Monday

January 16, 2017
Total # Posts: 28,762

**wrong salt percent**

Seawater is about 3.5 not 35 percent salt .035 * 1000 = 35 grams salt and 1000 - 35 grams H2O

*October 26, 2016*

**Math**

You are welcome.

*October 26, 2016*

**Math**

yes, it is not only irrational but imaginary yes, the second one is rational You can always write a number with repeating decimals as a ratio of whole numbers

*October 26, 2016*

**Physics (Mechanics)**

do it for 1/4 of mass on one tire F = m v^2/r = mu m g where m = 905/4

*October 26, 2016*

**Geography**

Migration means something else entirely to me. When I hear the word I do not think of permanent immigration or emigration but of the old as the human race tension between settled city and town and farm dwellers and tough herders and hunters following the seasons and their game...

*October 25, 2016*

**Physics**

a = drop in potential energy = m g h b = gain in kinetic energy = (1/2) m v^2 work done by friction = a - b

*October 25, 2016*

**Algebra 1**

just subtract, term by term 4 x^3 2 x^2 2 x 0 4x^3 + 2 x^2 + 2 x 2 x (2 x^2 + x + 1)

*October 25, 2016*

**Math**

10 (0.1 x) = 10 (6550) so x = 65,500

*October 25, 2016*

**Math Help**

5^5/5^2 = 5^5 * 5^-2 a^b *a^c = a^(b+c) so we have 5^(5-2) = 5^3 yes

*October 25, 2016*

**Math Help**

yes ANYTHING^0 = 1

*October 25, 2016*

**Math**

35000 = a (1.07)^6 so a = 35000 / (1.07)^6

*October 25, 2016*

**maths**

6.35228 to one figure should this be 6 or 7 ? well 3 is less than five so 6 to two figures should this be 6.3 or 6.4? well 5 anything is more than halfway to the next digit so 6.4 to three figures should this be 6.35 or 6.36? well 2 is less than 5 so 6.35 to four figures ...

*October 25, 2016*

**Math generic rectangles**

this is to get 7 * 12 one rectangle is 7 by one and the other is 7 by 11. They attach together to get 7 by 12 but it is easier to multiply 7 by 1 and 7 by 11 than to multiply 7 by 12 directly. It is really just the distributive property a(b + c) = ab + ac

*October 25, 2016*

**physics projectile**

Oh, range d = 20 cos 30 * 20 = 400 * .866

*October 25, 2016*

**physics projectile**

horizontal problem: u = 20 cos 30 the whole time d = u T vertical problem: Vi = 20sin 30 = 10 v = Vi - g t at top v = 0 g t = 10 t = 10/9.81 or about one second to top time of flight = 2t = about 2 seconds h = Vi t - 4.9 t^2 = 10(1) - 4.9 = about 5 meters

*October 25, 2016*

**Physics Help!**

initial x momentum = .46 m initial y momentum = 0 final x momentum = .37 m cos 37 + v m cos T final y momentum = .37 m sin 37 - v m sin T so .46 = .37 cos37 + v cos T and .37 sin 37 = v sin T

*October 25, 2016*

**Physics**

how high was she above the bottom of the swing? h = 30 (1-cos 37) m g h = (1/2) m v^2 = initial Pot energy = final kinetic energy 2 * 9.81 *30 (1-cos 37) = v^2 ================================ add (1/2)(4^4) to initial energy for part 2

*October 24, 2016*

**Physics**

Ke up top = 1/2*.25 *225 gain of Pot energy = .25*9.81*1.2 work input = (1/4)(2 pi *.6)*30 so sum of those 3 energies = (1/2)(.25)v^2

*October 24, 2016*

**Math**

I bet you mean: 3x/(x^2-x) which is 3/(x-1) the denominator is zero if x = 0

*October 24, 2016*

**Math**

k x^2 -3k x - 2 = 0 a = k b = -3k c = -2 look at b^2 - 4 a c look at parabola y = 9k^2 + 8 k must be 0 or + for 0 k (9k+8) = 0 k = 0 or k= -8/9 between them, y is negative SO k</= -8/9 or k>/=0

