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March 27, 2017

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Posts by Damon

Total # Posts: 29,627

physic
up for time t then down for time t (parabola) u = 100 cos 45 forever Vi = 100 sin 45 at start v = Vi - g t at top v = 0 so at top t = Vi/g = 100 sin 45 / 9.81 in the air for time = 2 t so range = 2 t u = 2 t (100 cos 45)
January 14, 2017

Calc
f = ln g df/dx = df/dg * dg/dx we were given dg/dx what is df/dg ? df/dg = d ln g / dg = 1/g so df/dx = (1/g)tan 2/(1+x^2) I think you mean = (1/5)tan 2/2 = (1/4) tan one radian or 180/pi deg = (1/5)(1.055741 ) = .31148 so agree
January 14, 2017

physics
do horizontal and vertical separately I assume j is up v = 13 - 9.81 t y = 0 + 13 t -4.9 t^2 If y is negative, it dug a hole :) and x = 12 t so d = 12 t i + (13t-4.9t^2) j
January 13, 2017

math
we have 9 * 300 = 2700 bee months of honey we now have 450 bees 2700 bee months / 450 bees = 6 months
January 13, 2017

physics
The trick here is guessing the drag coefficient of the raindrop shape. See: http://home2.fvcc.edu/~dhicketh/DiffEqns/Spring11projects/Ben_Lynch_Gavin_Lommatsch/DiffEqProject/DiffEqProjectGavinBen.pdf It is a function of Reynolds number even if the shape is spherical. However ...
January 13, 2017

mathematics
original, then difference, then difference of difference 2 ...... 3 5 ........... 2 .......5 10 .......... 2 .......7 17 ...........2 .......9 26 constant difference of differences is parabola well, y = x^2 + 1 works an = n^2+1
January 13, 2017

What?
Check for typos please. If you mean merged, same total volume, then with the same height, the base areas add up to the original. pi R^2 = pi r1^2 + pi r2^2 R2 = sqrt( r1^2 + r2^2)
January 13, 2017

maths
of course the area of ABC = (1/2)(3*4) = 6 :) also (1/2)(AD)(5) = 6 AD = 12/5 = 2.4 cm
January 13, 2017

The cay is the book
C is the only choice that indicates determination.
January 13, 2017

Physics
how long does it take to get from 100 to 30? v = vi + a t 30 = 100 - 4 t 4 t = 70 t = 17.5 s how far did we go? average speed = 130/2 = 65 65*17.5 = 1137.5 ft how far did the freight go? 30 * 17.5 = 525 525 + 600 = 1125 ft CRASH for part b x1 = 100 t - 2 t^2 x2 = 600 + 30 t ...
January 13, 2017

math
No, slant height is hypotenuse of triangle where altitude is one leg and half the base is the other.
January 12, 2017

Computing
n = 1 10 output = n*n print output n = n+1 if n = 6 quit otherwise go back up to 10
January 12, 2017

maths
3.14159.... is between 3 and 4
January 12, 2017

physics
I guess he is JUST prevented from slipping normal force = m g cos 43 force down slope = m g sin 43 so m g sin 43 = 520
January 11, 2017

physics
The same. If there is no acceleration there is no change in force (ignoring friction).
January 11, 2017

Direction?
Forces are vectors. If they are equal in magnitude but opposite in direction, they add to zero. If both in the same direction, then twice. If in between, then in between.
January 11, 2017

physics
Find the resultant of the two perpendicular forces |F| = sqrt (76.5^2+46.3^2) tan A = 76.5/46.3 where A is angle north of west our force is equal and opposite same |F| same angle but south of east
January 11, 2017

math
c = 3(c+3) -3(c-3) c = 3 c + 9 - 3 c + 9 c = 18
January 10, 2017

pure physics
Weight of water displaced = .25-.20 = .05 N which is the force up on the stone from the water.
January 10, 2017

error
2 a - 62 = 12 2 a = 74 !!!!! a = 37 b = 25 same answer anyway
January 9, 2017

Algebra
a+b = 62 so b = (62-a) a - b = 12 a -(62-a) = 12 2 a - 62 = 12 2 a = 50 a = 25 b = 62-25 = 37
January 9, 2017

Math
24/2.5 = 9.6 so 9 strips with a little left over but not really because some is lost in the kerf (the width of the blade)
January 9, 2017

Math, Physics
F = m g g = gsurface * Rearth^2/R^2 = 9.81 * Rearth^2/(Rearth+401500)^2
January 9, 2017

Math
A = x*y 32 = x+2y x = 32-2y A = (32-2y)y = 32y-2y^2 or y^2-16y = -A/2 you did not say if you are in algebra or calculus so I will do it the algebra way by completing the square y^2 -16y + (16/2)^2 = -A/2 + 64 (y-8)^2 = -(1/2)(A-128) y = 8 x = 16 and the area is 128 ft^2
January 9, 2017

please show your attempts
We are teachers. We do not do tessts for people.
January 9, 2017

physics
+250 :) weight = m g = 55*9.8 = 539 Newtons That is the normal force on the floor Max friction = .56*539 = 302 N
January 8, 2017

physics
weight = w = m g normal force = m g cos theta ratio = cos theta so cos 17 and cos 30
January 8, 2017

calculus
Oh, intercepts y = x^3-6x^2 0 = x^2 (x-6) bounced off x axis at x = 0 crossed x axis at x = 6
January 8, 2017

calculus
slope = 3 x^2 -12 x =3 x (x-4) second derivative (curvature) = 6 x - 12 so the slope is 0 at x = 0 and at x = 4 at x = 0 is that a min or a max or in inflection point? second derivative = -12 That is a maximum, starts down from there at x = 4 is that a min or a max or an ...
January 8, 2017

