Friday

May 27, 2016
Total # Posts: 26,283

**maths**

r = 44/2pi = 7 cm area = pi (49) = 154 cm^2 square side = 11 area = 121 cm^2
*March 11, 2016*

**math and science**

v = Vi + a t 0 = 36 + a t t = -36/a d = Vi t + .5 a t^2 40 = 36 (-36/a) + .5 (a)(36^2/a^2) 40 = - 36^2/a + .5 *36^2/a 80 a = -36^2 a = -16.2 m/s^2 then F = m a = -1500(16.2) Newtons
*March 11, 2016*

**Math**

2 x + y = 320 x y = 12,600 so y = 12,600/x 2 x + 12,600/x = 320 x^2 + 6,300 = 160 x x^2 - 160 x + 6,300 = 0 x = [160+/-sqrt(25600-25200)]/2 x = [ 160 +/- 20] /2 x = 90 or 70 try 90 then y = 140 2x + y = 320 Yes, that works try 70 y = 180 2x+ y = 140 + 180 = 320, Yes that works
*March 11, 2016*

**math**

multiply both sides by -1 (-1)(-y) = + y (-1)(3) = -3 so y = -3
*March 11, 2016*

**math**

2 ends are 16*14 2 sides are 4.8*14 top and bottom are 4.8 * 16 so 2(16*14 + 4.8*14 + 4.8*16)
*March 11, 2016*

**math**

13 + 13 = 26 13 hearts and 13 clubs
*March 9, 2016*

**Math**

y = 10 x + 4 (-2, -16) (-1 , -6) (0 , +4} (1 , 14) (2 , 24)
*March 9, 2016*

**Math**

slope = (-6+1)/(1-0) = -5 so y = -5 x + b 9 = 10 + b b = -1 so y = -5 x -1 or 5 x + y = -1
*March 9, 2016*

**PHYSICS ( PERIODIC MOTION)**

if damping proportional to v F = -kx -bv then x = A e^-(bt/2m) sin w' t five cycles is about 3.67 seconds so 1/2 = e^-(3.67 b /.226) take ln both sides -.693 = - -16.2 b so b = .0427 then w' = sqrt (k/m -b^2/4m^2) = sqrt (73. - .035) =8.542 = 2 pi/T T = .7355 s change ...
*March 9, 2016*

**PHYSICS ( PERIODIC MOTION)**

mass = .1136 kg g = 9.81 m/s^2 so weight = .1136*9.81 = 1.114 Newtons spring constant k = 1.114 N/ .134 meters = 8.32 N/m T = 2 pi sqrt(m/k) = 2 pi sqrt (.1136/8.32) = 0.734 s = 7.34 * 10^-1 s
*March 9, 2016*

**Maths**

(1/2)M + (1/3)M + 40 = M multiply by 6 3 M + 2 M + 240 = 6 M 240 = M spent M-40 = 200
*March 9, 2016*

**Science**

In English units, the acceleration of gravity near the surface of earth is about 32 feet/second^2 = g When we used those units, we defined mass in slugs. mass in slugs m = weight in pounds/g = weight in pounds/32 Then we could use Newton's second law F = m a where force is...
*March 9, 2016*

**Math**

one is 16 * 5 the other is (40 - 5) = 35 *5 so 80 *5 [ 16+35 ] = 80*5*51-
*March 9, 2016*

**Physics**

In English units, the acceleration of gravity near the surface of earth is about 32 feet/second^2 = g When we used those units, we defined mass in slugs. mass in slugs m = weight in pounds/g = weight in pounds/32 Then we could use Newton's second law F = m a where force is...
*March 9, 2016*

**english**

verbs like worked SLOWLY or ate quickly An ly at the end is a dead giveaway but is not always the case.
*March 9, 2016*

**Precalculus quadratic stuff**

Lets complete the square to look at the parabola y = -2x^2+16x+40 x^2 - 8 x -20 = -y/2 x^2 - 8 x = -y/2 + 20 x^2 - 8 x + 16 = -y/2 +36 (x-4)^2 = -(1/2)(y-72) so max area occurs when x = 4 and area = 72 zeros are when x^2-8x-20 = 0 (x-10)(x+2) = 0 or when x = 10 and when x = -2...
*March 9, 2016*

**Math**

25 x >/= 5000 x >/= 200
*March 8, 2016*

**Physics HW Plz help**

the fundamental frequency is called the first harmonic Higher harmonics are integer multiples of the fundamental we know 24/3 = 8 1 f = 8 2 f = 16 3 f = 24 4 f = 32 5 f = 40 6 f = 48
*March 8, 2016*

