Monday

October 24, 2016
Total # Posts: 27,530

**URGENT! Due soon and I used 8 of 10 attempts**

.145 = (1/2)^n log .145 = n log .5 n = 2.786 half lives 2.786 * 5730 = 15963 = 1.5963*10^4 years

*February 14, 2016*

**precalc11**

check 700 * 1.0356^30 = 1999.99

*February 14, 2016*

**precalc11**

2000 = 700 x^(2000-1970) 2.857 = x^30 log 2.857 = 30 log x log x = .0151977 x = 1.0356 so 3.56 percent per year

*February 14, 2016*

**Physics**

total mass = 8.10+3.90 = 12.0 kg gravitational force = 3.90*9.81 = 38.3 N f = m a so a = 38.3/12 = 3.19 m/s^2 the 38.3 - T = 3.90 a = 3.90(3.19) T = 38.3 - 12.4 = 25.9 Newtons

*February 14, 2016*

**Physical science**

G = 6.67 * 10^-11 so 6.67*10^-11 * 1215^2 /(31)^2

*February 14, 2016*

**Physical science**

G M1 M2 /d^2

*February 14, 2016*

**MATH**

well, I guess we could use 6 - 2x for y 3 x + 2 (6-2x) = 6 3 x -4 x + 12 = 6 x = 6 then y = 6 - 2(6) = -6

*February 14, 2016*

**Chemistry**

HNO3/CU(NO3)2 = 4 mols /1 mol so 6/x = 4/1 4 x = 6 x = 1.5

*February 14, 2016*

**Math**

if x>/=0, y = 2-2e^-x if x <2, y = -1

*February 14, 2016*

**science chemistry**

note, absorbed high energy radiated much lower energy therefore, energy of atom went up.

*February 13, 2016*

**science chemistry**

http://www.jiskha.com/display.cgi?id=1455410600

*February 13, 2016*

**science chemistry**

Now I just did one using the same relationships between frequency, period, speed of light, wavelength and energy. This one is the same.

*February 13, 2016*

**Chemistry**

E = h f 3.2 * 10^-19 = 6.6*10^-34 f f = .485 * 10^15 Hz T = 1/f = 2.06 * 10-15 seconds if c = 3*10^8 m/s lambda =c T =3*10^8 * 2.06*10^-15 = 6.19 * 10^-7 meters = 619 * 10^-9 meters

*February 13, 2016*

**math**

Tara, the legs are 90 degrees from each other

*February 13, 2016*

**math**

north 55*3 west 65 * 3 hypotenuse = 3 sqrt (65^2+55^2)

*February 13, 2016*

**Chem**

4 mols of NH3 for every 3 of O2 so 4 4/3 = 8/6 so 6 of O2 also 4/2 = 8/4 so 4 of N2 4/6 = 8/12 so 12 of H2O I am getting bored :( 4/2 = 2/1 so 2 of NH3 3 of H2O enough already

*February 13, 2016*

**physics**

LOL, well we all know that pressure is density * v^2 but we better answer the question anyway. pressure = force/area = mass * acceleration / area^2 = M L/T^2 / L^2 = M /(L T^2) density = M/L^3 velocity = L/T so density * velocity^2 = M/L^3 *L^2/T^2 = M (L T^2) which sure ...

*February 13, 2016*

**Physics**

Google "Lagrange point"

*February 13, 2016*

**MATH>:(**

space 1, any of 7 space 2, any of 6 space 3, any of 5 etc 7! = 7*6*5*4*3*2*1 = 5040

*February 11, 2016*

**Pre-Calc**

(x+a)(x+a) x = -a or x = -a :) -a,-a (-a)^2 + 2a(-a) + a^2 a^2 - 2 a^2 + a^2 = 0 would you believe?

*February 11, 2016*

**Math**

height = 4 cm length = width = x-8 (x-8)(x-8)4 = 324 x^2 -16 x + 64 = 81 x^2 - 16 x - 17 = 0 (x-17)(x+1) = 0 well it is not -1 so x = 17 17 by 17

*February 11, 2016*

**been there, done that**

did that above

*February 11, 2016*

**Linear Algebra**

Here you go: http://en.wikipedia.org/wiki/Linear_algebra

*February 11, 2016*

**Linear Algebra**

By the way , that is algebra, and it is linear, but it is not "linear algebra" Google "linear algebra " :)

