# Posts by Damon

Total # Posts: 29,750

**Chem**

3 * .25 * 6 * 10^23

**Chem**

You need 3 mol of A for every mol of B but you only have 2 mol A so you only use 2/3 of a mol of B that would yield 4/3 mol of C but we only got 1 mol of C 100 * 1/(4/3) = 75 % yield

**Math**

Take the average speed during each second times one second and add 6+9+8+7.5+10.5+8.5+6.5+9+8+9 = 82

**Chemistry**

grams/mol N=14 H=1 F= 19 so NH3 =17 F2 = 38 HF = 20 so If I have 4 g of NH3, how many g of F2 do I need? 4/[2(17)] = x/[5(38)] x = 20*38/34 = 22.4 g F2 whoops, not enough F2 so use 14 of F2 and y of NH3 y/34 = 14/190 y = 2.5 grams of NH3 then 2.5/34 = HF/[6(20)] HF = 8.82 ...

**pre algebra**

168 miles/3.5 hours = 48 mi/h

**Chemistry**

See below, I got 500

**Chemistry**

P V = n R T n is number of mols say we have 1 mol (n=1) of argon, 40 grams then we have 40 grams of Methane which is 40/16 or 2.5 mols (n=2.5) they both have the same V and T P/n = RT/V = same for each 200/1 = Pmeth/2.5 Pmeth = 2.5*200 = 500 torr

**Chem 112**

Zn = 65.4 grams/mol Cl = 35.5 grams/mol H = 1 gram/mol so 2HCl = 2(36.5g/mol) = 73 g ZnCl2 = 136.4 g/mol to get 1 gram ZnCl2 need (1/.684)(65.4/136.4)= .701 grams Zn

**Math**

original height = H h(t) = height dh/dt = -2cm/20min = -0.1 cm/min so h = H - 0.1 t h in cm, t in minutes

**phyisics**

You mean it stopped after 8 meters? If so average speed = (3+0)/2 = 1.5 m/s so t = 8/1.5 = 80/15 = 5.33 seconds sliding to a stop then acceleration a = (0-3)/5.33 = -.5625 m/s^2 so now the physics F = m a -m g (mu) = m (-.5625) mu = .5625/9.81 = .0573

**Calculus**

df/dx = -3 df = -3 dx |.05| = -3 |dx| |dx| = .01667 check if x = 1.01667 f(x) = -3(1.01667) + 2 = -3.05+ 2 = -1.05 distance from -1 is .05 sure enough

**chemistry**

answered this below

**chemistry**

2Mg + O2 ---> 2 MgO Mg = 24.3 g/mol O = 16 g/mol so 48.6 grams Mg + 32 grams O2 --> 80.6 grams MgO 5/80.6 = .062 mol MgO produced x/32 = .062 x = 1.985 grams O2 and we needed y/48.6 = .062 y = 3.00 grams of Mg sure enough

**chemistry**

if the masses are equal, the diamond has more volume because it is less dense.

**Math**

well, let's try the 20 on the bottom and the 15 sloping up toward the right. Try the diagonal connecting the two right ends. draw altitude h that divides the base into x and (20-x) x^2+ h^2 = 225 so h^2 = 225-x^2 (20-x)^2 + h^2 = 625 ----------------------- 400 -40 x + x^2...

**science**

original momentum = .04*500 = 20 kg m/s that will be the final momentum so 6 v + .04*200 = .04*500 6 v = .04*300 v = .04*50 v = 2 m/s

**Science**

Probably very hungry. They might not recognize the orchids as food. Many might die. I do not know anything about the relative nutritional value of cactus and orchid flowers. That would determine if a low surviving population would continue feeding on the few cactus plants or ...

**Finite math**

5 c + 7 s + 9 a = 6100 c + s + a = 900 a = .5 (c+s) or 2a - c - s = 0 ============================ add two and three 3 a = 900 so a = 300 c+s = 600 so s = 600 - c 3 c + 7 s + 2700 = 6100 3 c + 7(600-c) = 3400 3 c + 4200 - 7 c = 3400 4 c = 800 c = 200

**Physics 20**

No, the asteroid does NOT have a mass of 2.71 kg. That would be about the mass of a gallon or so of milk. I said 2.71*10^20 kg

**Physics 20**

READ A is 7620 m/s B is 2.71*10^20 kg

**Physics 20**

A is 7620 m/s B is 2.71*10^20 kg and for heaven's sake use SCI units, do not use km and hours or something. Use meters, seconds, Newtons, kilograms. 1 hour = 3600 seconds 1 km = 1000 meters