*October 24, 2016*

**Math**

(x+5)/(y+5) = 2/3 (x-5)/(y-5) = 3/7 ------------------ ------------------ 2 y + 10 = 3 x + 15 3 y - 15 = 7 x - 35 ------------------------ ------------------------ 3 x - 2 y = -5 7 x - 3 y = 20 ---------------- ----------------- 9 x - 6 y = -15 14 x -6 y = 40 ----------------...

*October 24, 2016*

**Maths**

r = 55/2pi big area = pi (r+3.5)^2 little area = pi (r)^2 subtract

*October 24, 2016*

**maths**

b^2-4ac says it all in (a) for example 36-4(21) is negative so sqrt of negative in sollution so complex roots (b) 36 + 4(21) is + so real roots (c) x^2 + x/25 = 0 x(x+1/25) = 0 x = 0 or x = -1/25 (d) ?

*October 24, 2016*

**maths**

x = 15/7 y = 4/7 z = -40/7

*October 24, 2016*

**maths**

http://www.gregthatcher.com/Mathematics/GaussJordan.aspx for the first one for example there are three rows and four columns 1 +1 +1 -3 1 -1 -2 13 1 +0 -4 25

*October 24, 2016*

**physics**

That is correct assuming that the ball is sliding, not rolling. If rolling there is a force back on the bottom of the ball to give it angular acceleration but I suspect you have not covered that. Let's just assume that is a net force of 3 N :) In other words the 3 N is the...

*October 24, 2016*

**Algebra**

150 miles /30 miles/gal = 5 gal

*October 24, 2016*

**I need help, I'm stuck...what is the correct answe**

There are 14 students 7 got less than 7.5 and 7 got more than 7.5 so 7.5 is median for mean 2(4)+2(5)+1(6)+2(7)+3(8)+4(10) =102 102/14 = 7.3

*October 24, 2016*

**American Government**

no taxes no army see: http://americanhistory.about.com/od/governmentandpolitics/f/articles_of_confederation_fails.htm

*October 24, 2016*

**maths**

divide 6 by 2 and square it, 9 x^2 - 6 x + 9 -9 (x-3)^2 - 3^2 3(x^2 + 20 x/3) (10/3)^2 = 100/9 3 [ x^2 + 20/3 x + (10/3)^2 - (10/3)^2 ] = 3 [ (x-10/3)^2 - (10/3)^2 ]

*October 24, 2016*

**physics**

gravity force down slope = m(acceleration down slope) m g sin 37.5 =(m v^2/r) cos 37.5 g tan 37.5 = v^2/r v^2 = r g tan 37.5 = 394*9.81 tan 37.5 v = 54.5 m/s

*October 23, 2016*

**advanced math**

16 + 169 = 185 = x^2 so x = square root of 185 = 185^0.5 = 13.6

*October 23, 2016*

**Math**

11/15 = .73 10/13 = .77 better

*October 23, 2016*

**Math**

legs = 4 p + 2 c = 52 p+c = 22 so p = 22-c 4(22-c) + 2 c = 52 88 - 2 c = 52 2 c = 36 c = 18 then p = 4

*October 23, 2016*

**Geometry**

tan 75 = 80/d d = 21.4 ft between buildings tan 62 = x/21.4 x = 40.3 = height abobe 80 so 120 ft

*October 23, 2016*

**Physics**

a = .09/480 = 9/48000 m/s^2 dv = a dt = (9/48,000) *7d/w*24h/d*3600s/h = 113 m/s we are assuming constant mass. Possibly fuel or even engine components were ejected. This is just the speed change due to the propulsion. Presumably there are also gravitational forces acting even...

