Friday

December 2, 2016
Total # Posts: 28,237

**Maths (really hard)**

what is length AB? sqrt(4+ 64) = sqrt 68 = 2 sqrt 17 so length AC = sqrt 17 what is slope AC? It is -1/slope AB slope AB = -2/8 = -1/4 so slope AC = 4 now point C (x,y) Oh, wow, problem over go right one from A go up 4 from there what is hypotenuse? LOL sqrt 17 !!!! so x = 1...

*November 1, 2016*

**Maths (done question a but cant do b)**

-2 + -3 = -5 -5/2 = -2.5 which is y of C 4 ) 6 = 10 10/5 = 5 which is x of C so C(5, -2.5) now AC dx = 5-4 = 1 dy = -2.5 - -3 = .5 d^2 = 1+.25 now CB dx = 6 -5 = 1 dy = -2 - -2.5 = .5 d^2 = 1 + .25 the same

*November 1, 2016*

**LOL - so what is C (?,?)**

Do I have to do part a too ?

*November 1, 2016*

**maths**

change in y = 6 - (-3) = 9 change in x = 7 -4 = 3 so d = sqrt (81 + 9) = sqrt (90) = 3 sqrt 10

*November 1, 2016*

**Math**

You are welcome.

*November 1, 2016*

**Math**

85% = 85/100 = 0.85

*November 1, 2016*

**Calculus**

You are welcome.

*November 1, 2016*

**Calculus**

Sometimes conventional obscurity is insufficient and extraordinary efforts must be made to confuse the student. One seemingly simple but surprisingly effective technique is to reverse the usual roles of x and y.

*November 1, 2016*

**Calculus**

yes it is. Perhaps you are misled by the x being the independent variable instead of y When y = 1 x = 1^3 = 9 (1)^2 + 5 = 1 - 9 + 5 = -3 sure enough now the problem dx/dx = 1 = 3 y^2 dy/dx - 18y dy/dx 1 = (3y^2-18y)dy/dx dy/dx = 1/ (3*1^2 -18*1) dy/dx = 1/(-15) = -1/15 amazing...

*November 1, 2016*

**Science**

well, probably there was air and water in it and the air expanded in the heat pushing the water out.

*October 31, 2016*

**Math**

4 * 7 * 25 = 100 * 7 = 700

*October 31, 2016*

**chemistry**

pentaamminesulfatocobalt (III) bromide http://seattlecentral.edu/faculty/dwick/CC%20name.pdf 1L is the one, NH3 and SO4 reversed

*October 31, 2016*

**Physics**

I am going to assume a flat and earth and the sun at infinity :) In that case the tip of the hawk's shadow is directly under the hawk and moves at the hawk's horizontal speed. u = 6.09 cos 78.6

*October 31, 2016*

**physics**

2 pi radians in 332 sec so omega = angular velocity = pi/166 Ac = omega^2 r = (pi/166)^2 * 2870

*October 31, 2016*

**Science**

Hey, come on, if you reverse the direction of the current you reverse the direction of the magnetic field produced !

*October 31, 2016*

**Physics**

8 north and 2 east so sqrt(64+4) tan angle north of east = 8/2 = 4 3 + 8 + 5 = 16

*October 31, 2016*

**Calculus**

C = 2 pi r so r = 35/pi so dC = 2 pi dr so dr = dC/ (2 pi) = .9/(2pi) a = pi r^2 da = 2 pi r dr da = 70 pi dr da/a = 70 pi dr/a multiply by 100 to get percent

*October 31, 2016*

**4th grade math**

1) right, like 18 does not work 2) n = 12 * x*y*z*.... so n = 2 * 6 * x*y*z*....

