Thursday
December 8, 2016

Posts by Damon

Total # Posts: 28,449

Physics - studying for finals
for the second part, out in a phase angle .05 sin[(2pi/.75)(x+.375t) -PHI] (2pi/.75)(0.50) -PHI = 0 PHI = 2 pi (.5/.75)
December 8, 2016

Physics - studying for finals
A =0.0500 m L = 0.750 m T = 1/5 = 0.2 goes .75 m in .2 s so v=.75/2 = .375m/s for constant phase (x+vt) the+vt makes it left to make it go 2pi for every wavelength l or time T sin [2 pi (x+vt)/L] now the size .05 sin[(2pi/L)(x+vt)] more numbers in .05 sin[(2pi/.75)(x+.375t)]
December 8, 2016

Math
(x-1)(3x-2)(x-4i) but (x-4i)is not allowed alone, we also need its complex conjugate (x-1)(3x-2)(x-4i)(x+4i) I get 3x^4-5x^3+50x^2-80x+32
December 8, 2016

Math
8x + x = 9 x = 63 x = 7 so 8x = 7*8 which is about 56 as I remember.
December 8, 2016

physics
v = g t = 9.81 * 10 = 98.1 if no air drag but with friction terminal speed is 21 so 21 m/s
December 8, 2016

Math
x = -2 is a vertical line through the point (-2,0). Y can be anything.
December 8, 2016

Math (optimization) really confused
three fences of length x two fences of length y A = xy = 225 so x = 225/y p = total length = 2y + 3 x we want to minimize p p = 2 y +3(225/y) dp/dy = 0 at max or min dp/dy = 0 = 2 -675/y^2 2 y^2 = 675 y^2 = 337 y = 18.4 x = 225/18.4 so what is 2y+3x?
December 8, 2016

History Please Help
They were people, humans.
December 8, 2016

Physics
F * 0.24m = 31Nm so F = 31 Nm/0.24m
December 8, 2016

Physics
try throwing something up and see if time stops and moved backwards while the object falls back down.
December 8, 2016

what do you think ?
The force on this object is F = - m g so a = -g What are your answers?
December 8, 2016

Physics
v = Vi +a t 30 = 10 + 2 t t = 10 seconds but your answers are about distance d = Vi t + (1/2) a t^2 d = 10(10) + 10^2 = 200 m
December 8, 2016

Physics
You are welcome. Remember that figure skater spinning slowly with arms extended, then suddenly speeding up when she pulls her arms in :)
December 7, 2016

Physics
Ip = I of platform =(1/2)(95)(2.4^2) Angular momentum = Ip(2.3) IT STAYS THAT FOREVER New In = Ip +30*(2.4^2) In omega = Ip (2.3) omega = (Ip/In)(2.3) (Part a) b) Her I = mr^2 is zero BACK to original I and 2.3 rad/s c) (1/2) In omega^2 - (1/2)Ip(2.3^2)
December 7, 2016

physics
You are welcome.
December 7, 2016

physics
200 food calories for a half cup so 400 for a whole cup 400 cal (4184 J/cal) = 1,673,600 J watts = 1,673,600 J/600 s = 2789 Watts which is 3.74 hp
December 7, 2016

Physics
height above bottom call it h h = 33(1-cos 31) initial energy = m g h speed at bottom = sqrt(2gh) because (1/2)mv^2 = m g h for part b initial energy = m g h +(1/2)m(25) so at bottom (1/2) m v^2 = that initial energy
December 7, 2016

Physics
LOL, you answered your own question Potential energy = m g h Kinetic energy = (1/2) m v^2 so (1/2) m v^2 = m g h = 73.8*9.81*23.9 Joules (your first answer) so v = sqrt (2 g h) (by the way, remember that. You need it frequently)
December 7, 2016

Math
4 1/3 = 13/3 cans/64 oz = 13 cans/192 oz so 96 oz (13 cans/192 oz) = 6.5 cans
December 7, 2016

Math
Sketch a number line mark them on it like from left to right -13 -7 0 +1 +7
December 7, 2016

Algebra 1
3 y = - 2 x + 12 so y = (-2/3) x + 4 m = -2/3 and b = 4
December 7, 2016

History
You are welcome.
December 7, 2016

History
Oh my ! First check Constitution Amendment 10. Powers not delegated to the US gov. by the Constitution are reserved to the states or to the people (look up exact wording). Local governments do not exist in the Constitution but States reserve powers for them. We are a UNION of ...
December 7, 2016

Math
You are welcome and good luck ! I hope your grandmother comes through all right.
December 7, 2016

Math
To check #1 You say B which is y=3x+6 if x = 6 y = 3(6) + 6 = 18+6 = 24 NO! See, you can check without asking me. y = 18+b y = 8 8 = 18+b b = -10 so the RIGHT answer is y = 3x -10 which is A now slope of first = -3 second is 6y = 2x + 3 , slope = +1/3 second slope = -1/first ...
December 7, 2016

