Friday

September 30, 2016
Total # Posts: 27,213

**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*

**Math**

2(x-4)+y=6 3x-2(y-3)=13 2 x - 8 + y = 6 3 x - 2 y + 6 = 13 2 x + y = 14 3 x -2y = 7 y = 14 - 2x use that 3 x - 2 (14-2x) = 7 3 x - 28 + 4 x = 7 7 x = 35 = 7*5 so x = 5 go back and find y

*February 27, 2016*

**Math**

y= -3/2x-1 which I assume means y = -(3/2)x - 1 so use that 2 [ -(3/2)x - 1 ] - x = -10 -3 x - 2 - x = -10 -4 x = -8 x = 2 etc

*February 27, 2016*

**Physics**

well, you have a + 80 e charge fired at a +1 e charge they repel each other How close will the proton get to the 80 protons? when the kinetic energy of the oncoming proton is used up climbing the potential hill of the 80 protons. it stops and backs away Ke = (1/2) m v^2 ...

*February 27, 2016*

**physics**

No conduction or convection through vacuum, only radiation (use shiny material to reflect)

*February 27, 2016*

**physics**

i = 25/Requivalent = 1 amp so we need Req = 25 In parallel Req = R1R2/(R1+R2) 25 = 50 R2/(50+R2) 25 (50 + R2) = 50 R2 50 + R2 = 2 R2 R2 = 50 which we could have guessed :)

*February 27, 2016*

**PHYSICS**

So where are your answers?

*February 27, 2016*

**MATH**

there are 3 ft per yard there are 9 ft^2 per yard^2 w = (20/3) yards so (20/3) L = 396 L = 3 * 396 / 20 yards multiply by 3 if you want feet

*February 27, 2016*

**Physics**

i = V/R = 12 / .004 amps P = i V = 144/R Joules i = 80 R = V/i = 12/ 80 external resistance Rx = R - .004 power to motor = i^2 Rx = 6400 Rx

*February 27, 2016*

**Figures missing**

Probably F * 49.6 = 1460 * 1.90 but I do not see a figure

*February 26, 2016*

**science**

100 = (1/2) a t^2 so 200 = a (25) a = 8 m/s^2 F = m a = (200/9.81) 8 F = 163 N That is a pretty light bike if it has a rider, perhaps a small child.

*February 26, 2016*

**Stats please help**

5/6 * 5/6 * 5/6 * 5/6 = answer = (5/6)^4 = .482

*February 25, 2016*

**MATH**

yes, although you sure use a lot more steps than I :) -4+1 = -3 -3*4 = -12

*February 25, 2016*

**history**

Now I may explode being from Massachusetts so I think you better Goggle them.

*February 25, 2016*

**Check math please!**

Yes, both right

*February 25, 2016*

**Check math please!**

second one same method 5/9 yes consonant =2/3 so not is 4/9 agree - note I used opposite approach from you, same answers :)

*February 25, 2016*

**Check math please!**

Anna mixes the letters S, E, L, E, C, T, E, and D thoroughly. Without looking, Mary draws one letter. Expressed as a fraction, decimal, and percentage, what is the probability that E will NOT be the letter Mary selects? A. 3/8, 0.375, 37.5% B. 8/5, 1.6, 16% C. 5/8, 0.625, 62.5...

*February 25, 2016*

**we do not have your drawing**

so we do not have the directions of 1 and 2 we know that the total east (x) momentum must be zero and the total north (y) momentum must be zero

*February 25, 2016*

**Math**

8.6 cm ( 50 mi/2 cm) = 215 mi

*February 25, 2016*

**Math**

.15 * 8.25 about .8 + .4 = 1.2

*February 25, 2016*

**Math**

5 * .06 * 2000 = 600 so yes and see you can check it easily :)

*February 25, 2016*

**science help PLS**

I would bet on b but around here the problem is sea gulls

*February 25, 2016*

**Math**

yes, did that a while ago

*February 25, 2016*

**physics**

lets do adolph (1/2) m v^2 = m g h v^2 = 2 g h = 2 (9.81)(.56) so v = 3.31 m/s at push so adolph momentum = 104*3.31 = 345 kg m/s Ed has the same magnitude of momentum 80 V = 345 Ved = 4.31 m/s 4.31^2 = 2 (9.81) (h) h = .9464 m