**Physics 20**

B) v(9.06*10^3) = 2 pi (311) v = .216 m/s I do not think so, suspect you mean 311km not 311 m that would give v = 216 m/s then 7620^2 = G Ma/r 7620^2 = 6.67*10^-11 Ma/311 Ma = 2.71*10^20 kg

**Physics 20**

v^2 = G Me/r v^2 = (6.67*10^-11)(5.97*10^24) /6.85*10^6 v^2 = 5.81 * 10^7 = 58.1*10^6 so v = 7.62*10^3 so v = 7620 meters/second

**Physics 20**

A)when in orbit about earth mv^2/r = m (G Mearth)/r^2 solve for v B) same equation but get v immediately v T = 2 pi r then m v^2/r = m Ma(G/r^2) m , mass of sat cancels we know v solve for Ma

**Physics 20**

I did B

**Physics 20**

Weight is NOT in kg but in Newtons !!!!!! F = m * 9.81 = 154*9.81 = 1510 Newtons

**Physics 20**

A) F = G m Me /r^2 at surface G Me/r^2 = 9.81 B) answer to A*r^2/(r+222,000)^2 but if you try to measure it with a scale, zero because F is balanced exactly by mv^2/R if in orbit which is the answer to part C. Really weight in orbit means nothing.

**Physic**

x = 1.6 (pi)cos(pi*1.3 +pi/3) = 5.03 cos (1.63 pi) = 5.03 * .397

**Algebra**

(A/2) -5 = 35 A/2 = 40 A = 80

**Health**

yes. Despite the act that it ends in s, it is one disease.

**Physics 20 Energy**

m g (change in height) 85 * 9.81 * 2.4 *1000 Joules

**Physics 20**

5(2.5)^2 =5*6.25

**huh??**

It is a four dimensional pool?

**Chemistry**

H2O = 18 g/mol so I have 5.5/18 mols water you get two mols H2O for every mol of O2 so I used 5.5/36 mols O2 O2 = 32 g/mol so 5.5*32/36 = 4.89 grams O2

**Chemistry**

Fe2O3 + Al ---> Al2O3 + Fe same number of mols of Fe as of Al Al = 30 g/mol so 225/30 mols of Al so 225/30 mols of Fe so (225/30) mol mass of Fe (225/30)56 = 420 grams of iron

**Nope**

Look at it on a number line. for positive x-3 x must be to the right of 3 but then sqrt x must be greater than sqrt (x-3) which is not possible. If it were -3 on the right, that would be different (x-3)^.5 - x^.5 = 3 square both sides [(x-3)^.5-x^.5][(x-3)^.5-x^.5] = 9 (x-3)-2...

**Physics 20 Gravity**

11.2 m/s^2 as compared to 9.81 on earth

**Physics 20 Gravity**

g = F/m = G M/r^2 where G = 6.67*10^-11 M = 7.66*10^24 r = 6.74*10^6

**English**

maybe something like: Increased government subsidies would make US manufacturers more competitive with heavily subsidized foreign industries.

**Algebra**

height/shadow = 3.4/1.73 = h/48.25 so h = (3.4/1.73)48.25 which is 3.4 * 48.25/1.73 or 94.8 Draw a picture !!!!

**maths help plz sir damon steve or reiny**

This might help: http://tutorial.math.lamar.edu/Classes/DE/HOVariationOfParam.aspx

**whoops**

825/10,000 or 33/400

**Algebra**

8.25/100 = 825/1000 divide top and bottom by 25 to get = 33/40

**Algebra**

.06*$70 = $4.20 it is supposed to be in dollars accurate to the penny

**Algebra**

120-84 = 36 (36/120)100 = 30%

**Math**

[ (7/3) +2 ] /[-3 -(3/2)] (13/3) / (-9/2) = -26/27 I get B

**chemistry**

I suppose w is weight? I suspect you mean mass in grams water is about 1 gram/cm^3 or 1 kilogram/liter so our NaCl here is .075*1 = .075 kg per liter or 75 grams/liter so the real question is How many mols is 75 grams of NaCl NaCl = 58.5 grams/mol (23+35.5) so 75 g (1mol/58.5g...

**algebra**

7/3 = 2 1/3 or 2.33333.......

