Wednesday

September 28, 2016
Total # Posts: 27,171

**Chemistry**

choices A. H>0, S>0 , G<0 B. H<0, S>0 , G<0 C. H>0, S>0 , G>0 D. H<0, S<0 , G>0

*July 16, 2016*

**Chemistry**

Marcela dissolves 80.0 g of ammonium nitrate in 50.0 mL of water at room temperature and notes that the temperature of the solution decreases by 5.0°C. Which correctly designates the signs of changes of G, S and H for this reaction?

*July 16, 2016*

**Missing data for binomial distribution problem**

We need to know how many she planted. Given n, use binomial distribution with p = 0.95 and 1-p = 0.05

*July 16, 2016*

**math**

http://www.jiskha.com/display.cgi?id=1468692682

*July 16, 2016*

**math**

red each is 3/20 green each is 4/40 which is 1/10 so 10(3/20) + 50(1/10) = 1.50 + 5.00 = 6.50 ah well, not on the list. Typo?

*July 16, 2016*

**math**

let me see 5 7 11 13 I think mean = (5+7+11+13)/2 = 36/4 = 9 median = (7+11)/2 = 9 When there are an even number of items it is impossible to pick the same number above and below any particular one. Therefore you take the average of the two middle ones.

*July 16, 2016*

**physics**

original is r v = 5 r then later same v = 4 (r+2) so 5 r = 4 r + 8 r = 8 ohms

*July 16, 2016*

**no, physics :)**

9 because 3^2 = 9 or because 3 s has 1 3 p has 3 3 d has 5 and 1 + 3 + 5 = 9 Note, each of those orbits can have electrons with spins of + or - 1/2 so total of 18 electrons for n = 3

*July 16, 2016*

**statistic**

3 b 2 b, 1 g 1 b, 2 g 3 g so 4 possible outcomes, all equally likely p of each is .25

*July 15, 2016*

**Geometry**

6.75 in (1 ft/.25 in) = 27 ft 4.50 in (1 ft/.25 in) = ?????

*July 15, 2016*

**calc**

Angle to what? Not knowing do not know sin or cos F (cos 48 or sin 48)(0.45) = 175

*July 15, 2016*

**Physics**

Ah yes, just noticed you said 5, good

*July 15, 2016*

**Physics**

C =q/V so x = q/68 that q is all the charge we have now for both capacitors total C = 12*10^-6 + x q = 20 (12*10^-6 + x) 68 x = = 240*10^-6 + 20 x 48 x = 240 * 10^-6 x = 5 *10^-6 Farads or 5 µF

*July 15, 2016*

**You are right, impossible**

Force is change of momentum / time = change in m v / t You have to know the time

*July 15, 2016*

**Physics**

horizontal speed u = 30 forever so what is vertical speed v? v = g t v = 9.81(3) that is also around 30 m/s so speed = sqrt(u2+v^2) = sqrt 1800) = about 42 do it all better with calculator

*July 15, 2016*

**physics**

Tricky pulse speed increases as you toward center at every r, acceleration, a, which is like a variable g for us a = omega^2 r This is like the plse on a hanging rope problem see: http://www.usna.edu/Users/physics/mungan/_files/documents/Scholarship/HangingPulse.pdf

*July 15, 2016*

**physics**

Suspect speed is 33.3 m/s average speed during stop = 33.3/2 =16.65 time to stop = t = 30/16.65 = 1.80 s d = .5 a t^2 30 = .5 a 1.8^2 so a = 18.5 m/s^2 so F = m a = 1000*18.5 = 18,500 Newtons

*July 15, 2016*

**Math**

so 11 girls, so what is the question?

*July 15, 2016*

**hey, I do not need this much practice, already passed subject**

now wait a minute, this is too much like the last one. You try for a while. I already know how.

*July 14, 2016*

**physics**

Well, now we seem to be back in the dark ages of some king's feet. v1 = 42*5280/3600 ft/s v2 = 58*5280/3600 ft/s assuming constant acceleration we can use average v va = 50*5280/3600 ft/s so t = 660/va a = (v2-v1)/t

*July 14, 2016*

**physics**

26.8 m/s = 60 mph You do not say but I assume you mean 60 mph or 26.8 m/s v = a t 26.8 = a (3.2) a = 26.8/3.2 d = (1/2) a t^2 = .5 (a) (3.2)^2

*July 14, 2016*

**Math**

I guess you mean log base b of a = c log a = c b^(log a) = a = b^c if a<1 and b >1 then fraction = big number^c hmm it would be helpful if c <0 like fraction = b^c = 5^-2 = 1/25 if a<0 and b >1 then logb (-something) oh my, we are trying to take the log of a ...