*February 11, 2016*

**Linear Algebra**

(Y2-Y1)/(X2-X1) = (1+3) /(1+2) = 4/3

*February 11, 2016*

**Linear Algebra 8; Slope-Intercept Form**

Now that was not even linear, never mind linear algebra LOL

*February 11, 2016*

**Linear Algebra 8; Slope-Intercept Form**

7^2 + x^2 = 11^2 49 + x^2 = 121 x^2 = 72 = 36 * 2 x = 6 sqrt 2 = 8.48528 which is around 8.5

*February 11, 2016*

**General physics**

x direction Fx = 2.8 + 4 = 6.8 Fy = -3.5 - 11.5 = - 15 Ax = 6.8/4.6 Ay = -15/4.6 |A| = sqrt (Ax^2 + Ay^2)

*February 10, 2016*

**Math**

well, it looks like y depends on x so if x = 6 then y = 60 - 3

*February 10, 2016*

**algebra**

Anyway, my way is more fun !

*February 10, 2016*

**algebra**

I GET x^2 + 6 x -7 facor that (x+7)(x-1) so -7 and 1 the end finally

*February 10, 2016*

**algebra**

I get (x-2)(x^3 + 8 x^2 + 5 x - 14) now 14 is either 14 and 1 or 7 and 2 2 does not work this time :( try -2 -8 + 32 -10 - 14 =-24+24 = 0 CARAMBA !!! X = -2 IS A SOLUTION SO (x+2)(x-2) so far divide x^3+8x^2+5x-14 by (x+2)

*February 10, 2016*

**algebra**

well, 28 has to have factors 2 14 4 7 lets try 2 and -2 16 + 48 -44 - 48 +28 lo and behold = 0 so x = 2 is a solution and (x-2) is a factor so divide that mess by (x-2) I get with long division (to be continued :)

*February 10, 2016*

**alebra**

This is a circle x^2 + 8 x + 16 + y^2 -8y +16 = 49+32 = 81 = 9^2 (x+4)^2 + (y-4)^2 = 9^2 center at x = -4 , y = +4 , radius 9 sketch it Now do the problem when x = 0 y^2 - 8 y - 49 = 0 y = [ 8 +/- sqrt (64+196) ]/2 y = 4 (of course) +/- 6.32 when y = 0 x^2 + 8 x - 49 = 0 x...

*February 10, 2016*

**Algebra 2**

LOL 90 + 45 + other angle = 180 so other angle = 45 In other words we know from the start that it is an isoceles right triangle. sides are 8 hypotenuse is 8 sqrt 2 because 1^2 + 1^2 = 2^2 :)

*February 10, 2016*

**Math**

A and A-2 A + A - 2 = 24 2 A = 26 A = 13 B = 11

*February 10, 2016*

**Physics**

I asks where the potential is zero, not necessarily where the force is zero You can add the potential due to the two charges on the x axis V = k Q/R1 = k Q1 /|x-xq| forget k and the 10^-6 because they are the same for both and we are looking for zero I will do the - 2 first -2...

*February 9, 2016*

**Spelling**

Now Rahul, do you get that (a^2-b^2) = (a+b)(a-b)

*February 9, 2016*

**Spelling**

ROTFL How can you make a cohesive sentence using the word cohesive? IS one :) I am not sure about the Elmer's sentence, would have used "adhesive". However the cohesive group works.

*February 9, 2016*

**Algebra**

what you are missing is a rule to remember a^2-b^2 = (a+b)(a-b)

*February 9, 2016*

**Algebra**

(x^2-a^2)/(x-a) = (x-a)(x+a) /(x-a) = (x+a)

*February 9, 2016*

**Algebra**

x^2 - a^2 = x^2 - a^2 (x-a)^2 = x^2 - 2 a x + a^2 quite a different animal

*February 9, 2016*

**math**

-4^.000001 = -1.000001386 :) it really means - (4)^0

*February 9, 2016*

**physics**

Tension = T T sin 20 = weight = m g so T = m g/sin 20 = 28.7 * m if g = 9.81 m v^2/R = T cos 20 = 28.7 m (.94) so v^2/R = 27 v^2 = 27 R R = 1.5 cos 20 = 1.41 meter so v^2 = 27(1.41) v = 6.17 m/s circumference = 2 pi R = 8.86 meters time around = 8.86 meters/6.17 m/s = 1.44 ...