Math
9-t
December 7, 2016

Math
6*37+43 if she always works 37 hours per week income = 6 * 37 + tip otherwise income = 6 * hours + tip
December 7, 2016

Physics
second problem same Newton One stuff.
December 7, 2016

Physics
x momentum = 61.2 * 2.25 FOREVER y momentum = 66.2 * 1.30 FOREVER so final mass = 61.2+66.2 = 127.4 final x momentum : 127.4 * Vx = 61.2*2.25 Remember? final y momentum 127.4 * Vy = 66.2* 1.30 final speed = sqrt(Vx^2+Vy^2) tan theta = Vy/Vx where theta is angle above +x axis
December 7, 2016

Algebra 2 Honors
You are welcome.
December 7, 2016

oh my
My work - 2 = 1/4 ?(100 - h) I multiplied both sides by 4 from - 8 = ?(100 - h) ------------- OK SO FAR BUT square both sides 64 = 100 - h h = 100-64 h = 36 domain from 100-h must be + 0<h<100 for range if h = 0, t = 10/4 hits ground if h = 100, t = 0 drop it then so 0&...
December 7, 2016

Thank you Philip
Thanks :)
December 7, 2016

Physics
3.4 WHAT?? I assume radians/second but hard to say. I will use that but if RPS or something, convert I disk = (1/2)m r^2 so Id = .5*.4*.36^2 and It = .5 * 1.7 * .36^2 initial angular momentum = It*3.4 final angular momentum (the same of course) = It omega +Id omega = omega(It+...
December 7, 2016

Math
13 people ( 2 pounds/5 people) = 26/5 = 5.2 pounds
December 7, 2016

Chem
http://www.google.com/search?q=positron+decay&ie=utf-8&oe=utf-8
December 7, 2016

math
You already have the answer minimum cost is at the vertex x = 20 cars and C = 700 dollars this is a parabola, its vertex is at the bottom,
December 7, 2016

Math
constant slope, straight line y = m x + b m is constant rate of change of y with x
December 7, 2016

math algebra
3.2 = .01 h^2 + .2 h + 1.2 .01 h^2 + .2 h - 2 = 0 h^2 + 20 h - 200 = 0 h = -10+/- 10sqrt3 h = 7.32 hr ===================== check h = about 7.3 .01 h^2 = .53 .2 h = .15 + 1.2 = 3.2 ok, it works
December 7, 2016

Statistics
Combinations p = .65 1-p = .35 P(7,10) = C(7,10) .65^7 * .35^3 C(7,10) = 10!/[7!*3!] =10*9*8/[3*2] = 5*3*8 = 120 so 120 * .65^7 * .35^3 = .252
December 7, 2016

Physics
there are 3600 seconds in an hour 2000 hr (3600 s/hr) = 7,200,000 seconds
December 7, 2016

math
You are welcome.
December 7, 2016

math
where is the vertex of that parabola? You do not say if you know calculus so I will assume we do it the hard way with algebra .009 x^2 -1.08 x = -h -.4 x^2 - 120 x = -111h - 44.4 x^2 -120 x + 3600 = -111h + 3556 (x-36)^2 = -111(h-32) vertex at x = 36 and h = 32 32 -26.5 = 5.5
December 7, 2016

Physics
friction force = 10*9.81*.42 = 41.2N net force = 200 - 41.2 = 158.8 N a = 158.8 / 10 = 15.9 m/s^2
December 7, 2016

produces?
if you put 150 in and get 40 out it is 100(4/15) = 27% but it has to get energy from somewhere. It can not "produce" 150 + 40 +110 without putting any energy in. I suspect a typo in the problem description. It does not produce 150 J, it absorbs 150 J
December 7, 2016

physics
sin 24 = h/3 v = sqrt (2 g h) Now this is virtually the same as your roller coaster problem. Study conservation of energy and potential energy in gravity field.(mgh) and kinetic energy (.5 m v^2)
December 7, 2016

Chemistry
perhaps this can help: http://physics.stackexchange.com/questions/7993/photon-hitting-an-atom-with-higher-energy-than-needed-to-ionize Also maybe Google: Einstein photoelectric effect
December 7, 2016

Physics
check, drops 15 meters to top of loop v^2 = 2 g (15) needs v^2/30 = g sure enough 2*15 g /30 = g
December 7, 2016

Physics
Note this does no depend on the mass (lucky or it would be different for skinny kids and fat adults), or even on g (independent of planet:)
December 7, 2016

Physics
g = v^2/r at top of loop g = v^2/30 solve for v^2 = 30 *g now the car drops A-2r to that point at the top of the loop (1/2) m v^2 = m g (A-60) v^2 = 2 g(A-60) 30 g = 2g (A-60 ) = 2 g A -120 g 150 g = 2gA A = 75 check my arithmetic !
December 7, 2016

