# Posts by Damon

Total # Posts: 30,138

**science**

usually mol in chemistry about 6.022140857 * 10^23 of anything Just like a "dozen" eggs is 12 of them. 6.022140857 * 10^23 is called "Avagadro's number". Google that for history. The significance is that 6.022140857 * 10^23 atoms of anything has the ...

**Geometry**

(x-h)^2 + (y-k)^2 = r^2 center at (h,k) radius r so for example number 3 center at h = 0 and k = 3 radius is 2 sqrt 3 so r^2 = 4*3 = 12 then (x-0)^2 + (y-3)^2 = 12 or for number 5 (x-a)^2 +(y-b)^2 = c^2

**Calculus**

Angle G = pi/3 + pi t/90 (we know pi/3 = 60 deg) dG/dt = pi/90 for side g g^2 = 225 + 400 - 600 cos G 2 g dg/dt = +600 sin G dG/dt at G = pi/3 g^2 = 325 g = 18 at G = pi/3 2*18 dg/dt = 600 sin pi/3 * (pi/90) dg/dt = 14.4 * pi/90 = .16 pi now the area s = (1/2) sum of sides s...

**Physics**

change in y = -7 change in x = -17 magnitude of displacement = sqrt(7^2+17^2) tan of angle below -x axis = 7/17 because in third quadrant where x and y are negative

**Lisa**

horizontal distance (not displacement vector) hd= sqrt (330^2 + 320^2) vertical distance = 10 total distance = sqrt(hd^2+100)

**Maths**

B traveled on a HEADING of 150 (around SSE) Draw position of B, 10 from origin at 60 degrees south of east (heading of 150) With center at B, draw a circle of radius 12 A is 8 km from the origin (can draw another circle if you want) at the intersection of the 12 radius circle...

**Physics 1st paper**

or just take components up the middle 2 * 8 cos (120/2) = 16 cos 60 = 8

**Math**

149.99999999........ to one significant figure = 100

**phisical science**

Force = rate of change of momentum momentum is p = m * v so force is rate of change of m * v if m is constant which is generally the case until you get to relativity then force = m *(rate of change of velocity) rate of change of the velocity of the mass is the acceleration of ...

**physics**

sqrt (30^2+20^2) =sqrt(1300) = 10 sqrt(13) tan A = 2/3 where A is compass angle CLOCKWISE from north

**Physics**

Liter = .1^3 m^3 = .001 m^3 so .8*1000 = 800 kg/m^3 which is 80% density of water

**physics**

yes force of gravity = m g distance = D work done by gravity = m g D Remember the tension in the cord also does work, but that was not asked.

**physics**

v^2

**History (1900’s)**

Google: No Irish need apply

**TYPOS ???**

15.3 sin(pi*5*6) + 44.1 no way I think maybe you mean 15.3 sin (pi x/6) but I do not believe that either because it should be colder in January than in July when you have sin (pi) which is also 0. This has maximum temp in April, no way

**math-precalculus**

t = (y-4)/2 from second equation so x = 4 [ (y-4)/2 ]^2 x = (y-4)^2 x = y^2 -8 y + 16

**Chemistry - Ionic Compounds**

Br ion is -1 in general Sr ion is +2 Ca ion is +2 Ga ion is +3 O ion is - 2 so Br and O are our negative ions match them up with the positives (metals) Sr and Br = SrBr2 Sr and O = SrO Ca and Br = CaBr2 Ca and O = CaO Ga and Br = GaBr3 Ga and O = Ga2O3 2*3=6 and 3*2=6

**maths**

The publisher evidently makes 9-4 = 5 dollars per book. It evidently costs 50,000 to print any number of books (strange, typo maybe) 5 x = 50,000 x = 10,000

**Statistics**

Hey, now I have done 2. What is the probability that you can do it now? Same old binomial distribution.

**Statistics**

find P of 5 successes (100 %) then subtract that from 1 p of success = .92 P of 5 in a row = .92^5 = .659 so probability that not all 5 work = 1 - .659 = .341

**Statistics**

binomial distribution we want chance of exactly 5 of 6 making it p(grow) = .7 so p(not) = .3 P(6,5) =C(6,5) .7^6 * .3^1 = 6 (.7)^6 * .3 = .212

**Physics**

When in danger or in doubt, keep the units and make sure they come out right. meters = meters/second * seconds :) L = v T f = 1/seconds so f = v/L = (meters/ second) / meters = 1/seconds

**typo**

191 Hz

**Physics**

so A yes .335 B yes 1536 C well lambda = 1.8 meters all right but 1.8 = v T = v/f f = v/1.8 = 343/1.8 = 1.91 Hz keep that distance = speed *time in mind

**Physics**

http://hyperphysics.phy-astr.gsu.edu/hbase/Waves/opecol.html

**Physics 11**

The speed is slower, but the same number have to pass you in a minute if you are sitting there watching. There is no storage closet for the waves. In other words the same answer as for your earlier question. L = v T T is constant v, the speed, decrease so L decreases (it gets ...