**Algebra**

LOL, yes, just use a square
*March 8, 2016*

**Physics grade 12**

2/x^2 = 8/(12-x)^2 1/x^2 = 4 /(12-x)^2 4 x^2 = 144 - 24 x + x^2 3 x^2 + 24 x - 144 = 0 x^2 + 8 x - 48 = 0 (x+12)(x-4) = 0 x = 4 cm then 12 - x = 8 cm check 2/16 = 8/64 ??? yes right
*March 8, 2016*

**math**

.06 * 300 = 18 empty (answer) .06 * 310 = 18.6 do not show of the 310 310 - 18.6 = 291.4 show up (answer) additionally 300 seats - 291.4 passengers = 8.6 empty seats which is really 18 empty because 40% of a passenger takes a whole seat
*March 8, 2016*

**math**

.98 * 15,000 = 14,700 Only 2 percent will arrive late so your flight will probably be on time. Of course the key word is "probably" and there is no way you can tell if yours is one of the two out of one hundred that are late.
*March 8, 2016*

**No diagram**

If you tried to copy and paste a picture, that does not work.
*March 8, 2016*

**math**

0.06 * 500 = 36
*March 8, 2016*

**history**

http://en.wikipedia.org/wiki/Afro-Asian
*March 8, 2016*

**math**

20 * 8 = 160 player days 0.80 * 160 = 128 player days or an average of 16 players/day
*March 8, 2016*

**phy 231**

x = 1.5 sin (2 pi * .181 t) = 1.5 sin (1.137 t) v = dx/dt = 1.5* 1.137 cos (1.137 t) v max = 1.5 * 1.137 a = d^2x/dt^2 = -1.5*1.137^2 sin (1.137 t) a max = 1.5 * 1.137^2
*March 8, 2016*

**physics**

surface tension is force/length I am going to call density rho, not P. P is confusing because usually pressure. F = m a = rho L^3 * L/s^2 = rho L^4/s^2 so F/L = rho L^3/s^2 but g is L/s^2 so F/L = rho L^2 g if our length scale is h then Y = F/L = constant * rho h^2 g By the ...
*March 7, 2016*

**math help fast**

http://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html
*March 7, 2016*

**math help fast**

http://www.mathsisfun.com/algebra/sequences-sums-geometric.html
*March 7, 2016*

**math help fast**

2. -4,8,-16,32,... -4 to + 8 is +12 then it goes DOWN 12 so not arithmetic, different d now is it geometric? 8/-4 = -2 -16/8 = -2 32/-16 = -2 = r SO GEOMETRIC next term is 32 * -2 = -64 so the middle one. I do not understand why you are having trouble with these.
*March 7, 2016*

**math help fast**

#1 is Arithmetic with d = 5 It is NOT geometric r = 29/24 = 1.208 r = 19/14 = 1.357 1.208 is NOT 1.357
*March 7, 2016*

**matg**

if in degrees sum of angles in triangle = 180 x - 7 + x + 3 x + 2 = 180 5 x - 5 = 180 5 x = 185 x = 37 x-7 = 30 3x+2 = 113
*March 6, 2016*

**Physics 12**

length on table = x length over side = 2-x mass/meter length = m mass on table = m x max friction force =.5 m g x mass over the side = m(2-x) weight over the side = m g(2-x) if slips when .5 m g x = m g (2-x) x = 2 (2-x) 3 x = 4 x = 4/3 = 1.33 meter = 133 cm
*March 6, 2016*

**physics**

Vi = 36 u = 64 tan A = 36/64 |v| = sqrt (36^2 + 64^2) = 4 sqrt(337)
*March 6, 2016*

**Mathematics grade 9**

regroup to +700 +120 + 3 -200 - 70 - 3 ------------------ +500 + 50 + 0 or 550
*March 6, 2016*

**Networks, Matrices, Linear equations.**

I think the total to X is .2*3000 + .5*2000 + .7*5000 X = |.2 .5 .7 | times the column 3000 2000 5000 so I would write { X Y } column= |.2 .5 .7| |.8 .5 .3| times the column 3000 2000 5000
*March 6, 2016*

**maths**

well their difference is one :) 4 + 5 = 9
*March 6, 2016*

**Physics**

Momentum is conserved period. total kinetic energy conserved? No, where did you get that idea? Think about a bullet hitting a block and getting embedded. I am sure you have done that for homework. You solve it using conservation of momentum. However (1/2)m V^2 of bullet is not...
*March 5, 2016*

**science**

with a simple pendulum period of pendulum = 2 pi sqrt (L/g) ------------------------ with a scale Using a 1 kg weight force down on scale = m g in Newtons, weight = mass in kg * g so g in m/s^2 = weight in newtons / mass in kg Of course your scale is likely to show kilograms ...
*March 5, 2016*