*February 25, 2016*

**Mathematics**

find slope of tangent dy/dx 2 x + 2 y dy/dx - 2 -4 dy/dx = 0 dy/dx (2y-4) = 4 - 2x dy/dx = (4-2x)/(2y-4) at x = 5 and y = -1 dy/dx = (4 -10)/(-6) = -6/-6 = 1 :) slope of normal = -1/slope = -1 so y = -x + b -1 = -5 + b b = 4 so in the end y = -x + 4

*February 25, 2016*

**Math**

(z - 2 +3i)(z -2 -3i) = 0 commutative property to multiply z (z -2 -3i) = z^2 -2 z -3 z i -2(z -2 -3i) = -2 z + 4 + 6 i 3i(z -2 -3i) = +3zi -6 i + 9 add ------------------------------ = z^2 - 4 z + 13 so a = -4 and b = 9

*February 25, 2016*

**Math**

matrix for reflection over y axis: -1 +0 +0 +1 dilation matrix r r or r r matrix multiplication is not necessarily comutative dilate first r r * x y = r x, r y then reflect rx , ry * -1 +0 +0 +1 = -rx , ry now reflect first -1 +0 |x| +0 +1 |y| = -x , + y now dilate -rx , + r y...

*February 25, 2016*

**linear programming**

c = acres of corn w = acres of wheat constraints: c+w </= 100 graph that line,shade under wheat cost = 20 w corn cost = 40 c 20 w + 40 c </= 2400 graph that line, shade under wheat labor = 4 w corn labor = 16 c 4 w + 16 c </= 800 graph that line, shade under Now the ...

*February 25, 2016*

**Maths**

3 y^2 dy/dx - dy/dx / y^2 = 2 x -7 dy/dx dy/dx (3 y^2 -1/y^2 + 7) = 2 x dy/dx = 2 x /[ 3 y^2 -y^-2 + 7 ]

*February 25, 2016*

**physics**

net north = 8 - 2 = 6 Newtons net east = 6-4 = 2 Newtons |F| = sqrt (36 + 4) = 2 sqrt 10 tan angle n of e = 6/2 = 3 angle n of e = 71.6 degrees north of east or 90 - 71.6 = 18.4 degrees east of north (compass direction)

*February 25, 2016*

**Physics**

mechanical advantage = 13.4/1.34 = 10 weight = 53.4 g = 53.4*9.81 divide by 10 for input force 5.34 * 9.81 = 52.4 Newtons input

*February 25, 2016*

**Physics**

Work = force * distance = 13.4 *30 = 402 Joules (1/2) m v^2 = 402 1.524 v^2 = 804 v = 22.9 m/s

*February 25, 2016*

**MATH PLEASE**

x(5.49) = (5.49 - 2.25) x = .59 59 %

*February 25, 2016*

**MATH PLEASE**

1.4 * 12.95 = 18.13

*February 25, 2016*

**MATH PLEASE**

.52 s = s - 38.87 38.87 = .48 s s = 80.98

*February 25, 2016*

**Chemistry**

N2H4 + N2O2 = 2H2O + 2 N2 limited by .3 mol N2H4 so get .6 mol N2

*February 25, 2016*

**History**

agree, see: http://www.ourdocuments.gov/doc.php?flash=true&doc=21

*February 25, 2016*

**Pre Cal**

assume you mean x^2 + y^2 = 0 That is a circle of zero radius with center at the origin :) In other words a dot at the origin.

*February 25, 2016*

**Science**

Looks like it reacted chemically with something in the air to me :)

*February 25, 2016*

**math**

first one black = 26/52 = 1/2 second one black = 25/51 third one black = 24/50 fourth one black = 23/49 etc until we get to number 12 then multiply all those fractions that means you got every king, queen and jack 4 kings + 4 queens + 4 jacks = 12 of the 52 card 1 = 12/52 ...

*February 25, 2016*

**MATH**

3 x - y = 4 3 x - y = 6 never cross -parallel, no solution 2 x - y = 1 3 x + y = 6 --------------add 5 x = 7 x = 7/5 etc 1 x - 5 y = 5 3 x + 1 y = 7 multiply first by 3 3 x -15 y = 15 3 x + 1 y = 7 ---------------subtract -16 y = 8 y = -1/2 etc

*February 24, 2016*

**Math**

21 * 7 = (1 - 5/8) p = (3/8) p p = 49*8 = 382 pages

*February 24, 2016*

**Algebra**

y = - x^3 no y = -3^x would be but not this

*February 24, 2016*

**Algebra: Check Answer**

LOL no need to ask, plug back in h = -16(10.4)^2 + 156(10.4) +105 = -1730.56 + 1622.4 + 105 = -1730.56 + 1727.4 close enough to the ground :)

