Thursday

October 8, 2015
Total # Posts: 22,103

**Math**

Altitude h = 12 I think on one side you have a 5, 12, 13 right triangle and on the other a 9 , 12 , 15 right triangle (a 3,4,5 times 3) so average base = (11+25)/2 = 18 altitude = 12 area = 12 * 18
*August 31, 2015*

**Algebra**

agree
*August 31, 2015*

**physics**

The speed is horizontal at the top, call it u and it remains u all the way down because there is no horizontal force (acceleration). So we have a vertical problem first. v = g t h = (1/2) g t^2 so 33.2 = 4.9 t^2 t^2 = 6.77 t = 2.60 seconds so v = 9.81 * 2.6 = 25.5 m/s down ...
*August 31, 2015*

**link better**

http://www.google.com/search?q=hydrogen+radiation+spectrum+transitions&tbm=isch&tbo=u&source=univ&sa=X&ved=0CEwQsARqFQoTCO_83vy_08cCFcgyPgodLu8DCw&biw=1920&bih=971#imgrc=84jXbb3JhPIc3M%3A
*August 31, 2015*

**CHEMISTRY**

Here: https://www.google.com/search?q=hydrogen+radiation+spectrum+transitions&tbm=isch&tbo=u&source=univ&sa=X&ved=0CEwQsARqFQoTCO_83vy_08cCFcgyPgodLu8DCw&biw=1920&bih=971#imgrc=84jXbb3JhPIc3M%3A Look at all possible ways from 4 down to 1 such as 4 - 3 - 2 - 1 or 4 - 2 -1
*August 31, 2015*

**Plus**

10* 569 = 5690 2 * 569 = 1138 add those 12* 569 = 6828
*August 30, 2015*

**Math**

10 * 20 * 500 = 200 * (1,000/2 ) = 100 * 1,000 = 100,000
*August 30, 2015*

**Science - physics**

average speed during stop = 122/2 = 61 m/s to get time to stop v = 0 = 122 - 6.2 t t = 122/6.2 = 19.7 seconds so distance = v average * t = 61*19.7 = 1200 meters Off the end of the runway and 200 meters into the bleak ocean
*August 30, 2015*

**Calculus**

f' = sec x tan x + 2 sin x at x = pi/3 which is 60 deg f' = m = (2 * sqrt 3) + 2 (sqrt 3/2) so m = 3 sqrt 3 so y = 3 sqrt 3 * x + b at (pi/3 , 1) 1 = 3 (pi/3) sqrt 3 + b b = 1 - pi sqrt 3 so y = (3 sqrt 3) x + (1-pi sqrt 3) or approx y = 5.20 x - 4.44
*August 30, 2015*

**Calculus**

nothing wrong with that
*August 30, 2015*

**MATH ALGEBRA**

x = number of trees at year n at year 0, x0 = 7000 at year 1, x1 =.88*X0 + 600 = 6160+600 = 6760 at year 2, x2 = .88*x1 +600 = 6548.8 at year 3 , x3 = .88x2+600 = 6362.9 at year 4, x4 = .88*x3 + 600 = 6199.4 at year 5, x5 = .88*x4+600 = 6055.5 at year 6, x6 = .88*x5+600 = 5928...
*August 30, 2015*

**math calculus**

typo in second line .7 = e^-40 k
*August 30, 2015*

**math calculus**

a = A e^-kt .3 = e^-40 k ln .7 = -.357 = -40 k k = .008917 so 1/2 = e^-.008917 t if t is half life ln .5 = - .693 = -.008917 t t = 77.7 hours
*August 30, 2015*

**math**

Been there, done that: http://www.jiskha.com/display.cgi?id=1440890314
*August 30, 2015*

**Calculus**

If this is y = [ x^4 + x ]^.5 ?????? dy/dx = .5 [ x^4 + x ]^-.5 (4x^3 +1) = .5 (4x^3+1) /sqrt(x^4+x) ================================= if you mean y =( x^.5 )(x^3+1) y = x^3.5 + x^.5 dy/dx = 3.5 x^2.5 + .5 x^.5 /x = x^.5 ( 7 x^2 + 1/x)/2 = x^.5 (7 x^3 + 1) /(2 x) = (7 x^3 + 1...
*August 29, 2015*

