 5 * 9.81 *(2 + .25) = 110 Joules that is now stored in the spring (1/2)kx^2 so (1/2) k (.25)^2 = 110 k = 3532 N/m
*June 16, 2014*

**Math: Trig**

Perhaps you were supposed to give both the quadrant 2 and quadrant 2 answers
*June 16, 2014*

**Math: Trig**

which is pi +/- pi/3 2 pi/3 or 4 pi/3
*June 16, 2014*

**Math: Trig**

sec = 1/cos so what angle has cosine = -1/2 that angle is 180 + or - 60 degrees
*June 16, 2014*

**college physics**

Archimedes floats boats !!!
*June 16, 2014*

**physics**

I am just plain not going to answer this. Look up what determines the frequency.
*June 16, 2014*

**physics**

Jake, what do you think the answer is? Look at pictures of waves on a string. which is the longest wave? Do waves get longer or shorter as the frequency and number of the harmonic go up?
*June 16, 2014*

**physics**

When you see a (1/2) rho v^2 in something, which principle do you think of?
*June 16, 2014*

**physics**

T = 2 pi sqrt (m/k) 5.5 = 2 pi sqrt (.0029/k) .87535 = sqrt (.0029/k) .766= .0029/k k = .0038 N/m
*June 16, 2014*

**Math**

(sqrt3)/2 / 1/sqrt 3 = 3/2
*June 16, 2014*

**Calculus**

http://www.wolframalpha.com/widget/widgetPopup.jsp?p=v&id=7c9206fea2b96c1f22626b03b18327b3&title=Math+Help+Boards:+Indefinite+Integral+Calculator&theme=blue says: (x-1)/[7 sqrt(x^2-2x+8) ]
*June 16, 2014*

**Calculus**

∫(x2 − 2x + 8)^-1.5 dx
*June 16, 2014*

**Calculus - not sure how but rewrote**

I do not know but suspect you mean ∫1/(x^2 − 2x + 8)^(3/2) dx
*June 16, 2014*

**physics**

101.5 * 10*3 + 1029 *9.81 * 9.5 = 101.5 * 10^3 + 95.898 * 10^3 = 197 k Pa or about 2 atmospheres note, 30 feet deep is about additional atmosphere
*June 15, 2014*

**physics**

x = A sin wt v = A w cos wt a = -A w^2 sin wt = -w^2 x F = m a so -kx = - m w^2 x w^2 = k/m w^2 = k/.0029 w = 18.6 sqrt k when w t = 2 pi, t = T = 5.5 so (18.6 sqrt k) (5.5) = 2 pi sqrt k = .0615 k = .0038
*June 15, 2014*

**physics**

x = .084 sin wt max x = .084 when sin w t = 1 then Pe = (1/2) k x^2 = (1/2) 204)(.084)^2 now what is Ke when sin wt = 1? v = .084 w cos wt if sin wt = 1, then cos wt = 0 because sin^2 + cos^2 = 1 always so v = 0 when sin wt = 1 so TOTAL energy = PE at sin wt = 1 = (1/2) (204...
*June 15, 2014*

**physics**

x = a sin wt v = a w cos wt a = -a w^2 sin wt = -w^2 x F = m a = -kx when x = 0, equilibrium , sin wt = 0 and cos wt is 1. That is max velocity when w t = pi/2, cos wt = 0 so v = 0 v = a w cos wt which is certainly not constant a = -a w^2 sin wt = -w^2 x which is 0 when x = 0 ...
*June 15, 2014*

**physics**

from t = 0 to t = .02 she goes(.21 - .043) = .167 .167 m / .02 seconds = 8.35 m/s
*June 15, 2014*

**english**

multiple sclerosis Is the correct spelling I think.
*June 14, 2014*

**PHYSICS**

calculate distance 20*2 + 40*2 + 60*6 = calculate time 2+2+6 av speed = distance/time
*June 14, 2014*

**Biomechanics**

You exceeded he elastic limit of the material and permanent bending occurred.
*June 14, 2014*

**Algebra**

5*4 the rest cancels.
*June 13, 2014*

**Algebra**

(x-3)(x+5) well, if x were 4 It could be 9 x 1 or if x were 5 it could be 10 x 2 or if x were 6 it could be 11 x 3 or if x were 7 it could be 12 x 4 etc
*June 13, 2014*

**Science**

This question would take all night to answer. I will just make a suggestion or two. Just think about sources. Obviously burning carbon causes CO2 no matter what form the carbon takes (coal, diesel, gasoline, methane ..... ) Some create more problems than others, coal for ...
*June 13, 2014*

**Damon, Still need your help please tho**

You are welcome :)
*June 13, 2014*

**Damon, Still need your help please tho**

y = k/x 4 = k/6 k = 24 so y = 24/x Just do what it says :)
*June 13, 2014*

**Damon, Still need your help please tho**

LOL, many years ago.
*June 13, 2014*

**Damon, Still need your help please tho**

I guess C which is 7; where x =/ 2 assuming that x=/2 means not when x = 2
*June 13, 2014*

**Damon, Still need your help please tho**

7 where x not equal to 2 (x=2 is not in the domain, function undefined there)
*June 13, 2014*