*October 31, 2016*

**Calculus**

let z = t^2-1 then dz = 2 t dt or dt =dz/(2 t) and we have integral of t z^(1/3) dt = t z^(1/3) dz/(2t) = (1/2) z^(1/3) dz Got it :)

*October 31, 2016*

**chemistry**

maybe this would help? http://www.coursehero.com/file/p6s4k6su/Bis-ethylenediamine-More-Nomenclature-Feen-2-NO-2-2-2-SO-4-Bisethylenediamine/

*October 31, 2016*

**Physics**

if t is RISE time and Vi is initial speed up v = Vi - 9.81 t at top v = 0 so Vi = 9.81 * 36.761/2 (because it spends half the time going up) Now I hope you know 45 degrees gives max range New Vi = Vi sin 45 U = Vi cos 45 with new Vi find time to top same way 9.81 t = Vi time ...

*October 31, 2016*

**Math**

two circles of radius 6 in, any bigger will not fit. circle area = 2 (pi 6^2) = 72 pi rectanglearea = 12 * 24 waste = 12 *24 - 72 pi

*October 31, 2016*

**Applied math**

5 - (-2) = 5 + 2 = 7

*October 31, 2016*

**Pre Algebra**

d = 2 a d = 34 34 = 2a 34/2 = a a = 17

*October 31, 2016*

**algebra 2**

210 = 4 (v+w) 210 = 6 (v-w) 105 = 2 v + 2 w 105 = 3 v - 3 w 315 = 6 v + 6 w 210 = 6 v - 6 w --------------------add 525 = 12 v etc

*October 31, 2016*

**Science**

V = i R if V increases and i is the same, R must have increased. right

*October 31, 2016*

**Science**

second one is right

*October 31, 2016*

**Science**

NO F = G M m /R^2 more mass is more gravitational force it remains in orbit because the centripetal force is also proportional to mass m v^2/R

*October 31, 2016*

**Physics 11 urgent Steve, bob, damon pls**

PS Perhaps you missed that word "frictionless" Do not think you are pushing that box along a hockey rink. That requires friction and cleats on your shoes if on ice. If no cleats, if the box goes one way you go the other :)

*October 30, 2016*

**Physics 11 urgent Steve, bob, damon pls**

Before the push, the momentum of the system was zero so since there is no EXTERNAL force on the student/box system, After the push the total momentum of the system is zero. Therefore If the student goes North then The box goes South if north is + .8 (30) + v (20) = 0 v = -.8(...

*October 30, 2016*

**Calc.**

perimeter = 2 x + 2 y cost = c = 14 x + 4 y = 15400 or 7 x + 2 y = 7700 y = -3.5 x + 3850 A = x y = x(-3.5 x + 3850) = -3.5 x^2 + 3850 x dA/dx = -7x +3850 zero when x = 3850/7 etc

*October 30, 2016*

**Calculus AB**

f(6) = f(7) + f'(7) * (6-7) f(6) = 34 + 4 (-1) f(6) = 30 not 42 so I disagree

*October 30, 2016*

**Calculus AB**

dC/dx = change of totsl cost per change of number og bikes if dx = 1 then dC/dx = cost of that one cost of 2 more is about 2 dC/dx when x = 40 bu you better also have C(40) :) LOL, total cost goes negative for large number of bikes, very good deal

*October 30, 2016*

**Calculus AB**

A = .5 b h but b = h A = .5 b^2 dA = .5 * 2 b db dA/dt = 2 b db/dt = 14 db/dt

*October 30, 2016*

**Calculus AB**

0 = 0 + Vi(4) - 4.9 (16)

*October 30, 2016*

**Calculus AB**

potential energy at 40 m = m g h = 9.8 m *40 potential energy at bottom = 0 kinetic energy at 40 m = (1/2)m *25 kinetic energy at bottom = (1/2) m v^2 so (1/2) v^2 = 9.8(40) + 12.5 v^2 = 9.8*80 + 25

*October 30, 2016*

**physics**

at top force to left from wall = Fxt vertical force from wall = 0 at bottom Force up from floor = Fzb max force to right from floor =Fxb = .4 Fzb Gravity force down at 10 meters from base = 750 N not accelerating so Fzb = 750 Fxb = .4(750) so Fxt also = .4(750) but to left ...