**algebra**

0.164*188 = 30.8

**Physics**

h = 20 + .4 t - 4.9 t^2 solve for t when h = 0 just like the problem you posted below this one. also the speed when it hits the ground is the same method.

**Physics**

h = 1.5 + 2.5 t -4.9 t^2 when is h = 0? solve quadratic for t 4.9 t^2 -2.5 t - 1.5 = 0 you could use http://www.math.com/students/calculators/source/quadratic.htm Note, quadratics have two solutions of course. In this problem if you get a neagative time, that is how long ago ...

**Physics**

d = 13.9 * .6 + (13.9/2)t because average speed during deacceleration = half the original speed time to stop during acceleration is t: v = Vi + a t in general so 0 = 13.9 - 3 t t = 13.9/3 so in the end d=13.9*.6 + (13.9/2)(13.9/3) part b will you go 35+9.5 meters in time? what...

**Physics**

a)assume you mean Vx=1.4t^2+1.1t v = 1.4(16) + 1.1(4) b) change in velocity = answer to part a since velocity at t = 0 was 0 so divide a the answer to part a by 4 seconds

**Oh, use Reiny reply**

I did not see the reversal of direction

**Physics (typo?)**

30 min = .5 h 10 min = 1/6 h 20 min = 1/3 h ================= d = 140*.5 + 90/6 + 90/3 (it went 90 for a total of 1/2hour???? typo I bet) average speed = d /total time the way you wrote it the total time is one hour, but I doubt it.

**science doppler to and fro**

what frequency does the blood hear? for observer toward source: f' = f (v+Vobserver)/v f' =6.113*10^6(1570+.3979)/1570 calculate f' the blood particle serves as a transponder sending back a signal at that f' now the source is moving toward the observer f"...

**Physics**

for speed divide the distance by the time for velocity divide the DISPLACEMENT by the time displacement is a vector with x y and perhaps z components. All the way around a track is a Distance of 2 pi r BUT a displacement of ZERO

**science chemistry**

Particles maintain their distance and orientation to other particles in the solid state and only vibrate a little in place so the shape and volume of a lead block does not change (much:). In the liquid state, the particles maintain their distance but not orientation so the ...

**Physics 11 question pls urgent HELP!!!!!**

No The CHANGE in speed is acceleration times time 12.5 * 3.25 That is all you need The initial speed is not relevant. momentum change = mass*change in velocity = 1205*12.5*3.25 kg m/s

**math**

the whole thing is 14 m by 8 m so the walkway area is 14*8 - 12*6

**physics**

here.... +small ...... -big x ......... 0.......... 4.35 just using distances without regard to sign to get equal field magnitudes 1.90/x^2 = 3.61/(x+4.35)^2 solve for x, note it has to be - (left of origin) 3.61 x^2 = 1.9(x^2 +8.7 x+18.9) 3.61x^2 = 1.9x^2 + 16.5x + 35.9 1.71x...

**Science**

The birds reproduce in six months? The birds did not use the O2 in the water directly. Even cormorants breathe air above the water :) However the fish did. I think there might possibly be more fish in 6 months but doubt if the birds would react that quickly.

**oic**

oh, did not notice the "undefined" line is x = 2 vertical line

**Algebra**

slope = (9-2)/(x-2) =7/(x-2)

**Algebra**

LOL - three ways to get at that same parabola

**Algebra**

that is a parabola, where is the vertex? 16 t^2 - 96 t = -h +256 t^2 - 6 t = (1/16)(-h + 256) t^2 - 6 t + (6/2)^2 = (1/16)(-h + 256) + 9 (t-3)^2 = (1/16)(-h + 256) +(1/16)(144) (t-3)^2 = -(1/16)(h-400) vertex at 3 seconds and h =400 ft

**math please help**

so 12.5/100 = 125/1000 = (5*25)/(40*25) =5/40 =1/8

**Further mathematics**

say 15 N along x axis and 10 N 60 deg above -x axis x force = 15 - 10 cos 60 = 10 y force = 10 sin 60 = 8.66 magnitude = sqrt(100+8.66^2) tan angle above +x axis = .866

**Maths lit**

32*0.794 Kg

**Math**

r = 0.045 Ai = 500 dA/dt = Ar dA/A = r dt ln A = r t A = Ai e^rt 2500 = 500 e^.045 t 5 = e^.045 t ln 5 = .045 t so t = ln 5/.045 =1.61/.045 = 35.8 years

**US History**

I am no expert but in this period of westward expansion of cattle range after the Civil War I think both c and d are appropriate answers.

