Sunday

October 23, 2016
Total # Posts: 27,530

**Social Studies**

Did historical Japan have good roads? Did the Incas? How were each governed? How did they communicate with other nations?

*October 16, 2016*

**Math**

g = number of girls 5g/7 = number of boys g - 5g/7 = 120 2g/7 = 120 g/7 = 60 g = 420 then boys = (5/7)420 = 300 and 420 + 300 = 720 total

*October 16, 2016*

**chemistry**

Do you mean in catalytic converter? Maybe read "types" section in here: http://en.wikipedia.org/wiki/Catalytic_converter

*October 16, 2016*

**Math**

using common denominator of 18: 10/18 , 7/18 and 9/18 Now you rearrange them.

*October 16, 2016*

**physics**

2.9*9.81 Newtons

*October 15, 2016*

**chemistry**

A certain wavelength or frequency corresponds to a certain photon energy which is a certain change of energy of the electron shell around the atom. In other words the frequency tells you how an electron orbit changed.

*October 15, 2016*

**calculus**

dh/dt = -9.8 t + 10 when t = 1 dh/dt = 10-9.8 = 0.2

*October 15, 2016*

**math**

x y change in y/change in x which is slope -2 9 ****** -5 -1 4 ****** -5 0 -1 ****** -5 1 -6 ****** -5 2 -11 hmmm, constant slope = -5 y = -5 x + b 9 = -5 (-2) + b 9 = 10 + b b = -1 so y = -5 x -1 answer check at last point -11 = -5(2) -1 -11 = -10 - 1 yes, good

*October 15, 2016*

**Cousino**

speed upstream = 8 - u speed downstream = 8 + u time upstream = 5/(8-u) time downstream =5/(8+u) so 5(8-u) + 5/(8+u) = (4/3) hr 5(8+u) + 5(8-u) = (4/3)(64-u^2) 15(8+u) + 15(8-u) = 256(64-u^2) etc, solve quadratic

*October 15, 2016*

**be careful with parentherses**

do you mean 1/(2a) or (1/2)a 1) f(-2) = 4 a^2 +2a + 3b = 4 a^2-b+8 f(-3) = 9 a^2 +3a + 3b = 7a^2-b+14 so 2 a + 3 b = - b + 8 2 a + 4 b = 8 a + 2 b = 4 or a = 4 - 2 b and then 2 a^2 + 3 a + 4 b = 14 2(16 - 16 b +4b^2) + 3(4-2b) +4b=14 32 -32b +8b^2+12 -6b +4b = 14 30 + 8b^2 -...

*October 15, 2016*

**physics**

v = velocity up = 30 sin 30 - 9.81 t u = velocity horizontal = 30 cos t if t = 1 v = 15 - 9.81 u = 30(.866) speed = sqrt (u^2+v^2) tan angle up = v/u

*October 15, 2016*

**math**

as y--->0 cos y = 1 - y^2/2 + ........ numerator: 2 - 1 +(1/2)(9)x^2 -1 +(1/2)(16)x^2 0 + (25/2)x^2 oh my now divide by x 25 x/2 goes to 0 as x goes to 0

*October 15, 2016*

**math**

by the way tangent of small angle approaches sine of that small angle :) theta + theta^2/2 .......

*October 15, 2016*

**math**

Hey, I did the other one, try series approach on this one too.

*October 15, 2016*

**math**

m = math only s = science only b = both = 10 31 = m + b = m + 10 so m = 21 s+b = 36 - m s + 10 = 36 - 21 s + 10 = 15 so = Answer all science students s = 5 only science ======================== check 21 + 10 = 31, yes all math students 5 + 10 = 15 , yes all science students 21...

*October 15, 2016*

**Pre-calculus**

This is what it is about: http://www.youtube.com/watch?v=zw0waJCEc-w sin 45 = (1/2)sqrt 2

*October 15, 2016*

**Pre-calculus**

well, 7 = 6 + 1 so it is really sin (6 pi/12 + pi/12) sin(a+b) = sin a cos b + cos a sin b (just like your other problem) sin 6 pi/12 = sin 90 = 1 cos pi/12 = cos 15 deg cos 90 = 0 so cos 15 degrees

*October 15, 2016*

**Math**

y = k/x^3 new y = k/(x/2)^3 = 8 k/x^3 8 times as big

*October 15, 2016*

**english**

I have made 100 ship models in my life. I had made 100 ship models when they told me to stop and start doing physics problems.