**Physics 11**

the frequency (and period) do not change) distance = speed * time or wavelength = speed * period 1 = 30 T so T = 1/30 L = 15 T = 15(1/30) = 1/2 so I agree

**Physics !! Help Needed UrGeNtLy!!**

Force applied * distance in direction of force = 25 * 2.5 It is not clear what besides friction the force is overcoming, perhaps acclerating, but it does not matter. Work done by the force is still the force times the distance.

**Math**

8 x + 12 (x+y) = 20 x + 12 y

**Physics**

weight of stationary object there = m g = G m M/r^2 so g = 6.67*10^-11*9.6*10^25 /(86,700,000+8,610,000)^2 b) v^2/r = g c) T = 2 pi r/v

**Math**

plus the one at zero (one more fence posts than fence sections :)

**Math**

(23*21*21)a^2

**Math**

5 h - 3[4k-6m+2h-6k] 5 h - 12 k + 18 m -6 h +18 k - h + 6 k + 18 m

**include data**

You not only want us to do the problem for you, you want me to Google the specific heat of copper and water. LOL 20 Cc (200 - T) = 60 Cc(T-30)+50Cw(T-30)

**Maths**

a b^2 - a c^2 ??????? a(b+c)(b-c) 10(5.5+4.5)(5.5-4.5) 10(10)(1) =

**Physics()**

F = k Q/r^2 5 at 0 and -3.5 at 60 for 0 k (5)/x^2 + k(-3.5)/(x-60)^2=0 5(x-60)^2 - 3.5 x^2 = 0 5(x^2-120x+3600 ) - 3.5 x^2 = 0 1.5 x^2 - 600 x +18,000 = 0 x = 32.7 or 367 32.7 makes no sense (introduced by squaring) so 367 cm

**physics**

I checked the units but not the constants

**physics**

sorry, missed the 2

** brakes for d meters**

initial speed = V final speed = 0 length of skid = L assume constant road/tire friction coefficient = mu a = magnitude of deacceleration 0 = V - a t so t = V/a time to stop L = V t - (1/2) a t^2 L = V(V/a) - (1/2)a(V^2/a^2) so L = (1/2)(V^2/a) a = V^2/2L now physics F = m a = ...

**Math**

3 / sqrt 15 * (sqrt 15/sqrt 15) = 3 sqrt 15 /15 = sqrt 15 / 5 Hey , just keep your cool and do them step by step.

**Math**

which one is (-3,-4) and (2,6) ?????

**Math**

guess? No need to guess !!!!

**Math**

2x+2 = x^2 + 3x -4 x^2 + x - 6 = 0 (x-2)(x+3) = 0 x = +2 ---> y = 6 or (2,6) x = -3 ---> y = -4 or (-3,-4) so I disagree with you

**physics**

Component of thrust up = 400,000 sin 37 Newtons Lift = 756,000 N perpendicular to course made good so lift up component = 756,000 cos 37 Newtons so m g =9.81 m = 400,000sin37+756,000cos37

**Chemistry**

Yes, I could not understand what Kylee was doing so did it myself.

**Chemistry**

checking my way Al = 27 g/mol 3.17 g = .1174 mols of Al I need 3 mol O2 for 4 mol Al mol O2/mol Al = 3/4 = x/.1174 x = .0881 mols O2 required O2 = 32 grams/mol .0081*32 = 2.82 grams of O2 needed BUT I only have 2.55 grams O2 SO Al is limiting

**maths**

diagonals of rhombus are perpendicular so we have right triangle one leg = 11 half of 22 diag one leg = x/2 half of other diag hypotenuse = 15 so x^2/4 + 121 = 225

**hyperbola I bet**

means hyperbola probably http://www.mathwarehouse.com/hyperbola/graph-equation-of-a-hyperbola.php

**steve reiny proportion help maths reiny!!!**

i = k cp /d^2 k*8/150^5 = k*5/d^2 8 d^2 = 5*150^2 d^2 = (5/8)150^2 d = 150 sqrt(5/8) d = 150(.79) d = 118.5cm lower it 150-118.5 = 31.5 cm

**hookle's law**

stretches 5 with 50 N so stretches 10 with 100 N 20 + 10 = 30

**math-probability**

permutations of 16 taken 3 at a time (order matters so permutations) 16!/[(16-3)!] 16!/[ 13! ] 16*15*14 3360 possible groups of 3 out of those 16 1/3360 = .000297 forget it unless you know a lot about the particular horses :) !