*February 9, 2016*

**Math**

term n = 32 (1.5)^(n-1) when n = 1 term 1 = 32 (1.5)^(1-1) = 32(1.5)^0 but anything^0 = 1 so first term is 32 when n-1 = 0 32 48 72 108 162 243 364.5 546.75 etc

*February 9, 2016*

**Math**

48 - 32 = 16 = d 108 - 72 = 36 = d d is NOT CONSTANT SO NOT arithmetic !!!!!!! but 48/32 = 1.5 = r 108/72 = 1.5 = r SUCCESS ! r, the ratio, is 1.5, GEOMETRIC

*February 9, 2016*

**Physics**

m g h = 981 Joules 245 Joules is lost heating the pavement 981 - 245 = 736 Joules is left at the bottom That 736 Joules is all Kinetic Energy now because m g h = m g * 0 = 0 245 Joules was lost. I do not know the time so can not tell you the rate of energy loss (power) ...

*February 9, 2016*

**physics**

E dot A = 3640 * .166 * .72 = yes, 435 N m^2 /C If the plane is turned 90 degrees, none of the E field goes through it. E dot A = 0 The answer is ZERO

*February 9, 2016*

**Algebra**

Huh? They are all the same.

*February 9, 2016*

**math, ratios**

the number of pairs of shoes to number of shoes is 1/2 I can trade 29 dofrangles for every 30 fringbats. These are adjacent country currencies on the island of Qfrink. In fact I can get one dollar for every 29 dofrangles and one dollar for every 30 fringbats. there are 52 ...

*February 9, 2016*

**Chemistry**

Well, you can find the electric field E due to charge 1 at charge 2, then multiply that field by charge 2 to find the repulsive force (note, same sign charge repels, different signs attract) HOWEVER, normally you use Coulombs Law F = k Q1 Q2 / r^2 ( Google "Coulomb's ...

*February 9, 2016*

**Chemistry**

I guess that is CuC2 hydrated with x H2O CuC2 = 63.5 + 24 = 87.5 grams/mol so 1.6045 grams * 1 mol/87.5 grams = .0183 mol of CuC2 H2O = 18 grams/mol we have how many mols of H2O? 1.9045 - 1.6045 = 0.3 grams H2O so 0.3 / 18 = .01667 mol H2O looks like about as many mols of H2O ...

*February 9, 2016*

**pysics**

force times distance in the direction of the force = 20 N * 1 meter = 20 Joules

*February 9, 2016*

**physics**

omega = sqrt (k/m) = sqrt (12.6/.0107) = 34.3 radians/s x = .378 cos (omega t) v = -.378(34.3) sin (omega t) when x = .378/2 cos(omega t) = .5 then omega t = 60 degrees = pi/3 radians then sin (omega t) = .866 (I am ignoring signs here, we need speed not velocity) v = .378 * ...

*February 9, 2016*

**Physics**

positive v from 0 to 2 negative v from 2 to 5 positive v from 5 to infinity parabola holds water, crosses below x axis between 2 and 5 vertex at t = 3.5

*February 9, 2016*

**Physics**

ans part 3 is from - 30 to + 2 = +32

*February 9, 2016*

**Physics no part 4**

part 4 use absolute value of distance is 52 + 20 = 72

*February 9, 2016*

**Physics**

I assume that we do not do negative time so v is positive for 0<t<2 and for t >5 when t = 0, x = -30 when t = 2, x = 22 when t = 4, x = 2 so 28 from 0 to 4 (part 3)agree part 4 +52-20 = 32

*February 9, 2016*

**Physics**

dx/dt = 6 t^2 - 42 t + 60 = 6 (t^2 - 7 t + 10) = 6 (t-2)(t-5) negative from 2 to 5 (Not 3 to 5)

*February 9, 2016*

**Calculus**

c = cups/day p = pennies/cup dc/dp = -2/5 so c = -(2/5) p + constant when p = 50, c = 40 so 40 = -2*50/5 + constant constant = 60 and c = -(2/5) p + 60 now you can make that p = 5n if you choose where n is an integer number of nickels c = -2 n + 60

*February 8, 2016*

**physics**

Now I did the grasshopper, same deal

*February 8, 2016*

**physics**

h = Vi t - 4.9 t^2 .587 = Vi t - .5*9.81 t^2 but t at top is Vi/9.81 where 0 = Vi - g t .587 = Vi^2/9.81 - .5 * 9.81 (Vi^2/9.81^2) .587 = .5 * Vi^2/9.81 Vi = 3.39 m/s vertical up Vi = speed * sin 58 so speed = 4.00 m/s part a u = 4.00 cos 58 = 2.12 m/s time in air = 2 * rise ...

