# Posts by Damon

Total # Posts: 31,029

**math**

(4/3) pi r^3 = .5236 = 0.5 in^3

**Calculus**

at b = x^3 the change of the integral with x = y'(x) [ it is the value of the function at that limit ] =10 x^3/2 sin( x^3 )

**physics**

remember wavelength = speed of sound * T = speed of sound / f and then http://www.physicsclassroom.com/class/sound/Lesson-5/Open-End-Air-Columns

**physics**

http://hyperphysics.phy-astr.gsu.edu/hbase/Sound/souspe.html frequency closed end pipe

**physics homework**

impulse = change of momentum all vertical, no change in horizontal speed from -v cos 60 to + v cos 60 2 m v cos 60

**physics**

initial momentum north = 55*1.1-7*1.8 Now I assume she picks the dog up and the system moves on with the same momentum final momentum north = (55+7)v so 62 v = 55*1.1 - 7*1.8

**physics**

well, the initial momentum was zero so the final momentum must be zero. I assume the first cart goes back and the mouse and cart two go forward so 0 = -.35*.8 +(.054+.25)V2 .28 = .304 V2

**Physics**

0 = Hi - Vi t - 4.9 t^2 0 = Hi - 0 (t+4) - 4.9 (t+4)^2 0 = Hi - 40 t - 4.9 t^2 ------------------------------ Hi = 4.9 t^2 + 40 t Hi = 4.9(t^2+8t+16) --------------------- 4.9 t^2+40 t = 4.9 t^2+39.2t +78.4 .8t = 78.4 t = 98 Hi = 40t+4.9t^2 =40*98+4.9(98^2) =50,980 meters (30 ...

**Physics**

Heat of fusion of water (water to ice transition) is 3,340,000 Joules/kilogram so 2.4 * 3,340,000 Joules The mixture stays at 0 degrees centigrade until the ice is all melted. That is how ice works in your cold drink.

**math**

1.07 * 10^4 = 1.0700 *10^4 so I can count four to the right = 10,700

**Algebra 2**

You are welcome.

**Algebra 2**

Yes like (x-h)^2= 4(a(y-k) is a parabola (x-h)^2/a^2 + (y-k)^2/b^2 = 1 is an ellipse if a^2=b^2 then circle of radius a^2=b^2=r^2 if - sign between, then ellipse turns to hyperbola etc

**Calculus**

one way x = + y^1/2 , double answer for the negative x part 2 int[ x 2 pi (7-y)dy] from y=1 to 7 4 pi int y^.5(7-y)dy 28 pi int y^.5 dy - 4 pi int y^1.5 dy 28 pi {y^1.5/1.5} - 4 pi y^2.5/2.5 at 7 (28/1.5)pi 7^1.5 -(4/2.5)pi 7^2.5 at 1 (28/1.5)pi -(4/2.5)pi subtract at 1 from at 7

**19? typo?**

This question does not make any sense. The mass does not change when it is lifted by Archimedes. the mass is 19 * 1 gram/cm^3 * 20 cm*3 = 380 grams

**math**

That is a horizontal line, changeless forever and ever, no slope at all :)

**physics**

each would create a E vector pointing through the center from the charge segment. The components perpendicular to the diameter add. The components parallel to the diameter cancel each other. So you end up with an E vector perpendicular to that diameter. If you do the other ...

**physics**

3/2 the length same charge so 2/3 the density (3/2) * 10 = 30/2 = 15 so increase by 5 nC

**Statistics**

check AREA box put in Area = .05 result is 95 % are below 698

**Statistics**

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

**Math**

any element in one must be in the other. any element not in one cannot be in the other :)

**Math**

Draw Venn diagram

**Pre-Algebra**

change in y/change in x = (-5-10) / (1+4) = -3 or = (-20+5) / (6-1) = -3 or = (-20 -10) / (6+4) = -3 remarkable, the slope is constant and is -3 so y = -3 x + b now put any of those points in 10 = -3(-4) + b b = -2 so y = -3 x - 2 NOW check that with another point like -20 = -...

