Wednesday

July 27, 2016
Total # Posts: 26,563

**physics**

fell distance 4.05 so lost potential energy m g h = 3 * 9.81 * 4.05 That is kinetic energy of bucket plus spool v = omega R = .6 omega call omega = w Ke = (1/2) m v^2 + (1/2)I w^2 = (1/2)v^2 (m + I/.36) I = 5 * .5 * .36 = so I/.36 = 2.5 so 3 * 9.81 * 4.05 = .5 * v^2 *(5.5) ...
*April 6, 2016*

**Physics miscounted**

134.4
*April 6, 2016*

**Physics**

C = Q/v = 40*10^-6 Q = 40 * 10^-6 v i = dQ/dt = 40*10^-6 dv/dt let v = V sin wt dV/dt = V w cos wt so i = 40*10^-6 V w cos w t max i = 40*10^-6 V w w = 2 pi f = 2 pi(60) = 377 so max i = 40*10^-6 * 377 V so V = (2.26/(15080)) 10^6 =1344
*April 6, 2016*

**Math help please**

YOU MEAN sin^2 x=[ 1-cos(2x) ] /2 or 2 sin^2 x = 1 - cos(2x) cos 2 x = cos^2 x - sin^2 x so 2 sin^2 x = 1 - cos^2 x + sin^2 x sin^2 x = 1 - cos^2 x or sin^2 x + cos^2 x = 1 which is true
*April 5, 2016*

**Physics**

620 * .39 = x * 1.53 so (.39/1.53)620
*April 4, 2016*

**Algebra**

maybe you want: 3 7 2 3,7 3,2 7,2
*April 4, 2016*

**English**

Either but I would pick 2 because in the end the person, not the food, is supposed to be healthy.
*April 4, 2016*

**Math**

log3 (3m) log a + log b = log ab That is how a slide rule works. That is how old I am :)
*April 4, 2016*

**PHYSICS!!!**

ke at bottom = (1/2) m v^2 = (1/2) m (144) = 72 m Joules pe at top = m g h= m (9.81)(12.2 sin 18 = 37 m Joules so Lost 72-37 = 35 m Joules to friction Friction force = mu m g cos 18= 9.33 mu m work done by friction = 9.33 mu m * 12.2 = 114 mu m so 35 m = 114 mu m mu = 35/114...
*April 4, 2016*

**PHYSICS!!!!**

10 km/hr = 10/3.6 = 2.78 m/s 3 km/hr = 3/3.6 = .833 m/s 5 km at 10 km/hr --> 30 min which is 30 *60 = 1800 s energy = 700*1800 = 1.26*10^6 Joules 5 km at 3 km/hr --> 6,000 s 6,000 s * 300 w = 1.8*10^6 Joules ==============================
*April 4, 2016*

**Physics**

assuming that your potential energy is defined as zero at the bottom of the hill, all your energy is kinetic by the time you get there. 800 + 200 = 1000 Pert of this problem statement is missing though. In potentials, all you can define is differences. You have to define some ...
*April 4, 2016*

**Math**

2 pi r = 2 pi *7 = 14 pi inches
*April 4, 2016*

**PHYSICS!!**

change in potential energy = m g h = 2219*4*sin 30 = 4438 Joules = (1/2)mv^2 + (1/2)I w^2 but w = v/r = v/.4 = 2.5 v so 4438 = (1/2)(226)v^2 + (1/2)(22.6)(6.25 v^2) or 4438 = 184 v^2 so v = 24.2 m/s and w = 60.4 radians/s Torque * angle = change in Ke T * 2 pi = (1/2) I w^2
*April 4, 2016*

**PHYSICS!!**

first mass of rubber = 2000 * .3 * ∫ 2 pi r dr from r = .2 to r = .4 = 600 (2 pi) (1/2)(.16-.04) = 226 kg 226 * 9.81 = 2219 Newtons weight I = 2000*.3 *∫ 2 pi r^3 dr = 3770 (1/4)(.4^4-.2^4) = 22.6 ===================
*April 4, 2016*

**PHYSICS!!**

time = 100 * 3600 = 3.6 * 10^5 s so energy used= 120*3.6*10^5 = 432 * 10^5 Joules = m g h = 65 * 9.81 * h so h = .677 * 10^5 = 67,700 meters
*April 4, 2016*