**Damon, Still need your help please tho**

7(x-2) /(x-2) = 7 * 1 = 7 but x may not be 2 or the original denominator would be zero
*June 13, 2014*

**Damon, Still need your help please tho**

did the first one already http://www.jiskha.com/display.cgi?id=1402703533#1402703533.1402705078
*June 13, 2014*

**Algebra ll**

You are welcome.
*June 13, 2014*

**Algebra ll**

x = 3, y = 12 Step 2: Enter the values for your matrix, and press the "Solve" button. Divide row1 by 4 1 -1/2 -3 3 -1 -3 Add (-3 * row1) to row2 1 -1/2 -3 0 1/2 6 Divide row2 by 1/2 1 -1/2 -3 0 1 12 Add (1/2 * row2) to row1 1 0 3 0 1 12
*June 13, 2014*

**Algebra ll**

+4 -2 -12 +3 -1 -3 gauss jordan see http://www.gregthatcher.com/Mathematics/GaussJordan.aspx
*June 13, 2014*

**Tricky Math tho (Damon)**

Yes, C
*June 13, 2014*

**Tricky Math tho (Damon)**

OH !! remainder allowed just do long division 5x - 5 with remainder of 3 so 5x - 5 and 3/(5x-3)
*June 13, 2014*

**Tricky Math tho (Damon)**

try factoring the top. If this problem is possible, a factor is (5x-3) (5x-3)( 5x +or-6 to get 18) (5x-3)(5x-6) hey are you sure it was not 25 x^2 -45 x + 18 ?????
*June 13, 2014*

**Almost done with this math tho**

It is 7 but there is no solution if x = 2 (undefined, zero denominator, not in domain)
*June 13, 2014*

**Almost done with this math tho**

7(x-2) / (x-2) = ?
*June 13, 2014*

**Algebra**

do you mean 1/x + 1/(x+5) + 1/(3x) = 100/225 ???? 225/x +225/(x+5) + 75/(x) = 100 300/x + 225/(x+5) = 100 (x+5)(300) + 225 x = 100x(x+5) 300 x + 1500 + 225 x = 100 x^2 + 500 x 100 x^2 -25 x -1500 = 0 20 x^2 - 5 x - 300 = 0 4 x^2 - x - 60 = 0 (x-4)(x+15) = x = 4 or x = -3.75
*June 13, 2014*

**this math tho (Damon or Steve)**

30 = 5 * 2 * 3 all prime numbers so sqrt (30) is sqrt (30) period however sqrt on the bottom is no fun, should rationalize multiply top and bottom by sqrt 30 (5/sqrt30)(sqrt30/sqrt30) = (5 sqrt 30) /30 = sqrt (30) /6
*June 13, 2014*

**this math tho**

You are welcome :) No thinking, just doing and CHECKING
*June 13, 2014*

**this math tho**

x^2 - 6 x + (6/2)^2 = 7 + (6/2)^2 x^2 - 6 x + 9 = 7 + 9 (x-3)^2 = 16 (x-3) = 4 or (x-3) = -4 x = 7 or x = -1 check 1 + 6 = 7 49 - 42 = 7
*June 13, 2014*

**Another this math tho**

2 * 1 = 2 b^-6 * b^12 = b^(-6+12) = b^6 so yes, 2 b^6
*June 13, 2014*

**this math tho**

well, first of all, check your answer back in the originl for example if x = 8 3 (8-4) + 54 = -3(8) ???? 12 + 54 = -24 I doubt it Now let me try 3 x - 12 + 54 = -3 x 6 x + 42 = 0 x = -42/6 = -7 now check that back in the original
*June 13, 2014*

**ALGERBRA**

that comes out to: .0004952 or use combinations 13 hearts in deck number of combinations of 5 in 13 = c(13,5) = 13!/[ 5!(8!) ] = 1,287 5 in 52 = 52!/[5!(47!)] = 2,598,960 quotient = .0004952
*June 13, 2014*

**ALGERBRA**

first card 1/4 second card 12/51 third card 11/50 fourth card 10/49 fifth card 9/48 multiply :)
*June 13, 2014*

**math**

You are welco0me. Just remember to reverse arrow when multiplying (or dividing) by negative quantity
*June 13, 2014*

**math**

14 < -2x 7 < -x or -7 > x reverse arrow when multiplying by negative quantity or x <-7 check that, for example if x = -8 14 + 7x = 14 - 56 = -42 5 x = -40 so yes, 14 + 7x < 5x
*June 13, 2014*

**Financial Math**

2500 * (1.03^6) = 2985.13 now 2985.13 (1+ .05/12)^24 = 3298.39 3298.39 -2500 = 798.39
*June 13, 2014*

**English**

5 is the only one that sounds right to me.
*June 13, 2014*

**algebra**

look at that second equation. You can easily solve it for y namely y = 2x-1 so use (2x-1) for y in the first equation 3 x - 4(2x-1) = 5 3 x - 8 x + 4 = 5 -5 x = 1 x = -1/5 then y = -2/5 -1 = -7/5 check that -3/5 +28/5 = 25/5 = 5 yes, checks -2/5 + 7/5 = 5/5 = 1, yes, so we ...
*June 13, 2014*

**algebra**

x = 3 , y = 2 is the intersection
*June 13, 2014*

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