Monday

January 23, 2017
Total # Posts: 28,866

**Calculus**

f(3) = 0 f(0) = 9 slope = (0-9)/3 = -3 f' = -2x where is -2x = -3 ? x = 1.5

*January 22, 2017*

**Chemistry**

volume = 2.3 ml mass = 1.0107*10^-2 kg =10.107 grams density= m/v =10.107/2.3 = 4.39 g/mL maybe Titanium ?

*January 22, 2017*

**Chem**

3 * .25 * 6 * 10^23

*January 22, 2017*

**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

*January 22, 2017*

**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

*January 22, 2017*

**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 ...

*January 22, 2017*

**pre algebra**

168 miles/3.5 hours = 48 mi/h

*January 22, 2017*

**Chemistry**

See below, I got 500

*January 22, 2017*

**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

*January 22, 2017*

**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

*January 22, 2017*

**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

*January 22, 2017*

**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

*January 22, 2017*

**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

*January 22, 2017*

**chemistry**

answered this below

*January 22, 2017*

**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

*January 22, 2017*

**chemistry**

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

*January 22, 2017*

**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...

*January 22, 2017*

**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

*January 22, 2017*

**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 ...

*January 22, 2017*

**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

*January 22, 2017*

**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

*January 21, 2017*

**Physics 20**

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

*January 21, 2017*

**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

*January 21, 2017*

**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

*January 21, 2017*

**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

*January 21, 2017*

**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

*January 21, 2017*

**Physics 20**

I did B

*January 21, 2017*

**Physics 20**

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

*January 21, 2017*

**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.

*January 21, 2017*

**Physic**

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

*January 21, 2017*

**Algebra**

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

*January 21, 2017*

**Health**

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

*January 21, 2017*

**Physics 20 Energy**

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

*January 21, 2017*

**Physics 20**

5(2.5)^2 =5*6.25

*January 21, 2017*

**huh??**

It is a four dimensional pool?

*January 21, 2017*

**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

*January 21, 2017*

**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

*January 21, 2017*

**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...

*January 21, 2017*

**Physics 20 Gravity**

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

*January 21, 2017*

**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

*January 21, 2017*

**English**

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

*January 21, 2017*

**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 !!!!

*January 21, 2017*

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

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

*January 21, 2017*

**whoops**

825/10,000 or 33/400

*January 21, 2017*

**Algebra**

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

*January 21, 2017*

**Algebra**

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

*January 21, 2017*

**Algebra**

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

*January 21, 2017*

**Math**

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

*January 21, 2017*

**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...

*January 21, 2017*

**algebra**

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

*January 21, 2017*

**algebra**

0.164*188 = 30.8

*January 21, 2017*

**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.

*January 21, 2017*

**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 ...

*January 21, 2017*

**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...

*January 21, 2017*

**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

*January 21, 2017*

**Oh, use Reiny reply**

I did not see the reversal of direction

*January 21, 2017*

**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.

*January 21, 2017*

**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"...

*January 21, 2017*

**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

*January 21, 2017*

**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 ...

*January 21, 2017*

**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

*January 21, 2017*

**math**

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

*January 20, 2017*

**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...

*January 20, 2017*

**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.

*January 19, 2017*

**oic**

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

*January 19, 2017*

**Algebra**

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

*January 19, 2017*

**Algebra**

LOL - three ways to get at that same parabola

*January 19, 2017*

**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

*January 19, 2017*

**math please help**

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

*January 19, 2017*

**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

*January 19, 2017*

**Maths lit**

32*0.794 Kg

*January 19, 2017*

**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

*January 19, 2017*

**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.

*January 19, 2017*

**MATH**

11 - G

*January 18, 2017*

**math**

(5/20)100 = 25%

*January 18, 2017*

**sorry, yes**

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

*January 18, 2017*

**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

*January 18, 2017*

**Partial Sums and finding a certain term**

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

*January 18, 2017*

**Algebra**

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

*January 18, 2017*

**Triangles math**

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

*January 18, 2017*

**math**

2/5 of 5/12 = 1/6

*January 17, 2017*

**math**

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

*January 17, 2017*

**social studies**

and you are right.

*January 17, 2017*

**physics**

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

*January 17, 2017*

**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 = ...

*January 17, 2017*

**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

*January 17, 2017*

**LOL - hardly**

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

*January 17, 2017*

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

5/16 = .3125 which is 31.25 %

*January 17, 2017*

**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.

*January 17, 2017*

**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

*January 17, 2017*

**physics**

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

*January 17, 2017*

**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)

*January 17, 2017*

**Maths**

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

*January 17, 2017*

**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

*January 17, 2017*

**Algebra 2**

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

*January 17, 2017*

**Algebra 2**

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

*January 17, 2017*

**Maths**

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

*January 17, 2017*

**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

*January 17, 2017*

**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.

*January 16, 2017*

**math**

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

*January 16, 2017*