**Math**

but 24 inches = 2 feet so r = 1 foot (4/3) pi (1)^3 = 4.19 ft^3 by the way 4/3 x 3.14/1 = 1.395 is wrong --- should be 4.19
*April 4, 2016*

**Math**

3/4 = .75 3/8 = .375 which is bigger?
*April 4, 2016*

**Math**

2(3.14 x 0.25) + 2(3.14)(.5)(4) answer in feet^2
*April 4, 2016*

**no**

You have to use all feet or all inches r = 0.5 feet NOT 6 inches
*April 4, 2016*

**math**

s + (s+30) = 36 2 s = 6 s = 3 f = 33
*April 4, 2016*

**Math-soh cab toa**

sin 30 = h/70 but we all know sin 30 = 1/2 so 35
*April 4, 2016*

**Physics**

final angular momentum about axis of rotation = initial angular momentum initial ang mom = 78*1.6 * 2 = 250 kg m^2/s final ang mom = 78 (2)^2 omega + 651 omega omega ( 963) = 250 omega = .26 radians/second
*April 4, 2016*

**History**

I would have chosen B A ---- interchangeable parts, came before assembly lines for example in weapons manufacture (Colt in Connecticut for example)
*April 4, 2016*

**History**

I suppose I have to agree, but we lost our forests here in Massachusetts to farming and wood stoves long before we had woolen mills and Springfield rifles. The really tall pines of course were marked with broad arrow symbols and reserved for the king's masts.
*April 4, 2016*

**Hard math question**

suspect 1 * 2 * 4 = 8
*April 4, 2016*

**Engineering science**

oh and for time avergae speed = 6/2 = 3 m/s so t = 4/3 seconds
*April 4, 2016*

**Engineering science**

normal force = m g cos 25 friction force = mu m g cos 25 = force down slope = m g sin 25 so sin 25/cos 25 = tan 25 = mu = .466 =================== at 10 degrees friction force = .466 m g cos 10 = .459 m g work done by friction = .459 m g d = loss of kinetic energy = (1/2)m(36...
*April 4, 2016*

**Math**

anything with straight sides and pointy top has volume = (1/3) height * base area so 1/3
*April 3, 2016*

**trigonomentry help!!!**

(x-q)(x-4q) = a x^2 + b x + c x^2 - 5qx + 4 q^2 =a x^2 + bx + c if a = 1 b = -5 q c = 4 q^2 then 4 b^2 = 100 q^2 and 25 a c = 100 q^2 and 100 q^2 -100 q^2 = 0 all right
*April 3, 2016*

**chem**

Mg + 2 HNO3 → Mg(NO3)2 + H2
*April 3, 2016*

**Math**

Perhaps you meant 0.15 % ?????
*April 3, 2016*

**Math**

55 = .15 x x = 366 2/3 which is about 367 :)
*April 3, 2016*

**Geometry**

rectangle is (53 + 6) by (55 + 6) or 59 by 61 2*59 + 2*61
*April 2, 2016*

**algebra**

I gues you are looking for a straight line of slope m = 3 through the point (4,5) y = 3 x + b 5 = 3*4 + b 5 = 12 + b b = -7 so y = 3 x - 7
*April 2, 2016*

**computer science**

I guess I would let n = 0 and y = 0 then I would say n = n+1 y = 12 * n if y > 30 go to the end immediately and stop then I would store and print y go back to that n = n+1 stop and end
*April 2, 2016*

**Math**

e^cos t = value at t - value at pi = value at t - e^cos pi but cos pi = -1 so e^cos t = value at t -e^-1 or e^cos t = value at t - 1/e so value at t = 1/e + e^cos t ------------------- now do value at t - value at 0 value at 0 = 1/e + e^1 = 1/e + e value at t = 1/e + e^cos t ...
*April 1, 2016*

**science**

work done = increase in kinetic energy = (1/2) m (V2^2-V1^2) V2 = 72/3.6 meters/second V1 = 54/3.6 meters/second m = 1500 kg then answer will be in Joules
*March 31, 2016*

**physics**

distance from each = d = sqrt(5^2+12^2) = 13 cm = .13 meter however we may notice that the component along the bisector will be zero due to the opposite signs of the charges. However that is no true of the component along the direction between charges E = k q/.13^2 for each ...
*March 31, 2016*