**math-probability**

This link will not help with your listing task but does show how to do the calculation with repeating elements. http://www.mathwarehouse.com/probability/permutations-repeated-items.php

**math-probability**

permutations does not normally include identical elements abcd is ok as is abdc but using a twice is not part of it there is no fast way to do what you asked that I know of

**Physics 11**

the first antinode is 1/4 wavelength from the fixed end. the second one is half a wavelength further so at L/4 and 3L/4 = .6 and 1.8 the fixed end is a node x = 0 the ANTInode is 1/4 L away, x = L/4 the next node is at L/2 , x = L/2 next ANTInode is at 3L/4 x=(3/4)L the next ...

**math**

I think you can do them all as standard linear programming problems. I gave you a link below. I do not know any method OTHER than by corners.

**linear programming**

http://www.wolframalpha.com/widget/widgetPopup.jsp?p=v&id=1e692c6f72587b2cbd3e7be018fd8960&title=Linear%20Programming%20Calculator&theme=blue

**math**

easy way 8 a - 4 b = 20 4 a - 8 b = 4 -------------- add these 12 a - 12 b = 24 divide both sides by 12 a - b = 2

**math**

center at origin by symmetry x^2/a^2 + y^2/b^2 = 1 given that b = 6 center to focus = 7 but 7^2 = a^2-b^2 49 = a^2 - 36 a^2 = 85 a = sqrt 85 so x^2/85 + y^2/36 = 1

**Why I knew wrong**

When I did it the easy way, I got a different answer, so went back and plodded through the hard way.

**REDO, did wrong**

call h a heart call x another suit d = 52*51*50 = 132600 combos we could get hhh =13*12*11/d = 1716/d hhx =13*12*39/d = 6084/d hxx =13*39*38/d = 19266/d hxh =13*39*12/d = 6084/d xxh =39*38*13/d = 19266/d xhx =39*13*38/d = 19266/d xhh =39*13*12/d = 6084/d add to get 77766/d= ...

**Math: Probability**

52/4 = 13 hearts in the deck 52-13 = 39 are not hearts probability that all 3 are H = 13/52 *12/51*11/50 = .01294 probability that 2/3 are H =13/52 * 12/51* 39/50 = .04588 {39 is number of non hearts} probability that 1/3 is H = 13/52 *39/51*38/50 = .14529 add A) 0.2041

**Maths**

http://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html Xn = a + d (n-1) 19 = a + d(8) 37 = a + d(15) ------------subtract to eliminate a solve for d solve for a X17 = a + d (16)

**physics**

a = (29.0 - 33.0)/2.50 = - 1.60 m/s^2 d = Vi t + (1/2)a t^2 d = 33.0(2.50) - 0.800(2.50)^2

**Math**

You are welcome. I think they left out the 38 percent who majored in physics :) (To get 70% you counted the 8 twice, I think really the total is 62 but they gave percent, not number of students so it is out of 100 )

**Math**

43/100 women 15/100 art take away the 8/100 that are both yes I get 1/2

**Math help asap**

You mean (5 , 4) I hope. Draw it. eg (5,0), (0,0) , (0,4) and our (5,4) or (5,0), (10,0) , (10,4) and our (5,4)

**math**

well you could solve the equations for a, b and c but your way is more fun You have too many a s though. There should be 2 of each letter a+b + b+c + a+c = 8 2a + 2b + 2c = 8 so a+b+c = 4

**Algebra**

J speed is one thing/30 min B speed is one thing/45 min total speed is 1thing/30min + 1thing/45 min = (1/30+1/40) things/min = 7/120 things/min or 120/7 minutes/thing :) 120/7 = about 17.1 minutes

**Physics 11**

To make it easy for yourself think of a harp string half a wavelength long. In its lowest frequency it has nodes at the two ends which are fixed, half wavelength apart. Then the antinode is in the middle which is 1/4 wavelength from each end :)

**Physics 11**

L/4 , 3L/4 .......... every 1/2 wavelength thereafter so .6 , 1.8 ... etc http://en.wikipedia.org/wiki/Standing_wave

**Physics**

well, assuming that the string exerts no torque on the wheel and that the string is of zero mass, there is nothing to change the tension in the string as it runs over the wheel. (In real life of course the wheel has mass and moment of inertia and the difference in tension on ...

**Math**

3 ( sec x * d tanx/dx + tan x * d sec x/dx )

**Math**

2 * 5404 4 * 2704 4 * 4 * 676 4 * 4 * 4 * 169 4 * 4 * 4 * 13 * 13 sqrt of that is 2 * 2 * 2 * 13 which is 104

**Math**

2 m = 15 + 1 m so m = 15 minutes ( and 30 cents )

**Physical science CHECK my answers**

6. Agree 7. Disagree 8. Disagree

**TYPO**

thus 143 at ABT see a few lines down

**one way of many to do it**

Call T the top call G the bottom T G B is a right triangle 37 at B, 90 at G, thus 53 at BTG TGA is a right triangle 25 at A, 90 at G, thus 65 at ATG thus 122 at ABT law of sines: sin 25 / BT = sin 12/ 57 so BT = 156 meters (first answer) now angle ABT = 180 - 12 - 25 = 143 so ...