*July 14, 2016*

**Math**

You are welcome.

*July 14, 2016*

**Math**

d = 2 n q = .5 n 5 n + 10 d + 25 q = 30,000 cents 5 n + 20 n + 12.5 n = 30,000 37.5 n = 30,000 n = 800 so q = 400 D

*July 14, 2016*

**MATH**

You want the inverse of: y = (1/3)^x ????? hmmm maybe try x = (1/3)^y ln x = y ln(1/3) y = ln x /ln(1/3) = -ln x ln 3 y = - 1.1 ln x approximately

*July 14, 2016*

**Chemistry**

You are welcome namesake :)

*July 14, 2016*

**Chemistry**

thanks dude !

*July 14, 2016*

**Chemistry**

mols N2H4/ mols H2O2 = 1/2 mols N2H4/mols water = 1/4

*July 14, 2016*

**Chemistry**

N2H4 + 2H2O2= N2 + 4H2O What are the mole ratios of hydrazine (N2H4) to hydrogen peroxide (H2O2) and hydrazine to water

*July 14, 2016*

**pre cal**

u dot v = revenue which is sum of number of each times price of each so 1.05 ( u dot v )

*July 14, 2016*

**physics**

1 km * 1000 m/km * 1 s/4 m * 1 min/60 s = 250/60 = 25/6 minutes

*July 9, 2016*

**physics**

factors: 1609 m/mi 3600 s/h 1000 m/km 24 hr/d ======================= (.9mi/.5h) = 1.8 mi/h =========================== now (1.8mi/h)(1609m/mi)(1h/3600s) = (1.8*1609/3600) m/s ==================== (1.8*1609/3600)m/s (1km/1000m)(3600*24 s/d) = 1.8*1.609*24 km/d

*July 9, 2016*

**physics**

70 mi/h *1 h/60 min = (7/6)mi/min (7/6)(mi/min)(24 min) = 7*4 mi = 28 miles

*July 9, 2016*

**Math (money)**

c > 17+ 8 or c > 25

*July 9, 2016*

**Math**

pi radians = 180 degrees so 47.1 deg (pi rad/180 deg) = 0.822 radians

*July 9, 2016*

**Mathematics**

3 pi/9 + pi/9 or pi/3 + pi/9 180/3 + 180/9 60 + 20 80 or simply (4/9)(180) = 80

*July 9, 2016*

**no - supplement**

pi not 2 pi 13 pi/13 - 11 pi/13 = 2 pi/13 so d

*July 9, 2016*

**Calculus**

well, any old plane that is not parallel to the other two will intersect both at a point along the lines of intersection of those planes. The line of intersection will be parallel to the cross product of or two normals i j k 1 1 3 1-1 2 Find a plane that has that line of ...

*July 8, 2016*

**Got to be kidding**

Due to bending in a beam? Due to weight of mass hanging from ceiling by string? Due to compression sound wave in steel bar? Due to cooling of same bar while ends are fixed? etc etc etc etc ........

*July 7, 2016*

**Physics**

force = m g = 8 (9.81) work = potential energy gained = m g h = 8 (9.81)(12) power = work/time = 8 (9.81)(12)/15 If for some incomprehensible reason you really ant power/force, divide 12/15

*July 7, 2016*

**Maths**

amount = original * (1+r)^t 3 = (1+r)^t ln 3 = t ln (1+r) t = ln 3 / ln(1+r) r = .09 t = ln 3 / ln(1.09) t = 1.0986 / .086178 t = 12.74 years ====================== check 3 = 1 * 1.09^12.74 ?????? 3 = 2.997 yes that will do

*July 7, 2016*

**Physics**

u = horizontal speed = 73/3 = 24.3 m/s falls 8 meters in 3 seconds h = Hi + Vi t - 4.9 t^2 0 = 8 + 3 Vi - 9(4.9) Vi = 12 m/s upward speed at tree top of 8 m so let's find the top above that tree v = Vi -9.81 t 0 = 12 - 9.81 t t = 1.22 seconds rising above tree so h at top ...

*July 5, 2016*

**Physics**

find ke before child jumps (1/2)I omega^2 find new I (which you did already) find new omega (which you did already) Find new ke = (1/2) Inew (omega new)^2 now work done = new ke - old ke I went up a little but omega went down so I suspect the work will be negative In other ...