**Physics**

Bug dv/dt = ab = 60 mi/h/2.4s = 25 mi/(s h) = 40.2 km /(3600 s^2) Sal dv/dt = as = 60/2.8 = 21.4 mi/(s h) =34.4 km/3600s^2 v = 75 km/h = 75 km/3600s then v = a t or t = v/a Bug: t = 75 km/3600 s / 40.2 km/3600s^2 = 1.87 seconds d = (1/2) a t^2 = OR use half max (average) speed...
*August 29, 2015*

**SCIENCE!**

1. - Did the rock chip hit him in the eye? 2. what mistake did Andrew make using measurement units? for density he needs VOLUME, not distance. He measured centimeters. He needs centimeters CUBED or cm^3 or cc 3. yes, write it in your lab notebook ! 4. I think he determined the...
*August 29, 2015*

**math**

I will try to reverse engineer what you are doing because I am not sure I understand you Say we are doing a compound interest problem. Yearly interest rate as a decimal is r For example 5% is .05 then every year I multiply what I have is the amount from the year before + r ...
*August 29, 2015*

**Math**

s^2 + 1 = (1/2)(4s) s^2 - 2 s + 1 = 0 (s-1)(s-1) = 0 s = 1
*August 29, 2015*

**math**

for exponential growth (continuous compounding) amount = original * e^rt rate = -.02 or -2 percent for example if you have ten dollars then after one year you will have 10 e^-.02 = 10(.980298) = nine dollars and eighty cents so each year multiply by .98 NOT 1.98 BUT that is an...
*August 29, 2015*

**Geometry**

5p^2-23p+24 well 24 = 4*6 or 3*8 or 2*12 or 1*24 so what might work in ( 5 p - %%) (p - %%) 15 and 8 is 23 so try 3*5 and 8 (5 p - 8)( p - 3 )
*August 29, 2015*

**math**

r = 0.06 meters A = pi r^2 F = 350,000 Newtons p = F/A = 350,000 /(pi *.06^2) in Newtons per square meter which is Pascals
*August 29, 2015*

**pre-calculus**

1) if it is really 4x = 3 then x = 3/4 a vertical line 2) 9y - 7 - 3y = 0 6 y = 7 y = 7/6 a horizontal line of slope 0 3) 7 x + 2 y = 14 2 y - -7 x + 14 y = -(7/2) x + 7
*August 29, 2015*

**integral calculus**

hmmm, graph that first function. sin a cos b = (1/2)sin(a+b)+(1/2) sin(a-b) (remember about beat frequencies :) so (1/2)[ sin(5x) dx - sin(x) dx ] ok? ======================================= let y = 3x then dy = 3 dx or dx = (1/3) dy so (5/3) [ cos^2 y dy ]
*August 29, 2015*

**Science**

agree
*August 29, 2015*

**Physics**

m = F/a
*August 29, 2015*

**Physics**

2*3600 seconds/h = 7200 seconds 75 * 7200 = 540,000 Joules total electricity use .7 * 540,000 = heat Joules .3 * 540,000 = light Joules
*August 29, 2015*

**Math**

x y = 15876 y = 9 x so 9 x^2 = 15876 x^2 = 1764 x = 42 =================== 169 + x^2 = 794 x^2 = 625 x = 25
*August 29, 2015*

**Chemistry**

150.01 - 104.70 = 45.31 grams of syrup .140 pint = 66.2 mL true so density = 45.31 grams/66.2 mL = 0.684 grams/mL = 0.684 grams/cubic centimeter
*August 29, 2015*

**physics**

work done on metal = m g h = .411*9.81*5.22 = 21.05 Joules 21.05 = .344 ke of hammer so ke of hammer = 61.2 Joulesd (1/2) 8.46 v^2 = 61.2 v^2 = 14.5 v = 3.80 m/s
*August 29, 2015*

**physics**

find bullet momentum from conservation of momentum .05 v = .55 * 4 = 2.2 then 2 V + 2.2 = 0 V = -2.2/2
*August 28, 2015*