**physics**

If those are at consecutive corners, they cancel each other.
*March 5, 2016*

**Physics**

net force up = 800- m g
*March 5, 2016*

**Algebra**

halfway between 1/2 and 1/10 is (.5 + .1)/2 = .3 = 3/10 not 1/6
*March 5, 2016*

**Algebra**

1/10 = 3/30 1/6 = 5/30 ---------- subtract d = -2/30 = -1/15 check it first two points d = 5/30 - 15/30 = -10/30 = -1/3 This is not an arithmetic progression, typo.
*March 5, 2016*

**trigonometry**

You fly on a "heading" not a "bearing". You take a "bearing", the direction of something, like a lighthouse, from you. Mathematicians are terrible navigators. That said: 60 deg 20' = 60.33 degrees clockwise from North which is 29.67 above +X ...
*March 5, 2016*

**math**

x (x-3) is supposed to be negative if x >3 it is positive if x <0 it is positive it is only positive * negative = negative between 0 and 3
*March 4, 2016*

**math**

Do I get extra credit for finding a harder way ?
*March 4, 2016*

**math**

cos x/sin x + sin x/(1+cos x) = 0 ?? nah, maybe you mean (1+cos x)/sin x + sin x/(1+cos x)=1 (1+cos)(1-cos)/(sin(1-cos)) +sin (1-cos)/[(1+cos)(1-cos)] = 1 (1-cos^2)/(sin-sin cos) + (sin-sin cos)/(1-cos^2) = 1 sin/(1-cos) + (1-cos)/sin = 1 sin^2 + (1-cos)^2 = sin(1-cos) (1-cos^...
*March 4, 2016*

**physics**

It has to get 40 m high when it gets 40 m high, it must have a centripetal acceleration of 1 g or it no longer touches its track. so Ac = v^2/r = 9.81 m/s^2 v^2 = 20*9.81 v = 14 m/s now it has to drop a distance m g h = (1/2) m v^2 to the TOP of the wheel h - 40 = .5 v^2/g but...
*March 4, 2016*

**Physics**

normal force = m g cos 26.8 so friction force = .26 m g cos 26.8 force down slope = m g sin 26.8 so m g sin 26.8 - .26 m g cos 26.8 = m a a = g [ sin 26.8 - .26 cos 26.8]
*March 4, 2016*

**Math**

the area of a cube divided by the volume? 6/s did you use a + where it should have been = ? area of sphere divide by volume ? 3/r area of right circular cylinder divided by volume ? 2/h + 2/r = 2 (r+h)/rh
*March 4, 2016*

**Sorry, all I have time for**

That is all I can try tonight.
*March 3, 2016*

**calculus**

b) Let z = x + iy. Obtain the real and imaginary parts of the function f(z) = 1/(1+z) I assume f(z) = 1/[(1+x) +iy ] = [(1+x)-iy] / {[(1+x) +iy ][[(1+x)-iy] } = [(1+x)-iy] /{(1+x)^2 +y^2} = (1+x)/{(1+x)^2 +y^2} - i y /{(1+x)^2 +y^2}]
*March 3, 2016*

**calculus**

T is theta z = r e^iT = r (cos T + i sin T) z^3 = r^3 e^3iT = -1 if r = 1 e^3 i T = -1 = cos 3T + i sin 3T 3T can be pi or 3 pi or 5 pi so T = pi/3 or pi or 5 pi/3 so z = e^i(pi/3) or e^i(pi) or e^i(5 pi/3) for pi/3 z = cos pi/3 + i sin pi/3 = .5 + .866 i for pi z = -1 (well ...
*March 3, 2016*

**Physics**

angular momentum before =I w=.19 * .0684 + .486(.418)^2*0 = .013 new I w = (.19 +.085)w so .013 = .275 w w = .047 rad/s
*March 3, 2016*

**Weight Is Force! Science**

where it has a mass of 390000 N that is a typo should be where it has a WEIGHT of 390000 N m g = w 9000 g = 390,000 g = 390/9 = 43.3 m/s^2
*March 3, 2016*

**physics**

Ac = v^2/r v increases but there is no radial force so v^2/r has to be the same so r has to increase.
*March 3, 2016*

**No**

I choose 2 2+4 is LESS than 7
*March 3, 2016*

**Math**

y = 3 x y = x^2 y = sin x then relations that are not functions y^2 = x or y = x^(1/2) two values of y for every x y = sin^-1 (x) for every x there is an infinite number of y values like if x = 1/2 y = 30 deg, y = 150 degrees etc x y 1 -1 0 0 1 1
*March 3, 2016*