Trignometry
He told you how to do it 1. add the south components of each to get the south component of the resultant , S 2. add the west components of each to get the west component of resultant, W get the magnitude sqrt(S^2+W^2) tan A =W/S where A is angle west of south
December 7, 2016

wrong
(4*4)/(4*6) = 4/6 = 2/3
December 7, 2016

Math
x _y____y(n)-y(n-1) ___ next diff 1__0______ 2__5______ 5 3__10_____ 5____________0 4__15_____ 5____________0 5__20_____ 5____________0 6__25______5____________0 THAT is constant diff now x _y____y(n)-y(n-1) ___ next diff 1__1______ 2__4______ 3 3__9_______5____________ 2 ...
December 7, 2016

Physics
1 what? coulombs/m^2? coulombs/cm^2 ? I will assume m^2 and call it x area = A = 4 pi r^2 A = 4 pi (r)^2 Q = 1* A potential= V = k Q/r = Q/(4 pi eo r) V = 1* 4 pi r^2/(4 pi eo r) V = r/eo
December 7, 2016

Physics
mass(specific heat * 40 + heat of fusion of water)
December 7, 2016

Physics
.25 * heat of vaporization of water
December 7, 2016

no
there is no temp change involved here, just the heat to melt at 0 Q = mass * heat of fusion = 3 * 3.3*10^5 = 9.9 * 10^5 Joules
December 7, 2016

Maths
(2/3)(600) = 2(200) = 400
December 7, 2016

Algebra
.7 x + .2 y = .4*500 x + y = 500
December 7, 2016

Physics
a = -9.81 =-g v = -9.8 t h =Hi - Vit - 4.9 t^2 = Hi -4.9 t^2 You do not say the original height, Hi Vi, initial speed, is 0 so t ____ a ___ v ___ h 0 ___ -g ___ 0 ___ Hi - 0 1 ___ -g ___-9.8__ Hi - 4.9 2____ -g____-19.6_ Hi - 19.6 3 ___ -g ___-29.4_ Hi - 44.1
December 7, 2016

physics
force in direction of motion * distance moved = 300*10 = 3,000 Joules
December 7, 2016

science
I am inclined to agree with you, thinking about India moving north.
December 7, 2016

Physics
fell 40 m v then is Vi =sqrt(2gh)= sqrt(2*9.81*40) = 28 m/s so in the 12 m he slows from 28 to 8 m/s average speed = (28+8)/2 =36/2 = 18m/s t = 12 / 18 = 2/3 second average total force = change in momentum/time = 55 * 20 *3/2 = 550*3 = 1650 but add the weight which the bunge ...
December 6, 2016

Physics
there are 60*60 = 3600 seconds/hr 2000 hr *3600 s/hr = 72*10^5 s times 100 watts = 72*10^7 Joules 720 million Joules :)
December 6, 2016

You mean zeros of f(x)?
x = [5 +/- sqrt(25 -12) ]/2 = [5 +/- sqrt (13) ]/2 now run your calculator
December 6, 2016

Math liberal arts 2
yes
December 6, 2016

Math
You are welcome.
December 6, 2016

Math
yes it is, it goes up 8 and right 3 graph it :)
December 6, 2016

Math
dy/dx = (13-5) / (4-1) = 8/3
December 6, 2016

Algebra
6 -2+4i needs -2-4i that is three, we need two more but your last one is real, therefore I suspect a typo perhaps it should be 4 - sqrt-2 which is 4 -i sqrt 2 then we would have 4 - i sqrt2 and 4 + i sqrt 2
December 6, 2016

Math
multiply everything by A m t mt = At + Am At = m (t-A) t = m(t-A)/A
December 6, 2016

Math
m = minivans p = other (what we want p = (5/2) m or m = 2 p/5 m + p = 39 2 p/5 + 5 p/5 = 39 7 p/5 = 39 well, you are not going to get a whole number of vehicles
December 6, 2016

Chem
2 electrons fit it that first shell. Helium has exactly 2, no extras and not short any. Therefore He does not want to combine with other atoms, including another He to form a chemical compound or molecule. Therefore called "noble". Hydrogen for example has ONE ...
December 6, 2016

math
with what you wrote we can combine like terms, but with no equation we can not calculate a value for a
December 6, 2016

math
2 a + 2
December 6, 2016

Probability Help
1/10 *1/10 * 1/10 * 1/10 = 1/10,000
December 6, 2016

College Math
4 w and 5 b so 9 first one 5/9 second 4/8 third 3/7 fourth 2/6 so 5/9 * 1/2 * 3/7 * 1/3 (5)/(7*18) = 5/126
December 6, 2016