**Science**

http://en.wikipedia.org/wiki/Electromagnet
*March 31, 2016*

**Science**

the B field strength is proportional to the number of turns.
*March 31, 2016*

**Mathematics**

Looks like a typo problem to me the original was probably round to the nearest thousand dollars, 2000
*March 31, 2016*

**math**

Well done :)
*March 31, 2016*

**math**

Good :)
*March 31, 2016*

**math**

You are welcome, but more importantly do you know how to tell a straight line from a parabola or an exponential now?
*March 31, 2016*

**math**

You typed y = 5x, look up above. I found it correct in one of your earlier postings.
*March 31, 2016*

**AHHH!! NO**

Look, they are asking you which of these is a straight line with constant slope. In other words which looks like Y = m X + b That is B y = 19 x - 10 A, x^2 - 5 x - 14 is a QUADRATIC, parabola C, y = 5^x (NOT y = 5 x ) is exponential D, y = .03 x^2 etc is QUADRQATIC, parabola
*March 31, 2016*

**ah ha - you typed it wrong**

B)y = 19x – 10 C)y = 5^x NOT THIS. This is NOT 5 x as you wrote later.
*March 31, 2016*

**math**

There are two with constant slopes. B and C If you think there is only one answer, you have a typo.
*March 31, 2016*

**math**

B and C 19 and 5
*March 31, 2016*

**College Algebra**

the slope is -29 crimes per year In other words the number of crimes decreases by 29 every year. when t = 0, C = 31,000. That is the number of crimes when the equation started in 1998 I suspect the 31,000 is a typo as is the 29
*March 31, 2016*

**math**

the derivative is constant in B and C
*March 31, 2016*

**Physics**

334 * 2000 = 668,000 J
*March 31, 2016*

**Geometry**

x^2 + 10 x - 1200 = 0 (x-30)(x+40) = 0 x = 30 or x = -40
*March 31, 2016*

**Algebra 2**

3 150 4 150 + d 5 150 + 2 d = 180 so d = 30/2 = 15 month 1 = 150-30 = 120 An = 120 + (n-1)15 A12 = 120 + 11(15) = 285 yes correct 500 = 120 + (n-1)15 n - 1 = 25.33 n = 26.33 yes, 27
*March 31, 2016*

**math**

I guess A is at center and AB bisects CD ???? we need to know angle at center cos (T/2) = 4/5 T/2 = 36.9 degrees T = 73.7 degrees so area = (73.7/360) pi R^2
*March 31, 2016*

**physics**

horizontal speed = u = 50 cos 37 t = 80/u then how high is it at t h = (50 sin 37) t - 4.9 t^2 then d = sqrt (80^2 + h^2)
*March 31, 2016*

**math**

http://davidmlane.com/hyperstat/z_table.html
*March 31, 2016*

**math**

http://davidmlane.com/hyperstat/z_table.html
*March 31, 2016*

**Algebra 2**

d = -27 + 22 = -5 -7 - 5 = -12 -12 - 5 = -17 -17 - 5 = -22 so the last one on the list
*March 31, 2016*

**Math - Slope intercept**

sure looks like it to me. They asked the same question twice. I bet they meant to say: Write the equation in standard form 6 x - 3 y = 2 then solve for y in slope intercept form but who knows
*March 31, 2016*

**luthayi high school. science**

http://www.nlm.nih.gov/medlineplus/ency/article/002680.htm
*March 30, 2016*

**This is a trick question**

Velovicy is a VECTOR north one way, south back 31 lengths, 30 of which were back and forth so went 50 meters total north in the end How long did it take? 31 * 50 = 1550 meters back and forth at 900 m/3600 s time = 1550 *3600/900 = 6200 seconds so 50 meters/6200 seconds = 0....
*March 30, 2016*

**physics**

I will do position last a = dv/dt so a = -10*10^7 t + 3*10^5 zero at t = 3/10 * 10^-2 = .003 seconds a is positive for the whole .003s find v at t = .003 for part c x = integral v dt with x = 0 at t = 0 so x = (1/3)(-5.00×10^7)t^3 +(1/2)(3.00×10^5)t^2 length of ...
*March 30, 2016*