*October 23, 2016*

**Physics**

energy stored in spring = (1/2) k x^2 = (1/2)(100)(.04) work done by friction = mu m g *d so 50*.04 = .2 * 1 *9.81* d solve for d

*October 23, 2016*

**math**

If they were 1 by 1 the diagonal would be 400 say n of them along each side diagonal is then n sqrt 2 =400 n = 400/sqrt 2 but n^2 is number of squares so answer = 400^2/2 =200*400 = 80,000 I suspect you mean the diagonal is 80 cm, not 800 by the way

*October 23, 2016*

**Math**

df = 4 dx so if you go from 3 to 2.9 that is dx = -.1 so df = -.4 and 5 - .4 = 4.6 sure enough

*October 23, 2016*

**EASY MATH FOR 4TH GRADE**

or 5 (3*1000 + 3*100 + 3*10 * 3*1) 15*1000 + 15*100 + 15 * 10 + 15*1 1*10,000+5*1000 + 1*1000+5*100 + 1*100+5*10 + 1*10 + 5 10,000 + 6,000 + 600 + 60 + 5 16,665 again I do not know how you are doing this in your class but suspect distributive property in some form.

*October 23, 2016*

**EASY MATH FOR 4TH GRADE**

5( 3000 + 300 + 30 + 3 ) 15,000 + 1,500 + 150 + 15 15,000 + 1,500 + 165 15,000 + 1,665 16,665

*October 23, 2016*

**Calculus**

x = 5 + 20 t y = -75 + 15 t z =distance =sqrt(25+5625) (I bet you meant 7.5 miles but oh well) dx/dt = 20 dy/dt = 15 at t = 0 x = 5 and y = -75 z^2 = x^2 + y^2 2 z dz = 2x dx + 2 y dy so dz = (x dx + y dy)/z and dz/dt = (x dx/dt + ydy/dt)/z = (5*20-75*15)/sqrt(25+56250

*October 23, 2016*

**Physics need R**

angular momentum of disk = (1/2) M R^2 omega final angular momentum of debris initial = m R^2 (v/R) = m v R so m v R = (1/2) M R^2 omega omega = 2 v (m/M) /R

*October 23, 2016*

**Chemistry (atoms)**

1 mole of water H2O has one mol of O so we have .0595 * 6.022*10^23 atoms

*October 23, 2016*

**MATH**

A = x y 50 x + 20 (2y) = 2000 or 5 x + 4 y = 200 5 x + 4 A/x = 200 5 x^2 - 200 x - 4A = 0 where is vertex of parabola? -b/2a = 200/10 =20 so x = 20 5(20) + 4 y = 200 4 y = 100 y = 25

*October 23, 2016*

**Physics**

s = speed 45.9 = u T where u = s cos 40 so T = 45.9 /(s cos 40) where T is time aloft rise time is half T or t = T/2 v = Vi - g t Vi = s sin 40 at top v = 0 s sin 40 = 9.81 t = 9.81[45.9/(2s cos 40] or 2 s^2 sin 40 cos 40 = 9.81*45.9 remember trig now

*October 22, 2016*

**physics**

m a = G m Mmoon /R^2 so 1.62 = G Mmoon/(1.738*10^6)^2

*October 22, 2016*

**Physics**

assume you mean cross product no what if they are perpendicular ?

*October 22, 2016*

**physics**

force = rate of change of momentum which is m a if the mass is constant 10 Newtons = change of momentum/0.10 second so change of momentum = 1 kg m/s by the way the change in speed would be 1/5 = .2 m/s

*October 22, 2016*

**questions all the same**

water density, rho, is about 1,000 kg/m^3 the mass of a column of water one square meter in cross section and h meters high is therefore: mass = rho * 1 * h = 1,000 h kilograms the weight of that mass is mg = 1,000 * 9.81 * h Newtons the pressure is that force over the one ...