Math
base^logbase (x) = x w^ log Subscript w (Q)=w^ 13 Q = w^13
December 6, 2016

Math
dr/dt = .118 r dr/r = .118 dt ln r = .118 t + c r = e^(.118 t +c) = e^c * e^.118t when t = 0, e^.118t = 1 r = e^c = 300 so r = 300 e^.118 t
December 6, 2016

Algebra
7y = -4 x + 8 y = -(4/7) x + /7 so m = -4/7 y = -(4/7)x + b -2 = -(4/7)(4) + b -14/7 + 16/7 = b b = 2/7 so y = -(4/7)x + 2/7 7y = -4x + 2 for the second one m = -(-7/4) = 7/4 so y = (7/4) x + b now put x = 4 and y = 2 in again to find b
December 6, 2016

Algebra I doubt it
570 feet/second ???? You threw it up at about 400 miles per hour, typo but anyway where is the vertex of that parabola? 16 t^2 -570 t = -h t^2 - 265/8 t +265^2/16^2 = -h+265^2/16^2 (t-265/16)^2 = etc so vertex at t = 265/16 BUT I do not believe you
December 6, 2016

math
No one knows, you only talk about tons, not how many rods in a ton. We can do tons (1/8)(3/4) = 3/32 ton
December 6, 2016

Algebra
(810,000 - 520,000)/(2013 - 2000)
December 6, 2016

Calculus
what is f(8)? -6x^2 + 96x + 7 =-6(64) +96(8) + 7 = -6(64) +12(64) + 7 = 6(64) + 7 = 391 now you say f(10) is bigger? -6(100) +96(10) + 7 -600+960+7 367, nope , disagree
December 6, 2016

Calculus
this is a parabola since we have a negative coef of x^2 it opens down (sheds water) the real question is, where is the vertex? complete the square 6 x^2 -96 x = 7 x^2 - 16 x = 7/16 x^2 -16 x + 64 = 64 7/16 (x-8)^2 vertex at x = 8 Yes, you are right , e.
December 6, 2016

Math
You are welcome.
December 6, 2016

Math
204/4 = 51 408/8 = 51 510/10 = 51 miles per hour 51mi/1hr so A.
December 6, 2016

Math
D =f(t)
December 6, 2016

ARCHIMEDES PRINCIPLE
http://mathworld.wolfram.com/CircularSegment.html
December 6, 2016

geography
well, in Gloucester MA we are about 70 west of Greenwich England so go a bit further west, like Chicago is about 87 W, St Louis MO is 90 ! then look north or south of there Look at a map or globe or maritime/air chart
December 6, 2016

Science
LOL, it was about the horizontal plane, but yes that could happen
December 6, 2016

How to upset me
That did it !
December 6, 2016

Science
NEWTON'S FIRST LAW !!!!!!!!!!! There is NO external force on this system therefore There is NO CHANGE of momentum. Never ever forget that !!! D. !!!!!!
December 6, 2016

Physics!!!!!!
force * time = change in momentum 360 * t = .18*26 solve for t a = change in velocity/time = -26/t Vi = 26 d = Vi t + (1/2)a t^2 d = 26 t - (1/2)(26)t d = 13 t
December 6, 2016

The Simplex Method
therefore at the intersection of 5x+10y?560 and 50x+20y?1600
December 6, 2016

The Simplex Method
http://www.wolframalpha.com/widget/widgetPopup.jsp?p=v&id=1e692c6f72587b2cbd3e7be018fd8960&title=Linear%20Programming%20Calculator&theme=blue ========================== 3220 at (12,50) ========================== maximize | function | 60 x + 50 y\ndomain | x + y<=80 && 5 x...
December 6, 2016

calculus
3 of length x 1 of length y A = x y length of fencing = 3x+y = 600 so y = (600 - 3x) A = x(600 - 3x) = -3 x^2 + 600 x dA/dx = -6 x + 600 min or max A when 6 x = 600 or x = 100 then y = 300 A = x y = 30,000 ft^2 or about 3/4 of an acre
December 6, 2016

Describing Data
you mean the mean frequency I suppose? add them up and divide by 4
December 6, 2016

Algebra 2
use first choice, area from values mean 450 sd 50 between 400 and 500 output is .6827 or 68% are between well that is a little less thsan .7*160 = 112 so 109
December 6, 2016

Algebra 2
http://davidmlane.com/hyperstat/z_table.html
December 6, 2016

physics
I assume in series E = i R + L di/dt let i = a (1- e^-kt) then di/dt = a*k e^-kt when t =oo , E=i R i = E/R = a so a = E/R so i = (E/R)(1-e^-kt) di/dt = (E/R) k e^-kt when t-->0, i = 0 and di/dt = a k so E = L di/dt = L a k = L(E/R)k so k = R/L so In the end all that we ...
December 6, 2016

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