*October 13, 2016*

**Maths**

9 km/(3/2)hr = 18/3 = 6 km/hr

*October 13, 2016*

**Math- Please check my answer!**

6/8 = 60/80 8/10 = 64/80

*October 13, 2016*

**Math**

2 driveways/day * 5 d/w = 10 driveways/week 10 driveways/week * 50 work weeks/yr = 500 driveways/year Now as Myah said, what is the question?

*October 13, 2016*

**physics**

heat of fusion * 150 g + 150 * heat capacity* (T-0) = 300 * heat capacity*(50-T)

*October 13, 2016*

**Physics**

normal forces 5 kg block: 5(9.81) 10 kg block 5*9.81 and 15*9.81 forces 5 kg block .2 * 5 * 9.81 right T left no acceleration so T = .2 * 5 * 9.81 = 9.81 N (answer to part C by the way) 10 kg block T left .1 * 15 * 9.81 left 45 N right so 45 - 9.81 - .1*15*9.81 = 10 a the end

*October 13, 2016*

**physics**

h = 1 = (1/2)(9.81)t^2 (a)solve that for t, the fall time u t = 1.5 (b)so u = 1.5/t v = g t = 9.81 t speed = sqrt (u^2+v^2) tan angle below hor = |v|/u

*October 13, 2016*

**8th Grade Math**

y = k x -12.5 = 50 k -25 = 100 k k = -1/4 y = -x/4 y = - (47/4) / 4 = - 47/16

*October 12, 2016*

**math**

(5)(3/13) - 2(10/13) = -5/13 You better stay away from this game. There are 13 cards in each suit of which 3, the jack, queen and king are winners. The other 10, ace through 10, are losers

*October 12, 2016*

**Physics**

If it is moving to the left, the frictional force is pushing right. 0.6 * 90 * 9.81 yes, looks about right but stick to 3 significant figures.

*October 12, 2016*

**algebra**

(0,13) (13,0) and (0,0) completes triangle that is half a 13 by 13 square area = 169/2

*October 12, 2016*

**environmental science**

Ah, almost but your understanding of feedback is backwards. Negative feedback means the output is fed back and inhibits further growth in the output, stable Positive feedback means the output is fed back and INCREASES growth in the output, UNSTABLE. This is what they are ...

*October 12, 2016*

**environmental science**

well, I guess natural gas is higher quality than most of what you find in a landfill :) It all depends on their definition of "near" the surface though.

*October 12, 2016*

**History**

LOL - yes, stamps and tea are different from each other.

*October 12, 2016*

**Physics**

total energy at top = (1/2)(1530)(36) + 1530(9.81)(115) total energy at bottom = (1/2)(1530)(27)^2 work done = energy at top - energy at bottom average velocity = (27+6)/2 time = 4400/average velocity power = work done/time

*October 12, 2016*

**Statistics**

binomial distribution p(n,k) = C(n,k)p^k (1-p)^(n-k) p(3,1) = C(3,3) .38^3 * .62^0 = 1 * .38^3 * 1 do c next because b is 1 - c p(3,0) = 1 * 1 * .68^3 now b = 1 - c = 1 - .68^3

*October 12, 2016*

**Science**

The word "compound" is a dead giveaway.

*October 12, 2016*

**Physics**

ice is about 2.03 Joules/ gram deg c so 2030 J/kg deg c 1.2 kg *2030 J /kg degC (-15-T) = 20,000 J

*October 12, 2016*

**Physics**

v cos 30 = 110

*October 12, 2016*

**Chemistry**

.37* 500 = .96 x where x is the amount of strong stuff you put in 500 - x is the amount of water

*October 12, 2016*

**Science**

which answer uses the word "compound"?

*October 12, 2016*

**Math. please help**

-1/2 = -3/6 +1/3 = 2/6 does that help ?

*October 12, 2016*

**Differential Calculus**

find radius of surface as a function of height h r/h = 5/10 = .5 then surface area = pi r^2 = pi (.25 h^2) change in volume dv = surface area * dh dv = pi (.25 h^2) dh and dv/dt = .25 pi h^2 dh/dt 4 = .25 pi (9) dh/dt solve for dh/dt

*October 11, 2016*

**algebra 1**

50 mi/h * 5280 ft/mi *1 h /3600 s mi cancels h cancels we are left with 50 * 5280/3600 ft/s = 73 ft/s

*October 10, 2016*

**error !**

french alone = f history alone = h both = 8 f+8 - 10 = h+8 or f-h = 10 and f+h + 8 = 40 or f+h = 32 so 2f =42 f = 21 h = 11 so f+8 = 29 study french or both h+8 = 19 study history or both

*October 10, 2016*

**Venn Diagram**

french alone = f history alone = h both = 8 f+8 - 10 = h+8 or f-h = 8 and f+h + 8 = 40 or f+h = 32 so 2f =40 f = 20 h = 12 so f+8 = 28 study french or both h+8 = 20 study history or both

*October 10, 2016*

**American Governement**

I would be inclined to favor A, balance of power.