**physics**

well let's call the specific heat of water = k. It does not matter what it is now the heat added to the cold = the heat taken from the hot 2000 k (20-5) = m k (70-20) 2000 (15) = m (50) m = 2000 (15/50) grams

**Pre-Algebra**

Base Area * height for CYLINDER pi r^2 h = pi * 16 * 3 = 48 pi BUT for CONE anything pointy with straight sides (1/3) * Base area * height = 48 pi/3 = 16 pi

**math**

(6/7)(7/8)(70) = .75*70

**8th grade math asp help**

top = pi r^2 sides = 2 pi r h pi (64 + 16*12) pi (64 + 192) 256 pi = about 804

**Pre calc**

oh, cos also - in quadrant 3 cos a = -9/11

**Pre calc**

but she said pi/4 :)

**Pre calc**

well, the sides could be 1, (2/9)sqrt10 and hypotenuse 11/9 or 9, 2 sqrt 10, 11 with 2 sqrt 10 opposite ? we know sin ? <0 so ? in quadrant 3 or 4 since tan is +, must be quadrant 3 now actually cos(a-b)=cosa cosb + sina sinb cos a = 9/11 cos b = 1/sqrt 2 sin a = -(2/11) ...

**physics**

if x = a sin wt v = aw cos wt a = -w^2 x when x = 0 |v| is MAX so Ke is MAX total energy is CONSTANT So only acceleration which is proportional to x

**Math gibberish**

Please proof read.

**Trig**

[sin/cos] / [ 1 - sin^2/cos^2 ] sin cos / [cos^2-sin^2] sqrt3/4 / [ 3/4 - 1/4 ] (1/2) sqrt 3

**math**

6/8 = 3/4 3/4 * 28 = 21

**laplace transformation:help damon or steve or rein**

arrggh, you will have to type them in as d^3y/dt^3 -3 d^2y/dt^2-3dy/dt and t^2 e^t

**laplace transformation:help damon or steve or rein**

left http://www.wolframalpha.com/widget/widgetPopup.jsp?p=v&id=122507de3372c73f916a1d07ccb9cf9c&title=Laplace+Transform+Calculator&theme=blue&i0=cos right http://www.wolframalpha.com/widget/widgetPopup.jsp?p=v&id=122507de3372c73f916a1d07ccb9cf9c&title=Laplace+Transform+...

**physics**

reduce distance by half, multiply the force by 2^2 = 4 k Q1 Q2 / d^2

**maths steve reiny bob reiny!!! Help**

y = -2x -3 the slope = -2 y = (1/2)x - 1/2 slope = 1/2 so perpendicular, whew that helps. where do they cross? That is a corner. (x-1)/2 = -2x-3 x-1 = -4x -6 5x = -5 x=-1 y = 2-3 = -1 so other corner is (-1, -1) now draw it and find the other two intersetions

**Calculus**

dy/y = dx/x^2 ln y = -1/x + c y = C e^-1/x http://www.wolframalpha.com/input/?i=Solve++y%27(x)+%3Dy%2Fx%5E2

**Calculus**

http://www.wolframalpha.com/input/?i=Solve++y%27(x)+%3D+x%2Bxy

**math- integral**

what you are really asking is how fast is the area changing at t = x which is the value of the function itself at t = x x^5 sin(-7x-4)

**Calculus**

the value of the function at t = x^2 = (x^2)^x^2

**Please check carefully for typos**

stiffness must be force/distance, for example Newtons/meter. kg is mass, not force and I have no idea what s2 means. similarly b *dx/dt would be a force in Newtons where b would have units Newtons seconds/ meters

**Physics (Attempt 3 for help)**

Yes, it does look familiar :)

**physics**

F = k q1 q2 /d^2 q1*q2 = 6*2 = 12 new q1*q2 = 8*4 = 32 so (32/12)12N = 32 N

**Geometry**

d = length w = width center at 1/2 d and at 1/2 w (1/2)d - (1/2)w = 4 d+w = 56/2 = 28 so w = 28-d d - (28-d) = 8 2 d = 36 d = 18 then w = 10

**physics**

To do positive work, you must push in the direction of motion. That requires an increase of volume as the walls of the balloon move out :) It could be that the internal energy decreases at the same time but you might be putting heat in.

**physics**

10 grams * 2 J/gdegK = 20 J/degK 20J/degK * 10 deg K = 200 Joules to get it all to the boiling point then boil 5 grams with remaining 200 J heat/gram = 200 Joules/5 grams = 40 Joules/gram

**maths**

1.85 = (1+r)^5 log 1.85 = 5 log(1+r) use any base logs, base 10 or ln or whatever

**Physics**

assuming kilograms (please specify units) water is 4180 J/(kg deg C) heat into water = (0.1)4180*(32-20) Al is C J/(kg deg C) heat out od Al = .004(C)(100-32) so .004(C)(100-32)=(0.1)4180*(32-20)

**What do you think?**

I am not about to just answer this for you. Read about the difference between the economies of the North and the South.