**physic**

k = 20 N/.098 m = 204 N/m m = 20/9.81 = 2.04 kg omega = w = sqrt (k/m) radians/second so w = sqrt (204/2.04) = 10 rad/s if x is distance from equilibrium position, positive up x = -.05 cos 10 t
*March 30, 2016*

**but**

You may not care about order withing each committee so perhaps you mean combinations, not permutations C(8,5) = 8! /[ 5! (8-5)! ] = 8*7*6/[3*2] = 56
*March 29, 2016*

**Geometry**

w L = 500 L = 5 w/4 w(5w/4) = 500 w^2 = 400 w = 20 L = (5/4)20 = 25
*March 28, 2016*

**Physics 110**

well what is the specific heat or heat capacity of water in Joules or Calories (whichever your class is using)per gram (or kilogram or oz or pound) degree centigrade (or Fahrenheit) anyway call it C Heat in = C * 500 (40-10)
*March 28, 2016*

**finance**

EUR = (1.1210/1.125 ) USD but USD = (112.15/114.25 ) JPY so EUR = (1.1210/1.125)(112.15/114.25 ) JPY so EUR/JPY =(1.1210/1.125)(112.15/114.25 )
*March 28, 2016*

**Statistics**

https://www.khanacademy.org/math/probability/statistics-inferential/normal_distribution/v/ck12-org-normal-distribution-problems-empirical-rule but if you really want the right answer to a specific problem without fooling around with 68 - 95 - 99.7 use http://davidmlane.com/...
*March 28, 2016*

**How on earth**

did you get from such a simple first problem to the problem that messes up people who write papers on this sort of thing ?
*March 27, 2016*

**probability**

LOL this is why it is so hard to do this sort of test more positives will be due to that 10% wrong accuracy problem than due to having allergy. out of 1000 people, 10 have allergy out of these 10 who have it .9 * 10 = 9 test positive correctly 1 gets missed out of the 990 who ...
*March 27, 2016*

**Hey, careful !**

first .25^5 = .0009765 NOT what you got This is a BINOMIAL DISTRIBUTION P(5,k) = C(5,k)p^k (1-p)^(5-k) here p = .25 and 1-p = .75 Now the problem 3 right: C(5,3) = 5!/[3! 2!] = 5*4/2=10 P(5,3) = 10 * .25^3*.75^2 = .0879 4 right C(5,4) = 5!/[4! 1!] = 5 P(5,4) = 5 * .25^4 * .75^...
*March 27, 2016*

**physics**

d = Vi t + (1/2) a t^2 Vi = 20 /3.6 = 5.56 m/s V final = 30/3.6 = 8.33 m/s oh well, I do not need the physics equation because Vaverage = (1/2)(5.56+8.33) = 6.94 m/s 6.94 m/s * 20 s = 139 meters
*March 27, 2016*

**Chemistry**

You are welcome.
*March 27, 2016*

**Chemistry**

note expands as pressure goes down and expands as temperature goes up so you can check if you have those ratios right.
*March 27, 2016*

**Chemistry**

T1 = 330 T2 = 380 1.02 * 2.2 / 330 = .789 * V2 /380 V2 = (1.02/.789)(380/330)(2.2) = 3.28 L
*March 27, 2016*

**typo**

P1 V1/T1 = P2 V2/T2
*March 27, 2016*

**Chemistry**

T1 = 57 + 273 T2 = 107 + 273 P1 V1/T1 = P2 V2/T1
*March 27, 2016*

**math**

you ate 4/12 = 1/3 of the area so you ate (1/3) pi (49) 2/3 of the circumference is left (2/3)(pi)(14)
*March 27, 2016*

**math**

sure, why not 12 15/24 6 9/24 5 16/24 ---------- add 23 40/24 well 40 = 24 + 16 so regroup 23 + 24/24 + 16/24 24 + 2/3 because we already know 2/3 = 16/24 24 2/3
*March 27, 2016*

**Are you there?**

It is really important that you get both of my answers.
*March 27, 2016*

**Statistics**

let me do one point so you can see if an error p of 2 right for example P(10,2)= C(10,2) (.25)^2 (.75)^8 but C(10,2) = 10![2! 8!] = 10*9/2 = 45 so P(10,2) = 45 (.0625)(.1) = .282 does that agree ?
*March 27, 2016*