*October 10, 2016*

**American Governement**

Yes, right, A

*October 10, 2016*

**Chemistry**

.12 * 207 grams

*October 10, 2016*

**value**

(1/2)(100)(64) Joules

*October 10, 2016*

**Chemistry**

LOL, not observable I am sure h/(mv) = 6*10^-34 / (.05*40)

*October 10, 2016*

**Math**

Two problems: 1. x-8 -15 = -6 2. -x+8 -15 = -6

*October 10, 2016*

**algebra**

3000 = 1000 e^10 k 3 = e^10k ln 3 = 10 k solve for k n = 1000 e^5k with same k do e^5k on your calculator

*October 10, 2016*

**social studies**

They are in it !!!

*October 10, 2016*

**Math/ Algebra**

I did not miss a sign. 1/3x is not x/3

*October 10, 2016*

**Math/ Algebra**

well, if it is actually 14 = (1/3) x + 5 or 14 = (x/3)+ 5 then that is 14 = (1/3)27 + 5 14 = 9 + 5 yes however 14 is not 1/ (3*27) + 5

*October 10, 2016*

**Math**

m marbles in bag 2m/5 are red so 3 m/5 = b+y m = r + b + y b/y = 5/7 or y = 7b/5 3 m/5 = b + 7b/5 3 m/5 = 12 b/5 4 b = m b = (1/4) m

*October 10, 2016*

**physics**

I gave you the frequency and the rotational speed because I do not know what "rotational frequency" means.

*October 10, 2016*

**physics**

v^2/r = 6 m/s^2 so v^2 = 86.5 *6 v = sqrt (86.5*6) T = pi d /v = pi(173)/sqrt(86.5*6) f = frequency = 1/T omega = 2 pi f = 2 pi/T = 2 sqrt(86.5*6) / 173

*October 10, 2016*

**Science**

no F = m a big F is big m times big a

*October 10, 2016*

**TECH ED HELP**

I agree with kara.

*October 10, 2016*

**Math**

agreed on the first 2, there is no answer for number 2 but the third 2y = 2x-6 y = x-3 slope = 1 your -3 is b in y = m x + b, the y axis intercept

*October 10, 2016*

**Calc I (@Reiny)**

Reiny already did this for you. Yes, right.

*October 10, 2016*

**physics**

vertical force = m g - F sin 38 horizontal force =.42*vertical force - F cos 38 when the horizontal force is zero, it is about to accelerate so when F cos 38 = .42 (85*9.81-F sin 38) solve for F

*October 10, 2016*

**math**

3/24 = 1/8 = .125

*October 10, 2016*

**Statistics**

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

*October 9, 2016*

**ashworth**

Google subjunctive of was: http://www.google.com/search?q=subjunctive+of+was&ie=utf-8&oe=utf-8 he approves not we approve

*October 9, 2016*

**computer**

LOL, this depends on the level of detail. I am not going to do an entire flow chart for Turbotax deluxe :)

*October 9, 2016*

**chemistry**

to raise the temperature of 1 kg of Aluminum one degree centigrade you must put in 900 Joules of heat energy.

*October 9, 2016*

**math(Quantitative) ...Pls help me**

(b) maybe time of year, exchange rate for currency

*October 9, 2016*

**math(Quantitative) ...Pls help me**

well, your guess is as good as mine but (a) number of football games, depth of snow (b) Legon Ghana? (c) number of hurricanes in past 12 months, number of arrests of bank officers (d) month of the year, number of weddings scheduled for week

*October 9, 2016*

**Maths**

(1/2) g/cm^3 or 500 kg/m^3

*October 9, 2016*

**chemistry**

http://www.google.com/search?q=ch3oh+lewis+structure&ie=utf-8&oe=utf-8

*October 9, 2016*

**math**

pi/2 3 pi/2 and I suppose -pi/2 -3 pi/2

*October 9, 2016*

**math**

so she buys all red ribbon ! 20/1.59

*October 9, 2016*

**Physics**

zero, it came back

*October 9, 2016*

**physic**

.5 (840)(T-16) = 2(4200)(25-T)

*October 9, 2016*

**Physics**

zero Displacement is a VECTOR this ball moved up, then down. It therefore moved zero meters in no direction. They did NOT ask for DISTANCE