*October 30, 2016*

**Physics**

LOL - trick question energy is conserved if the ball is caught at the same height as it left the foot, the speed is the same. 19 m/s same horizontal component (of course) same vertical component but down not up (conservation of energy)

*October 30, 2016*

**university physics**

If it was at rest and there is no EXTERNAL force then: total x momentum = 0 total y momentum = 0

*October 30, 2016*

**US History**

State names usually have some historical significance, named after a native American chief or tribe (eg Massachusetts) or Historical Leader (Viginia for virgin queen Elizabeth or Pennsylvania for William Penn etc) or place where some settlers came from (New Whatever)

*October 30, 2016*

**Physics**

1 cm^2 = 10^-4 m^2 delta L = L F/(EA) .005 = 20 /(E*10^-4) E = 4*10^7 Pascals Think material is like rubber or you have a typo.

*October 28, 2016*

**Algebra**

worker 1 does job in x hours worker 2 does it in x+1 hours worker 1 is x hr/job or (1/x) jobs/hr worker 2 is x+1 hr/job or 1/(x+1) jobs/hr time for both together is two hr so [(1/x)jobs/hr + 1/(x+1) ]2hr = 1job 1/x + 1/(x+1) = .5 (x+1) + x = .5 x(x+1) 2x + 1 = .5 x^2 + .5 x .5...

*October 28, 2016*

**Calculus**

first do x components 3(-3) + 2(5) = -9 + 10 = 1 now y components 3(7) + 2(1) = 21 + 2 = 23 < 1, 23 >

*October 28, 2016*

**Math practice test**

The one on the lower left :)

*October 28, 2016*

**Math**

girls = g boys = 1.25 g g + 1.25 g = 450 2.25 g = 450 g = 200 then boys = 250 so there are 50 more boys than girls

*October 28, 2016*

**Physics**

I guess the wires have equal area A delta L = L * F/(EA) same for each so F/E must be the same for each F1/4 = F2/2 F1 = 2 F2 now moments about distance x from left where m is hung F1 * x = F2 (1.5-x) 2 F2 x = F2(1.5-x) 3 x = 1.5 x = .5 meters

*October 28, 2016*

**math**

one electrician would take 18 * 35 = 630 days so 28 electricians would take 630/28 = 22.5 days

*October 28, 2016*

**Algebra**

yes, difference is 1/8 or .125

*October 28, 2016*

**physics**

v = omega r = 3 so omega = 3/2.2 I = m r^2 = 46 * 2.2^2 L = I omega = 46 * 2.2^2 * 3/2.2 = 46 * 2.2 * 3

*October 28, 2016*

**physics**

change in rad/s = 1150 revs/min /1s = 1150 rev/min * 1 min/60 s * 2pi rad/rev /1 s

*October 28, 2016*

**Biomechanics**

h = 0 + 2.5 t - 4.9 t^2 0 = 0 +2.5 t - 4.9 t^2 4.9 t^2 - 2.5 t = 0 t (4.9 t - 2.5) = 0 t = 2.5/4.9 at max height, half that time h = 2.5(1.25/4.9) - 4.9(1.25/4.9)^2

*October 28, 2016*

**history**

yes, more people allowed to vote = more democracy

*October 27, 2016*

**Chemistry**

C2H2 is 26 g/mol (2*12 + 2*1) so 23/26 mols twice that many mols H20 at 18 g/mol (46/26)18 = 31.8

*October 27, 2016*

**Chemistry**

we need 3 mol of C for each of SiO2 we do not have them so only 3.6/3 = 1.2 mol of SiO2 reacts with 3.6 of C that has 2.4 mol of O or 2.4 mol of CO