**Math**

new length = 100 + 2 x new width = 50 + 2 x new area =(2x+100)(2x+50) so (2x+100)(2x+50) - 50*100 = 459 solve quadratic :)

**Chemistry**

Na = 23 g/mol Cl = 35.5 g/mol so NaCl = 58.5 g/mol so n = 42/58.5

**Chemistry**

heat generated = spec heat of water (202 grams)(27.33 - 25.00) divide by 1000 if that is in Joules to get kJoules divide by 2 grams to get kJ/gram

**Chemistry**

the gage pressure (pressure above one atm) would be (5/3)*1 atm but 1 atm = 101325 Pascals=101.325kPa so (5/3)(101) kPA if you want absolute pressure add 1 atm or 101 kPa to that

**Chemistry**

let C = specific heat of water heat gained = C*30*(T-280) heat lost = C * 50(330-T) so 30(T-280) = 50 (330-T)

**physics**

photon energy = h * frequency h = 6.626*10^-34 Joule seconds * 5.14*10^14 cycles/second

**Proof by contradiction**

Yes, however you do it, the vertex is above the x axis :)

**Proof by contradiction**

4x^2+1/4x <1 Can I simplify this inequality in the following way: multiply both sides by 4x so we have. 4x^2+1 <4x+1 ========================== I have no idea what you have and what you are doing. First of all, whatever, No If you have (4x^2+1)/4x <1 NOTE-parentheses ...

**Deduction**

deduction is incorrect draw Venn diagram we only know that the rainstorm is in the umbrella circle. He could easily carry the umbrella in a dry northwest breeze. hypothesis: If a cow, then a mammal Converse: If a mammal, then a cow (false) Inverse: If not a cow, then not a ...

**Physics**

Say the river runs south We want to end up going east Our velocity north will be 6 cos T - 3 = 0 if T is angle from north cos T = 1/2 T = 60 degrees from north which is 30 degrees from straight across

**Math**

| x - -2| = 3 is |x+2| = 3 try x = 1 try x = -5 :)

**calculus**

if y"'= -6 then y" = -6 x + c when x = 0, y"=2 = c so y" = -6x + 2 y' = -3 x^2 + 2 x + d y = -x^3 + x^2 + d x + e 1 = -1 + 1 + d + e 7 = -8 + 4 +2d + e so 1 d + e = 1 2 d + e = 11 ------------------ -d = -10 d = 10 so e = -9 and y = -x^3 + x^2 + 10 ...

**science (please please please help)**

I am no biologist but suspect you are right. Obviously the plant benefits from the N2 but I do not think the bacteria would be there unless they gained something (like a home). The other choices make no sense.

**Pre-Calc Trig**

well, where is the center of the wheel above ground? 12 + 67/2 = 45.5 = center above ground It does not say where the wheel starts so I will say it is at height = bottom now in general h = 45.5 + 33.5 sin( 2 pi t/T -p) where T is period in seconds and p is phase in radians Now...

**Math**

15*4*6 = 360

**HURRY MATH!**

$350/35hr = 10 dollars/hr -- correct

**Physics incomplete**

You have to know how far it is submerged m = 0.360 kg g = 9.81 m/s^2 tension = m g - buoyant force buoyant force = submersed volume * 900 kg/m^3 * g

**Math**

sides are x x-5 x-7 so 3x-12 = 42 3x = 54 x = 16 etc

**width typo**

I do not understand the width 1/1

**AP Physics**

positive is force up on feet 691 up - m g down = 0 if motionless if g = 9.81, m = 70.44 kg F - m g = m a where a is up 499 - 691 = 70.44 a a = -2.73 so accelerating down (negative a)

**physics**

change in velocity divided by time. (45-25)/10

**Math 8**

Two parallel lines never cross, no solution. y = 2 x - 4 y = 2 x + 4

**Social Studies**

Agree, if you lose 20 people in one fire they are probably crowded into tiny spaces.