**MATH**

11 - G

**math**

(5/20)100 = 25%

**sorry, yes**

8C4 = 8!/[4!(4!)] = 8*7*6*5/(4*3*2) = 70 so 15*70 = 1050

**MATH HELP**

2 out of 6 administrators 4 out of 6 others combinations of 6 taken 2 at a time = 6!/[ 2!(4!)] =6*5/2 = 15 combinations of administrators combinations of 6 taken 4 at a time = 6!/[ 4!(2!)] = 6*5/2 = 15 combinations of faculty and students so 15*15 = 225

**Partial Sums and finding a certain term**

S3-S2 = term 3 S3 = 13/17 S2 = 8/12 maybe 13/17 - 8/12 ??? about .098

**Algebra**

-11 x^5 +4x +8x^3 -13x -2 +7x^3 -11x^5 +15 x^3 -9x -2

**Triangles math**

fraction = percent /100 2*0.5 and 3*0.5 2*3 and 3*3 2*5 and 3*5

**math**

2/5 of 5/12 = 1/6

**math**

2/3 left after pie 3/8 of that left 2/3 * 3/8 = 1/4 really the same as your problem above

**social studies**

and you are right.

**physics**

energy = q V = 16 q so (1/2) m v^2 = 16 q

**physics**

g sin theta = constant = your gravitational acceleration for this problem, all it ourg m a = -kx + m ourg = m d^2x/dt^2 x = Xi + xh sin 2 pi t/T Xi is our equilibrium x when a = 0 Xi = m ourg/k now if harmonic then xh is our harmonic motion x do it separate as added to Xi x = ...

**Trigonometry**

sqrt(49+9) = sqrt(58) =7.61 tan angle above -x axis = 3/7 A = .405 radians *180/pi = 23.2 deg so angle counterclockwise from x axis = 180-23.2

**LOL - hardly**

If I knew this was for a test I would not be doing it.

**Math (help if you know the full test)**

5/16 = .3125 which is 31.25 %

**science(physics)**

Try a turn, look at Ac = v^2/R needs side force from road at bottom moment about CG is balanced by light force up on inner tires and heavy force up on outer tires. The higher the CG, the longer that moment arm. When v^2/r is high enough, inner tires lift off road.

**math**

Na = .05*10 + .02*5 = .6 percent NaCl = .6/15 *100 = 4% =.04 .04/15ml = 40/15 grams/liter so what is 40 grams of NaCl in mols? 40g/58.44 g/mol = .684 M

**physics**

impulse = force * time = change of momentum the key word is "quick"

**maths**

w = 2h+3 total w = w+5 total h = h+5 A = (w+5)(h+5) = w h + 5w + 5h + 25 = (2h+3)h + 5(2h+3) + 5h +25 = 2h^2 +3h +10h +15 +5h + 25 = 2h^2 + 18h + 40 = 2(h^2 + 9 h + 20) =2(h+4)(h+5)

**Maths**

(3km/60min)20min = 1 km

**Algebra 2**

combinations of 18 taken 10 at a time = 18!/[ 10!(18-10)!] = 18*17*16*15*14*13*12*11/ (8*7*6*5*4*3*2) = 17*16*15*14*13*12*11/(8*7*5*4*2) = 17*15*14*13*12*11/(7*5*4) = 17*3*2*13*3*11 = 43,758

**Algebra 2**

combinations of 6 taken four at a time same method as your other problem 6*5/2 = 15

**Algebra 2**

well, around four times :) d = k v^2 49 = k (900) k = 49/900 d = (49/900)(65)^2 = 230 feet

**Maths**

h/5 = 20/(25+5) h = 100/30 = 10/3 = 3.33 ft

**Physics**

average speed = (8+0)/2 = 4 m/s so t = .30 meters/4 meters/s =.3/4 s Force * time = change of momentum or impulse F(.3/4) = .5 * 8 F = (5/3)(32) = 53.3 Newtons

**history**

One factor: Rotten governments in the Byzantine Empire, Persia, Mesopotamia, the Levant, Egypt, North Africa, Spain and much of Asia. Serious resistance resulted when they ran into the Franks in France.

**math**

about 780 http://davidmlane.com/hyperstat/z_table.html

**Algebra 6**

2 y + 1 x + 2 = 1 x + 2 y + 2 0 = 0 true for any x and y

**Algebra 2**

1<11 and 1>-3 :) yes a