**Math**

well, 2 a b = 0 so either a = 0 or b = 0 or both :) b ) let me see 5 - 5 = 0 I think true c) I suppose so d) sure n/1
*March 3, 2016*

**Math**

(52 g/85 cm) 10 cm = 6.12 g
*March 3, 2016*

**Math**

find probability that all are green first one 4/9 second one 3/8 third one 2/7 all green = (4/9)(3/8)(2/7) answer = 1 - that result ============================= find probability that 9 of 9 are red find probability that 8 of 9 are red that sum is the probability that zero or ...
*March 3, 2016*

**Physics**

weight = 7 * 9.81 Newtons force down slope = weight * sin 30 = (1/2)weight force up slope = 381 N net force up slope = 381 -(1/2) weight = 347 N a = F/m = 347/7 = 49.5 m/s^2 v = 5 + a t v = 5 + 49.5 t distance = average speed * t 9 = (1/2)(v+5) t 18 = (10+49t) t 49 t^2 + 10 t...
*March 3, 2016*

**physics**

power = work/time since the time is the same, the power ratio is the work ratio work in = kinetic energy out kinetic energy proportional to v^2 [ like (1/2)m v^2 ] v'^2/v^2 = 16
*March 3, 2016*

**math**

1/3 of a pint = 1/3 of 1/2 qt = 1/6 qt or 1/3 of 2 cups = 2/3 cup 1/3 pint * (1 gal/8 pints)(1 barrel/55 gallons = 1/(3*8*55) = 1/1320 barrels :) or whatever
*March 3, 2016*

**PHYSICS HELP**

(a) m g = 9.81 * 4.5 = 44.15 N (b) 44.15 cos 12 (c) 44.15 cos 25 (d) what else is new?
*March 3, 2016*

**Biology**

1. Well, wet salt is heavy :) 2. Thirsty? replenishes electrolytes lost during workout?
*March 3, 2016*

**Math**

If T is each term in the sequence T1 = (3*1-2)^2 = 1^2 = 1 T2 = (3*2-2)^2 = 4^2 = 16 T3 = (3*3-2)^2 = 7^2 = 49 T4 = (3*4-2)^2 = 10^2 = 100 then the sums are S1 = 1 S2 = 1+16 = 17 S3 = 17 + 49 = 66 S4 = 66 + 100 = 166
*March 3, 2016*

**Advanced Algebra**

which by the way is what Olaf said :)
*March 2, 2016*

**Advanced Algebra**

arithmetic sequence a = 30,000 d = 2,300 n = 10 sum n = 1 to n = 10 of a + d(n-1) http://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html = 10/2 (60,000 + 9 * 2,300)
*March 2, 2016*

**Math**

x >/= 4 or you will be taking the square root of a negative number
*March 2, 2016*

**algebra**

True, but you would probably figure out feet 499.2 /12 = 41.6 feet = 41 feet 7.2 inches
*March 2, 2016*

**gibberish**

costs nothing for the first 6 days,t = 0 through 5 ? c(t) = 5+1 ??? no t, does not makes ense
*March 2, 2016*

**typo**

What do you mean it has and "overcome"? efficiency maybe ? if it were perfect then V2/V1 = F1/F2 = 3/2 = 1.5 but if efficiency is only .6 then we really must lift 30/.6 = 50 N with 20 N so we need a ratio of 5/2 = 2.5
*March 2, 2016*

**math**

x + (x+50) = 540/2 = 270 2 x + 50 = 270 2 x = 220 x = 110 x+50 = 160
*March 2, 2016*

**CHEM QUESTION**

S is easier to work with than S8 If you really want to know how many mols of S8 you used, multiply S and the rest of the balanced equation by 8 by 8 Here is the long answer:-) http://www.ibchem.com/faq/2008/09/18/what-is-the-molecular-formula-of-sulphur/
*March 2, 2016*

**Chemistry**

P1 V1/T1 = P2 V2/T2 = n R T1 = 0 +273 = 273 T2 = 25 + 273 = 298 P2/P1 = T2/T1 = 298/273 The other questions are the same deal.
*March 2, 2016*

**PHYSICS**

let speed = s u = s cos 30 Vi = s sin 30 = s/2 v = s/2 - g t = s/2 - 9.81 t so 0 = s/2 - 9.81 t at the top where v = 0 so t = s/(2*9.81) 2 t = time in air = s/9.81 range = u * time in air 5.90 = s cos 30 * s/9.81 s^2 = 9.81 *5.90 /cos 30 so s = 66.8 meters/second now do it for...
*March 2, 2016*