**physics**

1.5*10^-4 = (1/2) (2.4*10^-4) v^2 so v^2 = 3/2.4 = 1.25 v = 1.11 m/s
*August 28, 2015*

**physics**

at takeoff Ke = (1/2) m v^2 = 1.5*10^-4 solve that for v work done = force * distance 1.5*10^-4 = .42 * distance
*August 28, 2015*

**physics**

change in potential energy = m g h the gravitation force is opposite to the direction of motion so work done = -m g h the escalator force is in the direction of motion so work done by it is +m g h
*August 28, 2015*

**physics**

Q = flow rate = speed * area 43 pi R^2 = n * .066 pi r^2
*August 28, 2015*

**physics**

delta p = rho g delta h 35*10^3 = 1025 *9.81 * h h = 3.48 meters
*August 28, 2015*

**physics**

hey, I did the one about the eardrums.
*August 28, 2015*

**physics**

k x = 250 = 510 x so x = 250/510
*August 28, 2015*

**physics**

power = work/time = F * d /t so 50.2 = F * 1.17 / 1.84 = 78.9 N agree
*August 28, 2015*

**Physics**

v = a t
*August 28, 2015*

**Idk**

tow means two? 2.5/3 = .8333333333333333333333333333
*August 27, 2015*

**Geometry**

Draw it 5x-3 + x-9 = 5 x -12 + x = 0 x = 12 HJ = 5(12)-3 = 57 JK = x-9 = 3
*August 27, 2015*

**Math**

Look 8^1 = 8 8^2 = 8*8 = 64 8^3 = 8*8*8 = 64 * 8 = 512 8^4 = 8*8*8*8 = 512 * 8 = 4096 8^5 = 4096*8 = 32768
*August 27, 2015*

**Math**

8*8 = 64 64*8 = 512
*August 27, 2015*

**Algebra**

76-12 = 64 for n = 2 108-76 = 32 for n = 3 124 -108 = 16 132 - 124 = 8 136 - 132 = 4 138 - 136 = 2 139 -138 = 1 139.5- 139 = .5 Yn+1 - Yn = 64/2^(n-1) or Y1 = 12 Yn+1 = Yn + 64/2^(n+1)
*August 27, 2015*

**Physics**

V = pi (5)^2 * 15 m/V = 1.3 so in grams m = 1.3 V divide by 1000 to get kg
*August 27, 2015*

**Geometry check**

You are welcome.
*August 27, 2015*

**Geometry check**

You are not stuck, you are doing fine. Yes (1/2) * (1/2) = 1/4 :)
*August 27, 2015*

**Geometry check**

Yes, I agree with you.
*August 27, 2015*

**math**

.8*7.95 = $ 6.36
*August 27, 2015*

**Equation**

x^2 - b x + (b - 1) = 0 x = [ b +/- sqrt (b^2 - 4b+4 ) ]/2
*August 27, 2015*

**Computer**

Word is a software program.
*August 27, 2015*

**Math**

An infinite number of them. What are your choices?
*August 26, 2015*

**Algebra**

20.00 - 3.00 x
*August 25, 2015*

**College Physics**

get t from v = a t then get d from d = (1/2) a t^2
*August 25, 2015*

**Math**

You do not even need the trig formulas for this because if sin A = .5 then in the first quadrant A = 30 degrees so 2A = 60 degrees cos 60 = 1/2 sin 60 = (1/2)sqrt 3
*August 24, 2015*

**math**

let u = 1/x let v = 1/y 5 3 |u| 19 2 1 |v| 7 D = 5*1-3*2 = 5-6 = -1 Du = 19*1-3*7 = 19-21 = -2 Dv = 5*7-19*2 = 35-38 = -3 then u = Du/D = -2/-1 = 2 so x = 1/u = 1/2 and v = Dv/D = -3/-1 = 3 so y = 1/3 You have typos I think I assume the second one is actually log x + 2 log y...
*August 23, 2015*

**Math typo I think**

7,361,920,000 * 1.0114
*August 23, 2015*

**calculus**

assume n is constant in general: d/dx a^u = a^u * ln a * du/dx so dy/dx = 2^nx * ln 2 * n
*August 23, 2015*