*July 5, 2016*

**been there, done that**

http://www.jiskha.com/display.cgi?id=1467694862

*July 5, 2016*

**Physics**

p = m v Ke = (1/2) m v^2

*July 5, 2016*

**Physics**

Force * time = change of momentum T (7*10^-4) = 2 * 6

*July 5, 2016*

**Physics**

impulse = change of momentum = force * time

*July 5, 2016*

**Physics**

Power * time = change in energy 20 P = m g h = 1800 * 9.81 * 15

*July 5, 2016*

**Physics**

(1/2) m v^2 = m g (45-5) v^2 = 2 (9.81)(40) --------------------------------- Second question has no real answer unless we assume that the potential energy is zero at the ground level. ONLY changes in potential have meaning,and you must always define a base If we ASSUME U = 0 ...

*July 5, 2016*

**Physics**

Maybe assume they both take the same time to stop when they crash into you Force * time = change in momentum for duck Force * time = 2.8 * .35 for goose Force * time = 3.4 * .75

*July 5, 2016*

**Prealgebra/probability**

tails, tails, heads does NOT work H H T H T H T H H Quarter, Penny could be H H H T T H T T that is four, 8 now for each so 32 so I agree

*July 3, 2016*

**physics**

add up the forces. That is one equation add up the torques (moments) about x = 0. That is the second equation

*July 3, 2016*

**physics**

C + W = 926 so 2 W = 1852 - 2 C then (1852 - 2 C) + .6 C = 736 1852 - 736 = 1.4 C etc

*July 3, 2016*

**physics**

190 down at left C up at x = .6 75*9.81 down at x = 1 W up at x = 2 forces up = forces down C + W = 190 + 75*9.81 = 926 Newtons moments about x = 0 sum to 0 -.6 C + 75*9.81*1 - 2 W = 0 or 2W +.6C = 736 Newton meters

*July 3, 2016*

**Physics**

lol, finally 33 * 50 = 12 x x = 33 * 50/12

*July 3, 2016*

**Physics**

so where is the fulcrum?

*July 3, 2016*

**LOL - not enough known**

I do not know either mass or the x of the right hand side

*July 3, 2016*

**Physics**

v = Vi + a t 0 = 30 + a (6) a = -5 m/s^2 ==================== v = Vi - 5 t 0 = 40 - 5 t t = 8 seconds

*July 3, 2016*

**physics**

work = force * distance so how far? assume v =0 at start F = m a 4 = 20 a a = (1/5) m/s^2 v = Vi + a t v = 0 + 3 a x = Xi + Vi t + (1/2) a t^2 x = 0 + 0 + (1/2)(9) x = 4.5 meters so W = F x = 4 * 4.5 = 18 Joules

*July 3, 2016*

**math**

2 (L+w) = 270 L + .75 L = 135 1.75 L = 135 L = 135/1.75 etc

*July 3, 2016*

**math**

a + 3 a = 80 so 4 a = 80 a = 20 etc

*July 3, 2016*

**Math**

b = (5/8) s so g = (3/8) s now g = (3/8) s + 6 and number of students = s + 6 b = 5/8 s = (3/8)s +6 so (2/8)s = 6 s = 24 that was original s s+6 = new total = 30

*July 3, 2016*

**better**

http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/atomic/covalentrev4.shtml

*July 3, 2016*

**CHEMISTRY**

http://search.yahoo.com/yhs/search?p=dot+and+cross+diagram+H2O+bond&ei=UTF-8&hspart=mozilla&hsimp=yhs-001

*July 3, 2016*

**Physics**

find resultant and do the opposite. north 11 + 22 sin 30 east 22 cos 30 magnitude = sqrt(north^2 + east^2) tan angle north of east = north/east you want that magnitude but opposite direction, same angle south of west

*July 2, 2016*

**PHYSICS**

vol = 20 cm^3 ????? Your typing is very confusing then upward force = weight of water displaced (Archimedes) = 10 cm^3 * 1 gram/cm3 * g = 10 grams * g = .010 kg * 9.81 = .098 Newtons upward buoyancy but weight = volume * density * g = 20 * 2.5 * 9.81/1000 = 0.49 N difference...

*July 2, 2016*

**Math**

no if she made 65 out of 100 that will take less than if she made 650 out of 1000

*July 2, 2016*

**Physics**

(1/2) m v2^2 = 1.23 (1/2) m v1^2 so v2 = sqrt(1.23) v1 v2 = 1.11 v1 well, that is an 11% increase

*July 2, 2016*

**Mathematics**

25 letters allowed for first spot 25 for second spot so 625 letter combinations 9 digits 9*9*9*9 = 9^4 so 625*9^4 = 4,100,625

*July 2, 2016*

**physics**

or to do it the physics way: (4585 drops/ft^2)*(1 ft^2/15 tiles) = (4585 drops/ 15 tiles)

*July 2, 2016*

**physics**

4585/15

*July 2, 2016*

**patel**

must be bigger than 1 because 1^2 = 1 must be smaller than 2 because 2^2 = 4 so between 1 and 2 by the way sqrt 3 = 1.732050808 approximately

*July 2, 2016*

**Sciencr**

Yes, hot air holds more water. Fog happens if air saturated with all the moisture it can hold cools down. Similarly if saturated air comes in contact with a cool surface like a basement wall that air cools and the water condenses out. Interestingly by the way, hot water holds ...