**physics**

m g h = 6 * 9.81 * 12 Joules

**Math**

commission per CD = .08*12 = .96 so 52.8/.96

**Calculus**

(1/2)x^2+2x at 4 - at 1 = 8+8 - 1/2 -2 = 13.5 assuming by under you mean below the line and above the x axis

**Math**

(b-7)(s-7) = 72 b = s+6 so (s+6-7)(s-7) = 72 (s-1)(s-7) = 72 s^2 - 8 s + 7 = 72 s^2 - 8 s - 65 = 0 (s-13)(s+5) = 0 s = 13 then b = 19

**physics**

500 = m (heat of fusion + specific heat of water*4 deg)

**AP physics (simple experiment question)**

yes, you have the idea. The points on the bar that do not move are the nodes. The sand flies off the rest of the bar.

**AP physics (simple experiment question)**

google beat frequency eg http://hyperphysics.phy-astr.gsu.edu/hbase/Sound/beat.html google nodes normal modes eg http://en.wikipedia.org/wiki/Normal_mode

**Math- Ms. Sue? Steve? Writeacher?**

(4,2) is in the first quadrant (5, -3) is in fourth quadrant, lower right across y axis, same y, change sign of x (-5,-3) quadrant III

**Physics**

time = 1/frequency = 1/(2.7*10^9) =(1/2.7)* 10^-9 seconds distance = speed*time = 3*10^8 *(1/2.7)(10^-9) = about 0.1 meter = 10 cm

**Maths**

You need as many equations as unknowns. Here yoou have 3 unknowns and two equations so no unique solution. There are two basic ways: 1, substitution, for example say s = 100 - (c+h) and use that for ss in the next equation so 40[ 100-(c+h) ] +65 c + 2 h = 3279 now you do not ...

**Proof by contradiction**

what happens if x > 0 ? what happens if x < 0 ? what happens if x = 0 ?

**physics**

average speed across window = 1.3/.22 = 5.91 m/s speed at top of window = Vt speed at bottom of window = Vb in general v = Vi + g t = Vi + 9.81 t so Vb = Vt + .22*9.81 = Vt + 2.16 Vt+Vb = 2 Vt + 2.16 (1/2)(Vt+Vb) = Vt + 1.08 = 5.91 so Vt = 4.83 m/s how far did it drop from a ...

**physics**

mass times acceleration. Your units are correct and your answer will be in Newtons of force. However m/s^2 not m/s2. The convention online is to write exponents as ^

**Math**

y = x^3

**social studies**

Agree first two. I think you are right about Paraguay as well, 1811.

**Math**

y = amount at end of every week after 4 weeks = 1700 + 200 (x-4) so y - 1700 = 200(x-4)

**Math**

draw triangle 40 + 50 + p = 180 p = 180 - 90 p = 90

**world history**

First you decide, then perhaps someone will review your answer. What do you think and why?

**Precal**

Now this is just like the other one (cos x/sin x)^2 - (1/sin x)^2 = (cos^2 x - 1)/sin^2x = sin^2 x / sin^2x = 1

**Calculus**

This is an odd function so its integral from -1 to +1 will be zero but anyway find average value on that interval that is the integral /(1 - -1)= integral/2 integral = (1/4)x^4 - 8x^2 from -1 to + 1 = 1/4-8 -(1/4)+8 = 0 so where is the function zero? at x = 0 of course I think...

**Physics**

I already did this http://www.jiskha.com/display.cgi?id=1491155418

**algebra 1**

the van uses 1 gal/20 mi so amount used = x/20 the tank holds V gallons so amount remaining after x miles y = V - x/20 we are given a point on that line 10 = V - 120/20 V = 10 + 6 = 16 gallons so in the end y = 16 - x/20

**Maths**

I am going to guess that your mean: 1/(1-x) + 2/(1+x) multiply tops and bottoms by [(1-x)(1+x)] [(1+x) + 2(1-x) ] /(1-x^2) **** remember a^2-b^2 =(a-b)(a+b) *** = [3 - x]/(1-x^2)

**Physics-Graivty**

F = G m M/r^2 F' = G m 2M/(2r)^2 F'/F = 2/4 =1/2 700* 1/2 = 350 N

**Physics**

100 = V i so i = 100watts/110 volts=about 1 coulomb/second (you use calculator) e = 1.6*10^-19 coulomb so (1/1.6)*10^19 electrons/second so 800 hours = 800*3600 seconds = 8*3.6*10^5 seconds so (8*3.6/1.6)* 10^24 electrons (quite a few)

**11 grade / physics**

5 kg*40cm = m kg *30 cm m = 5(4/3) = 20/3 kg

**Trig**

volumes of similar objects have dimensions proportional to length dimension cubed 800/2700 = 8/27 = 2^3/3^3 = (2/3)^3 so (2/3)15= 10 inches radius