**alGEBRA 1**

12 *1.03 = 12.36 highest 12 * .97 = 11.64 lowest -------------------------subtract range = .72 from lowest to highest
*August 23, 2015*

**Economics**

if your currency is weak, travel to a strong currency place becomes expensive. weak rand and strong dollar ----> fewer dollars per rand which means more rands per cup of coffee in New York.
*August 23, 2015*

**Calculus**

f+dx = 2(x+dx) - 5 = 2 x + 2 dx -5 f(x) = 2 x - 5 ((f(x+dx) - f(x)) = 2 dx divide by dx = 2 no need to approach 0 with this, the slope of a straight line is constant. by the way the derivative of 2 x - 5 is 2
*August 23, 2015*

**Math**

37 - 19 if all in a row.
*August 22, 2015*

**statistics**

http://davidmlane.com/hyperstat/z_table.html
*August 22, 2015*

**physics**

v = a t
*August 22, 2015*

**physics**

since the was no change in direction, the speed is the magnitude of the velocity with no directions specified. ( poor wording of question, velocity is a vector with magnitude and DIRECTION. Speed is just a scalar. For speed use a speedometer. For velocity you need the ...
*August 21, 2015*

**physics**

figure out how long the whole trip took t = 11.2/52 + 23.2/40 + 48.2/31.9 and how many miles total? d = 11.2 + 23.2 + 48.2 then average speed = d/t
*August 21, 2015*

**Geometry**

difference in x = (7-1) = 6 difference in y = (-7 -1) = -8 hypotenuse = distance = sqrt(36+64) = 10
*August 21, 2015*

**Algebra**

x^5/2 * x^-3/2 = x^1 = x 5^-1/2 * 5^1 * 5^-3/2 = 5^-1 =1/5 x/5
*August 21, 2015*

**Dimensional Analysis Chemistry**

You are welcome :)
*August 19, 2015*

**Dimensional Analysis Chemistry**

ppm = M * molar mass * 1,000 = 2.1*10^-9 * 207.2 * 10^3 = 435*10^-6 = 4.35 * 10^-4 ppm Agree with you however would there not be more parts per billion than parts per million? 1 ppm = 10^3 ppb so 4.35 * 10^-1 ppb
*August 19, 2015*

**Calculus**

do you know that sin x ---> x as x --->0 ? if not I will show below given that sin x --> x we have 3x/x = 3 ===================== series for sin x sin x = x - x^3/3! + x^5/5! .... as x --0 sin x --> x - much smaller stuff
*August 19, 2015*

**Algebra 2**

this is an arithmetic series with a = 500 d = 10 look at https://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html
*August 19, 2015*

**Math**

A2 = 180 - A1 A2 = 180 - 115 = 65 because they are supplements 90 - 65 = 25 because complements add to 90 degrees
*August 19, 2015*

**math**

You are welcome :)
*August 19, 2015*

**math**

put a line through A and B slope = 9/3 = 3 2 = 3 (0) + b y = 3 x + 2 now c 15 = 3*5+2 no, oh dear then D 23 = 3*7 + 2 yes and E 3x+2 = 3 x + 2 yes So C is no good, invalid, evil, boil in oil
*August 19, 2015*

**G ss jikowyi subject physics**

Thank you Lori. That saves me some time.
*August 19, 2015*

**Social studies.**

Probably A is correct.
*August 18, 2015*

**MATH**

12*4/5 = 12/1 * 4/5 = 12*4 / 1*5 = 48/5 = 9 3/5
*August 18, 2015*

**physics**

pressure * one tire area = (717+80)/2
*August 16, 2015*

**Physical science**

Sorry, ball E both has no charge and a positive charge. I can not make sense of this or I would have replied long ago. It is either as typo or an error or I am simply not understanding. if the rod attracts E , E is + B is - so D is + so D would repel E Repel and no effect is a...
*August 15, 2015*

**Urgent math**

look up binomial expansion (p+q)^n = p^n + C(n,1) p^(n-1)q^1 ... etc where c(n,m) = n!/[(n-m)! m!] for n = 5 the coefs are 1 5 10 10 5 1 so 32x^5 + 5*16x^4*y^2 ...... y^10
*August 15, 2015*