**Ah, here :**

http://betterexplained.com/articles/easy-permutations-and-combinations/

**algebra 1**

You better either read the chapter or Google permutations !

**physics**

a liter is 10 cm * 10 cm * 10 cm or 1000 cm^3 so a mL is 1 cm^3 so 20 mL is 20 cm^2 we added a volume of: 6 cm * 6 cm * 6 cm is 216 cm^3 so if the cube is submerged, the scale on the side of the cylinder should now read 236 cm^3 by the way you sure that cube is not 6 mm on a ...

**Physics**

cc = cubic centimeter density = 6.5 grams/cc volume of cube = 20*20*20 = 8,000 cc so mass = 6.5 gms/cc *8, 000 cc = 52,000 gms = 52 Kg 13 kg (8,000cc/52kg) = 2,000 cc

**Math**

m = r + 7 m + r + 1 = 3 r so m = 2 r - 1 so r+7 = 2 r - 1 8 = 1 r Rosa is 8 m = 8 + 7 = 15

**History**

LOL - I think that is usually called the "partition" of Poland. That was indeed Catherine the Great of Russia plus the two Germanic countries of Prussia and Austria.

**History**

The history of Poland is far too complicated for that question. Many "colonization" efforts in Poland were made by Germans though. Moreover I do not know which Russian-Polish war you mean. Catherine the Great?

**Algebra**

change in f(x)/change in x = (9-64)/(4-1) = -55/3

**Pre-Calculus 12**

(x-5)(x+2)/(x-2) well we know it is 0 at x = 5 and at x = -2 and we know it explodes at x = 2 we know it goes to y = x as x gets +big we know it goes to y = -x as x gets -big now between those zeros at -2 and+5 lies x = 0 when y is 10/2 = 5 so that is a start :)

**Math**

35 km *( 6" /35km) = 6"

**Heading?**

300 mph on what heading? Usually you give the direction a wind is coming from, like a North wind caries you south. Here do you mean it blows you North? In any case use vector components North component = 50 + 300 cos A East component = 300 sin A where A is the heading angle ...

**College Algebra**

(5/64)x = 15/8 = 120/64 x = 120/5

**College Algebra**

you cut four planks out of it 4*3.25 = 13 feet used that leaves 2 1/2 feet

**Notation ?**

to write 5 to the third power you type 5^3 so maybe I am guessing the first one might be f(x) = .4* 3^x ??? that would be like .4*3 .4*9 .4*27 etc, growing exponentially ---------------------- however 3 * .5^x would be like 3 * .5 3 * .25 3 * .125 sinking like a rock same for...

**Physics**

ok x is east y is north Ax = 6 cos 30 Ay = -6 sin 30 Bx = 0 By = 13.9 Cx = -5 cos 45 Cy = -5 sin 45 so Dx = +6 cos 30 - 5 cos 45 Dy = -6 sin 30 + 13.9 -5 sin 45 |D| = sqrt (Dx^2 + Dy^2)

**missing decimal points or something**

300 south of east? that is 60 degrees short of all the way around to east again maybe 30.0 ? same with 450 south of west

**Mathmatics**

120/360 = 1/3 so we want one third the area of the circle (1/3) pi (81) =

**Math**

7 (10 + 2 ) ?

**Algebra**

s = height above ground s = 60 + 20 t - 4.9 t^2 (standard physics equation on earth) at t = 0 s = 60 (clearly :) now when does it hit the bleak earth? That is when s = 0 4.9 t^2 - 20 t -60 = 0 solve quadratic and use the positive t (the negative t was back before you threw it ...

**Algebra (answer check)**

hmmm .94^6 * 12500 = 8623 slope = m = (5-2)/(-3+4) = 3 y = 3 x + b 5 = 3(-3) + b 5 = -9 + b b = 14 so y = 3 x + 14 so none of your answers. You probably have a typo. even is 2, 4, 6 so 4 of the six sides are even or 5 4/6 = 2/3

**physics**

to prevent sliding down: F sin T >/= m g - mu m g cos T to prevent sliding up F sin T </= m g + mu m g cos T

**physics**

If theta is the angle above horizontal and there is no friction then F sin theta must be = m g if theta = 0 , F is infinite if theta = 90 degree, F = m g

**math**

Area of what I assume is supposed to be a rectangle is (1/2)(1/4) = 1/8 of a square mile