*February 8, 2016*

**Math**

out of n, n-6 were gotten right so let's find n-6 Jack alone got 40 -32 = 8 Jill alone got 50-32 = 18 so in total alone they got 26 plus they got 32 together 26 + 32 = 58 right total plus the 6 wrong = 64

*February 8, 2016*

**maths**

every year multiply value by 0.90 1 year= 20,000 * .9 2 years 20,000 * .9^2 3 years 20,000 * .9^3 so part (c) n years 20,000 * .9^n It is like reverse compound interest, it will not go down 2,000 every year, but only 10% of its MOST RECENT value every year so 2 years 20,000...

*February 8, 2016*

**History**

Hey, that is pretty good. I am not a fan of his mother though.

*February 8, 2016*

**physics**

v at 10 m/s at t = 0 a = (final velocity-initial velocity)/time = (20 - 10)/5 = 2 m/s^2 so from (0,10) slope up = 2 m/s^2 to (5,20) from (5,20) to (25,20) horizontal from (25,20) to (35, 0 ) straight slope down (slope = -2)

*February 8, 2016*

**physics**

a = (final velocity -initial velocity)/time a = 49/16 m/s^2 weight = m g + m(49/16)

*February 8, 2016*

**maths**

looks like arithmetic sequence a = 3 d = 2 however sum of what terms?

*February 8, 2016*

**Physics**

now do A = F/m

*February 8, 2016*

**Physics**

Its acceleration will be in the direction of the net force Force horizontal component= Fh = 6.6*10^6 cos 47.5 Force vertical component = Fv = 6.6*10^6 sin 47.5 - 4.5*10^5*9.81 so Fh = 4.46*10^6 N Fv = 2.19*10^6 N F = sqrt(Fh^2+Fv^2) = 4.97*10^6 N tan A = Fv/Fh = 2.19/4.46

*February 8, 2016*

**Science**

eg: http://en.wikipedia.org/wiki/Lunar_mare

*February 8, 2016*

**Science**

1 a yes 2 b yes 3 a no b 4 c no d usually moon blocks sun light 5 a no c 6 d no b 7 a no c 8 b no a it all hits the other side 9 d no b 10 Google !!!! Hey - get yourself a light and a tennis ball and a soccer ball !

*February 8, 2016*

**Math Questions**

You are welcome.

*February 8, 2016*

**Math Questions**

2(9/3) = 2(3) = 6 yes 1 (18/6) = 1(3) = 3 yes 4 (10/5) = 4(2) = 8 yes

*February 8, 2016*

**Math Questions**

7(16/8) = 7(2) = 14 yes 6 (10/10) = 6(1) = 6 yes

*February 8, 2016*

**Math**

9.25% monthly .095/12 = .0079167 so every month multiply by 1.0079167 y = 1,000 (1.0079167)^(12x) now just activate your calculator :)

*February 8, 2016*

**Maths**

f(x,y) = 2 (x^2 + xy + 3 y + y^2) How could that be less than 0?

*February 8, 2016*

**typos**

Increases ?? from 15 m/s to 6 m/s ??? anyway a = (final velocity - initial velocity) / time d = Vi t + (1/2) a t^2 = 15 (20) + (1/2) a (400)

*February 8, 2016*

**maths**

a + (n-1) d second is a + d = 15 fifth is a + 4 d = 24 so a = 15 - d and (15-d) + 4 d = 24 3 d = 9 d = 3 then a = 12 so term n is 12 + (n-1)3

*February 8, 2016*

**Math Please help me and fast**

yes if you had 5 x = 0 for example, that would work for any old x and you would have infinite number of solutions. This is the opposite case.

*February 8, 2016*

**Math Please help me and fast**

0 x = 2 x = 2/0 undefined 4 y = 12 y = 3 b - 9 > 20 add 9 to both sides b > 29

*February 8, 2016*

**Math**

1. yes y = 100 (1/2)^(t/3) 2. looks good, divide by 2 every three days 3. I can not very well show you a graph maybe google graph exponential or graph A * B^-(kt) 4. 100 /(1/2)^3 = 100/(1/8) = 800 so yes but do not understand how you did it

*February 8, 2016*

**Algebra**

P = K D^2

*February 8, 2016*

**Physics**

F = k *stretch for each each supports 7.35 * 9.81/3 = 24 N 24 = k (.21) k = 115 N/m agree except you use 9.8 for g I suspect K = 3 k from part a = 343 omega = 2 pi f = sqrt(K/m) = 6.83 radians/s f = omega/2pi = 1.09 Hz T = 1/f = .919 seconds agree V = A omega sin (omega t) max...