*October 9, 2016*

**Math**

C(16,4) = 16! / [ (16-4)!(4!) ] =16*15*14*13/(4*3*2) = 4 * 5 * 7 * 13 = 1280 Oh well

*October 9, 2016*

**math**

21/2 = 10.5 so try 10 + 11

*October 9, 2016*

**physics**

143 = m g + m a = m (9.81+0.762) m = 143/(9.81+.762) weight = m g

*October 8, 2016*

**physics**

g(Re/r)^2 = (1/4)(9.81)

*October 8, 2016*

**physics**

6.5 * 10^5 I expect you mean and 1.8*10^7 F = m a 6.5 * 10^5 = 1.8*10^7 a a = 3.61*10^-2 m/s^2 90 km/h (1 h/3600s)(1000 m/km) = 25 m/s v = a t 25 = 3.61*10^-2 t t = 6.93 *10^2 s = 693 s = 11.5 min

*October 8, 2016*

**Interferometry carried to an unimaginable (for me) extreme **

You better Google LIGO, but that is the whole thing. There is no simple reply really.

*October 8, 2016*

**physics**

6 g - T = 17 a T - mu(11 g) = 11 a what is a? d = (1/2) a t^2 1 = (1/2)a(1.48)^2 a = .913 m/s^2 6 g - T = 15.5 so T = 6 g - 15.5 so 6 g - 15.5 - 11 g mu = 10.0 let g = 9.8 and solve for mu

*October 8, 2016*

**Math**

LOL, cost / number of sprays

*October 8, 2016*

**physics**

vertical: Ftop = mg + Tt = m v^2/R Fbot = Tb-mg = m v^2/R so max is Tb = m g + mv^2/R so mg +Tt = Tb-mg 2 mg = Tb-Tt LOL, could have guessed Horizontal T = m v^2/R given Tb = 1.066 T mg + mv^2/R = 1.066 mv^2/R g = .066 v^2/R so v^2 = g R /.066

*October 8, 2016*

**Maths**

one at x = 0 then 10 more at 5, 10, 15, 20, 25 , 30, 35, 40, 45, 50 You always have one more fence post than panels of fencing

*October 8, 2016*

**Maths**

50/5 + 1 = 11 (one is at x = 0)

*October 8, 2016*

**Social Sudies**

fishing if the ^%$&* feds would let you fish.

*October 8, 2016*

**physics**

I do not see the figure but am at a loss to understand how the ledge has anything to do with it unless he hits it. u = 17 m/s until splash Vi = 0 h = 7.9 m h = 4.9 t^2 so t = 1.27 seconds v = 9.81 t = 9.81*1.27 = 12.5 m/s speed = sqrt (17^2 + 12.5^2)

*October 8, 2016*

**precalculus**

T = 3 so f = 1/T = .333 Hz omega = 2 pi f = 2.09 radians/s at t = t0, d = -10 Amplitude = 10 d = -10 cos [ omega (t - t0) ] that is -10 when t = t0

*October 8, 2016*

**Marbles**

26 in bag both times 10/26 * 7/26

*October 8, 2016*

**Stats**

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

*October 8, 2016*

**physics**

5*4*4 = 80 6*3*3 = 54

*October 7, 2016*

**Calculus - Approximation**

y = x^(1/3) dy/dx = (1/3) x^-(2/3) at x = 1, y = 1 and dy/dx = (1/3)=m y = 1 + (1/3) (x-1) y = (1/3) x + 2/3 at x = 1.1 y = (1/3)(1.1) + 2/3 y = (1/3) 3.1

*October 7, 2016*

**physics**

north speed = Vn = 150 cos 35 east speed = Ve = 150 sin 35 + 26 speed = sqrt (Vn^2+Ve^2) heading = tan-1(Ve/Vn)

*October 7, 2016*

**huh?**

If you are a multiple of ten you are not a prime number. 30 = 3 * 2 * 5

*October 7, 2016*

**Units?**

130 POUNDS and 49 kg ? I think not

*October 7, 2016*

**Physics**

PE = m g h same m so same gh h = (9.8/3.7)5 in feet

*October 6, 2016*

**Physics**

Well, sort of, but in fact momentum is not conserved in this collision. The first law, conservation of momentum, applies ONLY if there is no external force. That is not the case here. The ground exerts a FORCE on the ball, changing its momentum from +mv to -mv Force = rate of ...

*October 6, 2016*

**physics**

call mass m and not 13.9 to save work, it cancels (1/2) m v^2 = retarding force * d (1/2)m v^2 = .122 m g d (1/2)(1.81)^2 = .122(9.81) d solve for d

*October 6, 2016*