*October 27, 2016*

**math**

1.20 * 88,000

*October 27, 2016*

**math**

n n+1 n+2 n+3 ------ add 4n+6 = 5 n n = 6

*October 27, 2016*

**math**

the volume of anything pointy at the to with straight sides is area of bottom * height / 3 1.476^2 * 10^6 * 2.17 +10^2 / 3 about 1.0 *10^8 but use calculator

*October 27, 2016*

**Math (Derivative)**

f(x+h) = x+h - 1/(x+h) f(x) = x - 1/x -------------------subtract h - 1/(x+h) + 1/x divide by h 1 - 1/(xh+h^2) + 1/xh 1 +[ - xh +xh+h^2]/(x^2h^2+xh^3) 1 + h^2/(x^2 h^2 + x h^3) 1 + 1/(x^2 + xh) let h --->0 1 + 1/x^2

*October 27, 2016*

**physics**

I = m r^2 omega = v/r I omega = m v r = 1400 * 28 * 116

*October 27, 2016*

**Physics**

momentum before = 45(3.4)+46(4) momentum after = (91)v so 91 v = 45(3.4)+46(4)

*October 27, 2016*

**physicsforce * time = change of mpmentum (called impulse)**

F (1.17) = 40.2(-1.84) ON her so she pushes the wall (Newton's third law) equal and opposite (40.2)(+1.84)/1.17

*October 27, 2016*

**Math (Limits)**

so put in ln .01 and ln .00001 etc or say j = ln z e^j = z e^j = 0 + a little e^-oo = 1/e^oo --->0 + a little

*October 27, 2016*

**physics**

No way I am going to just say what the answer is. You have to know and it is in your text or in any online definition of mechanical work done. Try to answer.

*October 27, 2016*

**math**

89 is a prime number. Therefore you can not do better than simply 89/100

*October 27, 2016*

**Math**

0 = 16 t^2 - 112 t - 480 0 = t^2 -7 t - 30 0 = (t-10)(t+7) t = 10 the other root was before it was launched

*October 27, 2016*

**Math (Fraction Word Problem)**

(3/5) / 2 = 3/10 is exactly the same as (3/5)(1/2) = 3/10 multiplying by 1/2 is dividing by 2 ================================== details: (3/5) / 2 multiply by 5/5 = 5(3/5)/[5*2] = 3/10 or (3/5)(1/2) multiply by 5/5 3/10

*October 27, 2016*

**math**

18000 = (250/2) h so h = 144 now you can find length of OW or IA easily as hypotenuse of right triangle of height 144 and base 25 call that center intersection C triangle OIC is similar to triangle WAC (isoceles with same top angle) so all sides are in the same ratio of 100/...

*October 27, 2016*

**time speed and distance**

distance: a t (a+b)(t-p) (a+2b)(t-p-x) all the same :) at = at + bt -ap -bp so bt = ap + bp at = at -ap -ax+2bt-2bp-2bx (a+2b)x = -ap+2bt-2bp x = (-ap+2bt-2bp)/(a+2b) = (-ap+2ap +2bp-2bp)/(a+2b) = ap/(a+2b) whew !

*October 27, 2016*

**Mathematics**

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

*October 26, 2016*

**Algebra 1**

yes

*October 26, 2016*

**physics**

They are running together at the same velocity. ZERO You and the hunk of earth you are on are zooming through space. What is your velocity relative to your chair if you are sitting quietly on it?

*October 26, 2016*

**Physics**

a = (8-0)/5 = 8/5 m/s^2 F = m a = 150 * 8/5 = 240 Newtons

*October 26, 2016*

**Typos?**

impulse = change of momentum = 8 (2 - -2) = 8*4 = 32 kg m/s none of above, even units are no impulse which is force times time - Newton seconds or momentum change kg m/s

*October 26, 2016*

**Physics**

+ 2 to - 2 = 4 8*4 = 32

*October 26, 2016*

**oceanography**

(1/2)(1/2)(1/2) = 1/8 so 70/8 grams

*October 26, 2016*

**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*