*February 8, 2016*

**social studies**

My guess: The promises England had made to Palestinians.

*February 8, 2016*

**Probability**

Well, I guess about half of them 99,000 + 00,000 ? = 100,000 so I suppose about 50,000

*February 8, 2016*

**Physics**

a = (final velocity-initial velocity) / time a = (0 - Vi)/1.7 so a = -Vi/1.7 d = Vi t + (1/2) a t^2 50.7=Vi(1.7) -(1/2)(Vi/1.7)(1.7)^2 50.7 = (1/2)(1.7)Vi Vi = 59.6 m/s then a = - Vi/1.7 = -35.1 m/s^2 so F = m a = 13(-35.1) = - 456 N

*February 8, 2016*

**physics**

F1 horizontal T at 40 degrees from Vertical T cos 40 = m g T = 10 * 9.81 / cos 40 = 128 N F1 = T sin 40 = 128 sin 40 = 82.3 N

*February 7, 2016*

**Physics**

F on glider from spring = -kx beginning x = .1 meter potential energy in spring = kd^2/2 where d is extension = 5 d^2/2 = 2.5 d^2 = 2.5 (.1-x)^2 the potential energy at start = 2.5(.1)^2 = .025 Joules total the kinetic energy = (1/2)mv^2 = .1 (.2)^2 = .004 Joules so .025 = ....

*February 7, 2016*

**physics**

F = 1050 - 916 = 134 N UP a = F/m = 134/93.5 = 1.43 m/s^2 UP in other words his speed down is slowing

*February 7, 2016*

**physics**

I guess you mean maximum height of 100 m Vertical problem: Vi = 59 sin A v = Vi - 9.81 t at top v = 0 0 = Vi - 9.81 t so t = 59 sin A /9.81 at top 100 = Vi t - (9.81/2) t^2 100 = (59 sinA)^2/ 9.81 -(9.81/2) (59 sin a)^2/9.81^2 100 = (1/2)(59 sin A)^2/9.81 980*2 = (59 sin A)^2 ...

*February 7, 2016*

**physics**

We just need to do the vertical part of the problem. I assume it hit the ground where H = 0 Vi = 15 sin 35 = 8.6 m/s up H = Hi + Vi t - 4.9 t^2 0 = Hi + 8.6 (2.7) - 4.9 (2.7)^2 Hi = 12.5 meters

*February 7, 2016*

**physics**

You are welcome. I am sorry; I have no schedule (retired and doing a lot of other stuff).

*February 7, 2016*

**physics**

and tan angle = 22.2/16

*February 7, 2016*

**physics**

typo sqrt (22.2^2 + 16^2)

*February 7, 2016*

**but the horizontal speed?**

25 = 4.9 t^2 t = 2.26 seconds, yes v = Vi - 9.81 t v = -9.81(2.26) = -22.2 BUT WHAT ABOUT u ? 16 m/s horizontal speed = sqrt (22.2^2+16)^2 tan angle below horizontal = 16/22.2

*February 7, 2016*

**math**

n * (n-1) = 90 the rest cancels agree n^2 - n = 90 n^2 - n - 90 = 0 agree n = 10 or n = -9 agree 10 * 9 [ (n-2)! / (n-2)! ] = 90 for me all right

*February 7, 2016*

**math**

2 W + 2 (2 W + 3) = 66 6 W + 6 = 66 6 W = 60 etc

*February 7, 2016*

**algebra**

term 2 = a r term 4 = a r^3 term 5 = a r^4 term 1 = 1 term 3 = a r^2 ---------------------- ar (ar^3) = 2 (a r^4) a^2 r^4 = 2 a r^4 2 a = a^2 a^2 - 2 a = 0 a = 0 (won't work) or a = 2 now we need r I assume you mean the sum of the first 4 is 80 a + ar + ar^2 + a r^3 = 80 1...

*February 7, 2016*

**Maths, Problem solving**

x + x/4 +(x-90) = 180 2.25 x = 270 x = 120

*February 7, 2016*