*February 24, 2016*

**Math**

Yes dA/dr = 2 pi r = 6.28 r correct however think a little more dA = 2 pi r dr = circumference * dr If you draw a picture of a circle r and then one outside it with radius r + dr You will see immediately that the change in area is the strip of length 2 pi r times the width dr

*February 24, 2016*

**Math**

dA = 2 pi r dr yes, correct however notice that this is simply the circumference the new area added is the circumference * dr

*February 24, 2016*

**math**

Yes we agree but I simplified

*February 24, 2016*

**math**

I assume dy/dx=(4sqrt(y)ln x)/x y^-.5 dy = 4 (ln x /x)dx y^.5 = 2 [ .5 ln^2 x ] y^.5 = ln^2 x y = ln^4 x + c

*February 24, 2016*

**Physics**

bullet momentum = .017 v total mass = .017+1.2 = 1.217 kg final momentum = initial momentum .017 v = 1.217 V' V' = .014 v normal force on table = m g = 1.217 (9.81) friction force = .23*1.217*9.81 = 2.75 Newtons work done = 2.75 *8.6 = 23.6 Joules so 23.6 =(1/2)mV'...

*February 24, 2016*

**Algebra 2**

yes all 3 are correct but it is easier to use sin and cos sin^-1 (3/19) and cos^-1 (18.8/19)

*February 24, 2016*

**ALGEBRA**

surface area = area of top + area of bottom + area of side = pi r^2 + pi r^2 + 2 pi r h = 2 pi (r^2+ r h) = 2 pi r (r + h) = 2 *pi*4 * 10 = 80 pi volume = pi r^2 h = pi *14 * 6 = 84 pi

*February 24, 2016*

**Math**

let z = y^.5 then dz = .5 y^-.5 dy dy = 2 y^.5 dz = 2 z dz 2 z dz /(z cos^2 (z) ) = x dx dz/( cos^2 (z)) = .5 x dx tan z = .25 x^2 + constant tan y^.5 = .25 x^2 + constant

*February 24, 2016*

**Mensuration**

Now I showed you how to do one by subtracting rectangles. You do this one.

*February 24, 2016*

**Math**

That is quite a markup : I have a sneaking suspicion that they mean 140% markup but will do it as stated .75 * price = 39.95 so usual price = 53.27 cost + 2.40 * cost = 53.27 3.40 * cost = 53.27 cost = 15.67 39.95 - 15.67 = 24.28

*February 24, 2016*

**Trigonometry**

m and j tan 30 = m/15 tan 45 = 1 = j/15 j - 15 and m = 15 tan 30 = 8.66 m+j = 23.7

*February 24, 2016*

**Precalculus**

sec 4x = 1/cos 4x I can not graph it for you here but note that cos 90 or pi/2 = 0 so you are going to have a bunch of vertical asymptotes

*February 24, 2016*

**Mensuration**

the original sheet is 30*20 = 600 cm^2 the remaining sheet is 30-8 by 20-8 or 22 * 12 = 264 cm^2 so you removed: 600 - 264

*February 24, 2016*

**Calculus**

pi/3 = 60 degree just so I do not have to use radians on my calculator :) c^2 = a^2 + b^2 - 2 a b cos C get initial stuff first cos 60 = 1/2 sin 60 = .866 c^2 = 64 + 169 - 208 cos 60 c^2 = 233 - 104 = 129 c = 11.4 now do the problem 2 c dc/dt = -208 (-sin 60) dC/dt so dc/dt = ...

*February 24, 2016*

**Math**

i = -75 p^2 + 600 p if p = 3 i = -75 (9) + 1800 1,125 = -75 p^2 + 600 p 75 p^2 -600 p + 1,125 = 0 solve quadratic for 2 values of p. Throw out any negative one etc for max I assume you do not know calculus so complete square to find vertex 75 p^2 - 600 p = -i p^2 - 8 p = -i/75...

*February 24, 2016*

**statistics**

I will do three cards, you do five. 52 cards, 26 are red so find probability of all black first draw 26/52 = 1/2 second draw 25/51 third draw 24/50 = 12/25 prob of all black =.5*25/51*12/25 =.118 so 1-.118 = .882 for at least one red in three draws

*February 24, 2016*

**physics- check this out**

v = Vi + a t v = 0 at stop a = -Vi/t = -35 m/s^2

*February 24, 2016*

**Physics**

7 t = d 13 t = d+42 so 6 t = 42 t = 7 7 t = d = 49

*February 24, 2016*

**physics**

A kilowatt is 1,000 Watts

*February 24, 2016*