*July 2, 2016*

**physics**

Are you sure the captain is a novice? Despite the fact that he will land downstream from his starting point, his fastest path across the water is to head straight across. Anyway I will pretend I am not a navigator and do what your book wants you to do. For example: He could be...

*July 2, 2016*

**gibberish**

please check what you wrote "Earth is 2R times far away from earth " makes no sense to me.

*July 2, 2016*

**physics**

force 1215 m what is that about? Anyway all that matters is depth p = rho g h = 1000 kg/m^3 * 9.81 * 3 = about 30,000 Pascals that is the pressure abouve the one atmosphere at the surface or "gage" pressure. That one atmosphere is about 100,000 Pascals so the total ...

*July 2, 2016*

**Math(Assignment Due**

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

*June 29, 2016*

**Math(Assignment Due**

Google David Lane normal distribution

*June 29, 2016*

**Math**

6*5*4*3= 30*12 = 360

*June 29, 2016*

**Math1**

165 * 1.04

*June 28, 2016*

**Calculus**

x^2 dy+2xydx - 2ydy +(1/xy)(xdy+ydx) = 0 [x^2-2y+1/y]dy + [2xy+1/x]dx = 0 dy/dx = -[2xy+1/x] / [x^2-2y+1/y]

*June 28, 2016*

**Math**

small left ---> large right 5467

*June 28, 2016*

**Probability and statistic**

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

*June 27, 2016*

**physics**

60,000 /3600 = 16.7 m/s 45,000 /3600 = 12.5 m/s v =Vi + a t 12.5 = 16.7 + 10 a a = -0.42 meters/second^2

*June 27, 2016*

**physics**

d = (1/2) a t^2

*June 27, 2016*

**Math**

in the slope/intercept form: y = m x + b m is the slope b is the y axis intercept where x = 0 here the slope is positive 0.5 so the line goes up to the right from the point (0,-2) (and of course down to the left :)

*June 27, 2016*

**Math**

y = 35 + 15 x

*June 27, 2016*

**maths**

(x-3)(3x+2)=0 alpha = 3 beta = -2/3 so (x-9)(x-4/9) = y x^2 -9x -4x/9 + 4 = y y = x^2 - (85/9) x + 4

*June 27, 2016*

**English**

One says "at". I suppose if you live in a tunnel, you eat "in" it :) However is you say: "What about dinner in my house?", You probably mean instead of in my yard or garage.

*June 26, 2016*

**GEOMETRY**

p(a)+ p (b) - p(a and b) 1,2,3,or 4 out of 6 = 4/6 tail = 1/2 = 3/6 4/6 + 3/6 - 2/6 = 5/6

*June 26, 2016*

**GEOMETRY**

prob of first one blue = 5/16 now we have 15 in the bag prob of white = 5/15 = 1/3 so 5/16 * 1/3 = 5/39

*June 26, 2016*

**GEOMETRY**

Hey, it is time you should be able to do these.

*June 26, 2016*

**GEOMETRY**

A and B could be 6 A and C - impossible B and C - impossible

*June 26, 2016*

**GEOMETRY**

the attempts are independent so (3/7)^3

*June 26, 2016*

**GEOMETRY**

2 out of 15 2/15

*June 26, 2016*

**GEOMETRY**

1/16

*June 26, 2016*

**math**

18,000 * 1.07^18

*June 26, 2016*

**GEOMETRY**

p even = 3/6 = 1/2 p A = 1/3 they are independent so 1/2 * 1/3 = 1/6

*June 26, 2016*

**Math**

cos T * sin T = 1/4 so 2 cos T * sin T = 1/2 so sin 2 T = 1/2 thus 2 T = 30 deg or pi/6 radians T = pi/12 radians or 15 deg now cos * sin must be + so T in quadrant 1 or quadrant 3 so actually T = pi/12 or T = 13pi/12 which is 195 deg pi/12 + 13 pi/12 + (2pi+pi/12) = (1/12 +13...

*June 26, 2016*

**Biology**

http://shenndesigns.weebly.com/my-physical-trait---curly-hair.html half of each assuming no one has only a little curly so 4:4

*June 26, 2016*