**pre-calculus urgent**

a(n) = a(n-1)r [a(n)]^2 = [a(n-1)r]^2 = [a(n-1)]^2 r^2 so common ratio is r^2 instead of r
*August 15, 2015*

**pre-calculus urgent**

a(n) = a(1) + (n-1) d a(10) = 2 = 6 + 9 d -4 = 9 d d = -4/9
*August 15, 2015*

**Math**

first term = 1/3 term(n+1) = (2/3) term(n) geometric sequence with a = 1/3 and r = 2/3 look here: http://www.mathsisfun.com/algebra/sequences-sums-geometric.html
*August 15, 2015*

**Algebra 1**

This makes little sense but anyway: c^2 - 10 c + 16 = - p c^2 - 10 c = - p - 16 c^2 - 10 c + 25 = -p + 9 (c-5)^2 = - (p-9) max at c = 5 and p = 9
*August 14, 2015*

**Physics**

20^3 = 2^3 * 10^3 = 8,000 6.5 g/cm^3 * 8,000 cm^3 = 52,000grams = 52 Kg 1300g * (1 cm^3/6.5g) = 200 cm^3
*August 14, 2015*

**Pre-Calculus**

3000 = 675 + .11 (s-1900) 2325 = .11 s - 209 .11 s = 2534 s = 23036.36
*August 14, 2015*

**afrikaans (AFK503/101)**

niets te danke :)
*August 12, 2015*

**afrikaans (AFK503/101)**

Oh my: I see the following: 11.5.4 Afrikaans is nie my moedertaal nie. Mag ek die werkopdragte en die eksamenvraestel inEngels beantwoord? AFK1053 is ‘n module wat gemik is op die verbetering van studente se Afrikaanse taalvaardighedeten opsigte van lees, luister, ...
*August 12, 2015*

**afrikaans (AFK503/101)**

Kommunikasiegapings = gaps in communication flaaitaal = street talk (Vlaai is a baked good in the Netherlands)
*August 12, 2015*

**Mathematical Economics and Linear Programming**

[ bottom d top/dx - top d bottom/dx]/bottom^2 [(cx+d)(2ax) - (ax^2+b)(c)] /(cx+d)^2 agree = [2acx^2+2adx - acx^2-bc] /(cx+d)^2 disagree sign of bc = [acx^2 + 2adx - bc ] /(cx+d)^2
*August 12, 2015*

**Algebra ASAP**

yes for n=1 3^2 -1 = 8 3^2(n+1) - 1 = 3^2n * 3^2 - 1 so 3^2(n+1) - 1 = 3^2n * 9 -1 = 3^2n * 8 + 3^2n-1 = 8 times something + the one before
*August 12, 2015*

**Physical Science- Atomic Structure**

What goes in comes out.
*August 12, 2015*

**Physics**

I think that is the altitude, not the radius. Use 26,199 mi
*August 11, 2015*

**Physics**

iniitial angular momentum about hinge = m v r = .010 *400 * 1 = 4 kg m^2/s or omega = v/r = 400/1 I = m r^2 = .010 (1)^2) so I omega = .01 * 400 = 4 agains now final angular momentum is the same I = .010 *1^2 + (1/3)(10)1^2 = .01 + 10/3 = 3.34 kg m^2 so I omega = 4 = 3.34 ...
*August 11, 2015*

**Physics**

I guess the moment or inertia is 1/3 of original If I w is constant then w' = 3 w then if original Ke = (1/2) I w^2 the final is (1/2)(I/3)(9w^2) = 3 times original has to do work to pull mass in toward the axis of rotation against centripetal force.
*August 11, 2015*

**physics**

specific r double ---> double r diameter doubles --> resistance 1/4 lenght * 3 ----> r *3 2/4*3 = 3/2 3/2 * 2 ohms = 3 ohms
*August 11, 2015*

**calculus**

Its slope is the same as of y = -6x+6 or slope = -6 at (1,0) so do it just like I did the other one.
*August 10, 2015*