**Physics**

cool the 100 g soup 10 degrees from 50 to 40 warm the x g water 35 deg from 5 degrees to 40 deg heat out = .8 * 100 * 10 heat in = 1.0 * x * 35 so 35 x = 800 x = 22.8 g which is 23 to your rough significant figures
*March 2, 2016*

**huh**

You do not have time in your equation, only a solid unmoving cosine function. Do you mean t instead of x ? y = .4 cos[ (2 pi/3) t ] + 1.2 ? if so then dy/dt = v = -.4(2 pi/3) sin[ (2 pi/3) t ] a = d^2y/dt^2 = -.4(2 pi/3)^2 cos[ (2 pi/3) t ] which is a = - (2pi/3)^2 * y
*March 1, 2016*

**Math**

10 * 10 * 10 = 1,000
*February 29, 2016*

**Physics**

Perhaps there is a pulley and block B is hanging ? call tension in line = T T = 2.25 (g-a) Static friction force = .2(4.5+mc)g so T - .2 (4.5+mc)g = (4.5+mc) a so 2.25 (g-a) -.2(4.5+mc)g = (4.5+mc)a Now in PART A a = 0 2.25 g -.2(4.5+mc)g = 0 2.25 = .9 + mc so mc = 1.35 Kg...
*February 29, 2016*

**physics**

force = F F sin 15 = F up F cos 15 = F horizontal = F normal to wall friction = mu F cos 15 up total up= F sin 15 + .275 F cos 15 Fdown = m g = 5*9.81 = 49 Newtons so F (sin 15 + 0.275 cos 15) = 49
*February 29, 2016*

**Physics**

noe, 2223 Joules is right bUT m g h = 2223 75 * 9.81 * h = 2223 h = 3.02 meters
*February 29, 2016*

**Math Algebra PLEASE EXPLAIN**

2500 * 12 / 600 = 25 * 2 = 50 :)
*February 29, 2016*

**Global Studies**

Iran, Iraq, Turkey, ...... There is no such place officially but usually you think of the Middle East East of Egypt. Use Google.
*February 29, 2016*

**Social Studies**

I might add that they are likely to travel a lot, be nomads, because they will run out of food for them and their animals quickly in one spot.
*February 29, 2016*

**Math!**

I would be inclined to say it is not 3/17 because that is a ratio of whole numbers not sqrt 25 because that is 5 not 0.666.... because that is 2/3 which is a ratio of whole numbers so lo and behold, you are correct :)
*February 29, 2016*

**Physics**

friction force up slope = .27 * m * 9.81 * cos 25 = 2.40 m gravity component down slope = m * 9.81 * sin 25 = 4.15 m net force down slope = 4.15m -2.40m = 1.75 m Newtons Now you can do the problem F = m a = 1.75 m so a = 1.75 m/s^2 down plank 3 = (1/2) a t^2 6 /1.75 = t^2 t = ...
*February 29, 2016*

**Physics**

mass m weight = m g = 9.81 m friction force = 0.1 * weight = 0.981 m That is the entire horizontal force so F = m a 0.981 m = m a a = 0.981 ------------------- how long to stop? v = Vi - 0.981 t 0 = 7.6 - 0.981 t t = 7.75 seconds to grind to a halt d = Vi t - (1/2)(0.981) t^2 ...
*February 29, 2016*

**Physics**

agree with 2223 Joules m g h = 2223 75 * 9.81 * h = 2223 h = 3.02 meters
*February 29, 2016*

**You there? You get it ?**

got it ?
*February 29, 2016*

**Physics**

1. Whatever Pe he had up on that board relative to the water surface is all Ke when he hits the water. Ke = (1/2) m v^2 = (1/2) (75) (7.7)^2 Joules THAT is the Pe he had up on the board :) 2. NOW YOU ARE ON A ROLL Pe = m g h = answer to #1 above :)
*February 29, 2016*

**Geometry**

Atta go :)
*February 29, 2016*

**Geometry**

hope you got 17 :)
*February 29, 2016*

**Geometry**

Pythagoras says: L^2 = h^2 + b^2 = 225 + 64
*February 29, 2016*

**physics**

58 cm = .58 m F = k Q1 Q2 / (.58)^2
*February 29, 2016*

**physics**

http://www.pha.jhu.edu/~broholm/l24/node1.html
*February 29, 2016*

**physics**

when 4 t = 2 pi we have gone around the circle from t = 0 so 4 T = 2 pi T = 2 pi / 4 = pi/2
*February 28, 2016*

**Chemistry**

http://www.youtube.com/watch?v=MKLi-V0CY9M
*February 27, 2016*