Thursday

December 8, 2016
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*