*October 22, 2016*

**hold it**

Bob seems to be using vi both for vertical and horizontal speed I think in fact the original vertical speed is zero so h = Hi + 0 -4.9 t^2 1.8 = 21.9 - 4.9 t^2 t^2 = 4.1 t = 2.03 seconds to fall now the car has to go horizontal 58 meters in 2.03 seconds so I will call the ...

*October 21, 2016*

**solve what for t?**

Is it something like sin t = .5 or something?

*October 20, 2016*

**physics need asap help**

initial x momentum = m u initial y momentum = 2 m v final x momentum = 3 m (2) cos 37 final y momentum = 3 m (2) sin 37 so u = 6 cos 37 v = 3 sin 37

*October 20, 2016*

**physics need help**

integral of F(x) dx = a x^2/2 + b x^3/3 at 3 this is 9a/2 + 27b/3 at 1 it is a/2 + b/3 subtract 8a/2 - 26b/3 now put in a and b 40/2 + 52/3 etc

*October 20, 2016*

**history**

d is politically incorrect so you better pick c a is pretty funny as is b

*October 20, 2016*

**Algebra 2**

You can easily check this yourself. First 3 + 6 + 2 = 11 sure enough twice as many peanuts as almonds, yes total cost = 1.5*6 + 3*3 + 1.5*2 = 9 + 9 + 3 = 21 so yes, done

*October 20, 2016*

**Math**

takes time t for pump 1 the big one takes time 3 t for pump 2 so pump 1 does 1/t jobs/hr pump 2 does 1/3t jobs/hr (1/t + 1/3t) = 4/3t jobs/hr together (4/3t jobs/hr)9hr = 1 job 12 hours = t

*October 20, 2016*

**PHYSICS- PROJECTILE MOTION**

Your teacher is really trying to get to you with this separation of constant horizontal speed from increasing vertical speed. 89 * 3.10 centimeters if you really mean cm/s

*October 20, 2016*

**Pre algbra**

-20/30 - 9/30

*October 20, 2016*

**PHYSICS- PROJECTILE MOTION**

a) Trick question - it does not change. u = 1.90 b) v = -9.81 t so |v| = 9.81 (0.410) c) speed = sqrt (u^2+v^2) d) tan (angle down from horizontal) = |v|/u

*October 20, 2016*

**physics**

sqrt(9+4)

*October 19, 2016*

**Calculus**

line is y = -5 x + 3 so slope = -5 = slope of tangent f' = slope = 6 x - 7 where is that -5? 6 x - 7 = -5 6 x = 2 x = 1/3 so y = 3(1/9) -7(1/3) + 4

*October 19, 2016*

**History**

World War One?

*October 18, 2016*

**Physics**

Violet bends more than red the slower wavelength bends more so violet is slower

*October 18, 2016*

**nobody knows**

the other two sides must also have lengths.

*October 18, 2016*

**Physics**

f = sqrt (T/[m/L]) / 2L m = 8000 A L so 170 = sqrt (T/8000A)/4 680 = sqrt (T/8000A) also 1% = .01 = T/ (E A) so T/A = .01 E so 680 = sqrt (.01 E/8000) 462400 = .01 E/8000 E = 3.7 *10^11

*October 18, 2016*

**physics**

20 = (1/2)10 t^2 solve for t = 2 seconds d = 15 t =15*2 = 30 m

*October 18, 2016*

**physics**

The total momentum of the system can not change if there is no external force. Therefore 4

*October 18, 2016*

**Math Question**

parabola, not a line, because y is squared

*October 17, 2016*

**Math**

12 a + 8.5 s = 10,175 a+s = 950 so s = (950-a) 12 a + 8.5(950-a) = 10,175 12 a + 8075 - 8.5 a = 10,175 3.5 a = 2100 a = 600

*October 17, 2016*

**Math**

4x*1 = 4x

*October 17, 2016*

**math**

4x = 50 x = 12.5

*October 17, 2016*

**Algebra**

10x+4

*October 17, 2016*

**History**

How about basic language (Indo European) ?