**Statistics**

yes, p = .25 the mean better be ten/4 :) which is 2.5 This is a binomial distribution mean = n p = 10 * .25 = 2.5 (remarkable :) sigma^2 = n p (1-p) =10 (.25)(.75) = 1.875 sigma = sqrt 1.875 = 1.37
*March 27, 2016*

**physics**

v^2/R = 9.24^2/18.4 = 4.64 m/s^2 centripetal acceleration so apparent weight on road = m (g-4.64) = 1800 (9.81 - 4.64) = 9306 N
*March 27, 2016*

**physics**

http://www.jiskha.com/display.cgi?id=1459109572
*March 27, 2016*

**physics**

Tension holds the weight T = 1.3 * 9.81 = 12.75 N The force on the puck is the tension, 12.75 N 12.75 = m v^2/R v^2 = 1.4 * 12.75 /.24 v = 8.63 m/s
*March 27, 2016*

**Algebra**

18 / 8 = 2.25 half lives 1 unit *(1/2)^2.25 = .210 unit left
*March 27, 2016*

**science help PLS**

because the water treatment plant may be taking water from a surface reservoir or be missing contaminants at the well field that are present in your aquifer.
*March 26, 2016*

**science help PLS**

I think A
*March 26, 2016*

**chem**

200 C = 373 K 20 C = 293 K P1 / T1 = P2 / T2 or P2 = P1 T2/T1 = 5.7 (293/373)
*March 26, 2016*

**physics**

x = xo + Vo t + (1/2) a t^2 72 = (1/2) a (36) a = 4 m/s^2 v = Vo + a t at t = 6 v = 0 + 4*6 v = 24 m/s that is initial Vo at 6 if there is no friction, it continues at 24 m/s for 6 s 24 * 6 = 144 m more
*March 26, 2016*

**math**

DRAW IT !!!!! First the triangle on the left (2,3), (8,3), (8,11) base = 6, altitude = 8 so area = 3*8 = 24 Now the right side, the hard part First rectangle (8,3)(8,11)(11,11)(11,3) that area = 3*8 = 24 subtract the triangles top and bottom top is (8,11)(11,7)(11,11) area top...
*March 26, 2016*

**math**

p good = .2 p not good = .8 this is a binomial distribution problem P(n,k) = C(n,k) p^k (1-p)^(n-k) where C(n,k) = n!/[k!(n-k)!] here for example P(10,1) = C(10,1).2^1 .8^9 C(10,1)= 10!/[1(9)!] = 10 so P(10,1) = 10 * .2 * .8^9 = .268 similarly C(10,2) = 10!/[2(8!] = 10*9/2 =45...
*March 26, 2016*

**mathematics**

Oh, I see, it is math, well check physics below.
*March 26, 2016*

**not physics**

We physicists have trouble with this sort of thing. ja + jo = 25 (ja - 8) = 2 (jo-8) ---------------------- well then ja = (25-jo) so (25 - jo - 8) = 2 jo - 16 17 - jo = 2 jo -16 3 jo = 33 jo = 11 I guess ja = 25-11 = 14 then
*March 26, 2016*

**trigonometry**

height + hypotenuse height = 10 tan 60 hypotenus = 10/cos 60 = 20 so 17.32 + 20 = 37.32 meters
*March 26, 2016*

**TRIGONOMETRY**

csc = 1/sin so sin = 1/ csc sin^2 = 1/csc^2 cos^2 = 1 - sin^2 = 1 - 1/csc^2 so tan^2 = sin^2/cos^2 = (1/csc^2)/[1-1/csc^2] tan^2 = 1/[csc^2 - 1] tan = sqrt (1/[csc^2 - 1] )
*March 26, 2016*

**math**

yes = 1.31 / 31200 = 4.2*10^-5 = .000042
*March 26, 2016*

**geometry**

I have no idea what your cone looks like but to find the volume of anything with straight sides and a pointy top multiply the base area by the height and divide by 3
*March 25, 2016*

**physics**

mu * normal force = m g normal force = m omega^2 R so m g = mu m omega^2 R mu = g/(omega^2 R) or as we could have guessed mu = gravity acceleration/centripetal acceleration mu = 9.81/[ 4.2^2 * 3.1 ]
*March 25, 2016*