*October 17, 2016*

**Engineering**

ABS density varies from 1.0 to 1.4 grams/cc you did not give any units except dollars .437 what? grams, pounds, kg , oz ?

*October 17, 2016*

**Nobody knows**

we do not know how much plastic each part takes

*October 17, 2016*

**Math**

21/4 + 41/16 is 84/16 + 41/16 your turn now

*October 17, 2016*

**math**

her speed = v current speed = 3 time up = 18/(v-3) time down = 18/(v+3) so 18[ 1/(v-3) + 1/(v+3) ] = 8 [ 1/(v-3) + 1/(v+3) ] = 4/9 [ v + 3 + v - 3 ] = (4/9)(v^2-9) 18 v = 4 v^2 - 36 2 v^2 - 9 v - 18 = 0 v = 6 for positive v root ----------------------------- check up speed = 3...

*October 17, 2016*

**Physics**

more like 12.7 did you take the square root? I think not :)

*October 17, 2016*

**Physics**

(1/2) v^2 = 9.81 (8.2) v^2 = 16.4*9.81

*October 17, 2016*

**math**

pi r^2 h = 25 so h = 25/(pi r^2) A = 2 pi r^2 + 2 pi r h but we know h(r) A = 2 pi r^2 + 2 pi r * 25/(pi r^2) A = 2 pi r^2 + 50/r r better be >0

*October 17, 2016*

**math**

he has made .4*20 = 8 of 20 he shoots total of 20 + x shots 8 + x = .5(20+x) 8 + x = 10 + .5 x .5 x = 2 x = 4 ==================== check he has now shot 24 and has made 8+4 = 12 sure enough 12/24 = .5

*October 17, 2016*

**math**

fewer dollars per oz or per pound is cheaper per pound of weight gained.

*October 17, 2016*

**Math**

1.5+1.2 = 2.7

*October 17, 2016*

**Maths**

How many do you think? Draw a picture.

*October 17, 2016*

**maths**

there are 2 pi radians in a circle C = 2 pi R so (2.5/2pi)(2 pi R) = 2.5 R = 2.5 * 8 = 20

*October 17, 2016*

**algrebra**

-6x = 2 x = -2/6 = -1/3

*October 17, 2016*

**Math**

1 1/2 = 3/2 (3/2)(42) = 3 (21) = 63

*October 17, 2016*

**I don't either**

I could say 7 + 31 + 6 = 44 low or 8 + 32 + 7 = 47 high but that would be kind of silly and I would be more likely to estimate using nearest whole numbers 8 + 31 + 7 = 46

*October 17, 2016*

**math**

L + w = 250 so L = 250-w L = 50 + w so 250 - w = 50 + w 2 w = 200 w = 100 L = 150

*October 17, 2016*

**Math**

LOL, ok dividing by 3 is the same as multiplying by 1/3 :)

*October 17, 2016*

**Math**

huh?

*October 17, 2016*

**Math**

(9/5)/3 = 3/5

*October 17, 2016*

**Math**

(-11/8)(14/5) = - (11/4)(7/5) = 77/20 = 3 17/20

*October 17, 2016*

**Math**

1.5 + 1.2

*October 17, 2016*

**8th pre algebra**

By the way that is algebra, not pre algebra :)

*October 17, 2016*

**8th pre algebra**

2(10) - 7 = ? sure enough 13 so you are right BUT actually you ADDED 7 to both sides

*October 17, 2016*

**Trig**

2sin 2Tcos2T/[1 + 2 cos^2 2T -1] = sin 2T cos 2T/ [cos 2T cos 2T] = sin 2T/cos 2T = tan 2T = 2 tan T/[1-tan^2T]

*October 17, 2016*

**math**

6.60/[12*710] or 9.18/[24*500] which is less dollars per mL ?

*October 17, 2016*