Chemistry
CuCO3 = 64+12+48 g/mol = 124 g 31/124 = .25 mol CO2 = 12+32 = 44 g/mol so 11 g for .25 mol for CuO, subtract:) 31-11 = 20 grams check: CuO = 64+16 = 80 g/mol .25*80 = 20 grams sure enough
January 8, 2017

calculus
two negative numbers can not add to +1
January 8, 2017

calculus
b.f(x)=x^3=x-4 Typo, makes no sense c. f(2)=8 f(-1)=-1 so 9/3 average slope =3 f' =3x^2 3 x^2 =3 x= sqrt(1) which is 1 !!!! but also -1 d f(4) = 2 f(0) = 0 so slope = 2/4 = 1/2 f' = (1/2)x^-1/2 = 1/2 x = 1 again
January 8, 2017

Math
a + b + c = 975 a - x = 12 b - x = 345 c - x = 126 --------------add a+b+c -3 x = 483 so 975 - 3 x = 483 3 x = 492 x = 164
January 8, 2017

physics
mapple Vapple +mweath*0 = (mapple+mearth) V V = Vapple (mapple)/(mapple+mearth) so yes mapple/(mapple+mearth) is not very big it might be kind of hard to measure :)
January 8, 2017

physics
The earth moves under your feet (but just a little).
January 8, 2017

Math
L(1-cosT) = 1/3 foot sin T = 4 feet/L so L sin T =4 1-cosT = 1/3L L sinT = 4 cosT = (3L-1)/3L so cos^2T = (9L^2 -6L+1)/9L^2 so 1-cos^2T = (6L-1)/9L^2 which is sin^2 T but sin^2T =16/L^2 so 16/L^2 = (6L-1)/9L^2 144 = 6L-1 6L = 145 L = 24.2 feet check my arithmetic!
January 8, 2017

calculus
dV = surface area * dr so dr/dt = dV/dt/(4 pi r^2) dr/dt = 2 /(4 pi *64)
January 8, 2017

math
well, you just said math, not calculus, which is why I completed the square to find the vertex of the parabola in the other problem. 3 4 5 triangle x = 4 y = 3 hypotenuse = 5 dy/dt = -2 ============================= x^2 + y^2 = 25 2 x dx/dt + 2 y dy/dt = 0 dx/dy = -(y/x)dy/dt...
January 8, 2017

math
r = x (1000-2x) r = 1000 x -2 x^2 2 x^2 -1000 x = -r x^2 - 500 x = -(1/2)r x^2 -500 x + 250^2 = -(1/2)r + 250^2 (x-250)^2 = -(1/2)(r-2(250)^2 ) x = 250 r = 2*250^2 = 125,000
January 8, 2017

Algebra
[ (x/3) -5 ] 7 = 28 (x/3) -5 = 4 x/3 = 9 x = 27
January 8, 2017

calculus
check end points f(-2) = -2+8 = 6 f(2) = 2-8 = -6 now find where derivative is zero f' = 1 -3x^2 = 0 when x = 1/sqrt3 or x = -1/sqrt3 if x = 1/sqrt 3 f = 1/sqrt3 -1/3sqrt3 =(2/3sqrt3) if x = -1/sqrt3 f = -1/sqrt3 +1/3sqrt 3 = -(2/3sqrt3) so the max and min are at the end ...
January 8, 2017

calculus
Well, try one of them. function is continuous and differentiable from 1 to 3 (note not at zero) f(3) = 3-1/3 = 8/3 f(1) = 0 [f(3)-f(1)]/(3-1) = 4/3 so where is the derivative 4/3? f'(x) = 1 + 1/x^2 where does 1+1/x^2 = 4/3 ? 1/x^2 = 1/3 x = sqrt 3 yes, that is between x = ...
January 8, 2017

Physics
pm=1.6gcm^-3 nonsense V = 40 cm^3 so mass = 20 + 40 * density of Hg which is not 1.6 g/cm^3
January 8, 2017

Math
original = p cents / pizza 10 p = total cost 9(p+60) = same total cost so 10 p = 9(p+60) p =540 cents = 5.40 per pizza so $54
January 7, 2017

math
n = original 1.2 n = before 300 .2 * 1.2 n = 300 so 1.2 n = 1500 n = 1250 books originally ===================== check ===================== 1.2 * 1250 = 1500 +300 = 1800 1.2*1.2*1250 = 1800 sure enough
January 7, 2017

Algebra 1
x = [2p+/-sqrt(4p^2+32p^2) ]2 = [2 p + sqrt(36 p^2) ]/2 = [2 p + 6 p ]/2 = 4 p
January 7, 2017

Math
(43/2)(3/4)= 129/8 left after tacos (2/3)(129/8) used for burgers times 4 for number of 1/4 lb burgers 4(2/3)(129/8) = 129/3 = 43 burgers
January 7, 2017

another subtraction error
360 - 12 = 348 348 = 23 t -23t/2 696 = 23 t t = 30.3 a = 23/30.3 = .759 m/s^2
January 7, 2017

Physics
freight train goes 6 t our train goes 6t+360 Vi = 29 Vf = 6 a assumed negative v = Vi - a t 6 = 29 - a t a t = 23 d = 6t+360 = 29t-(1/2)a t^2 360 = 23 t -(1/2)(23 t) 720 = 23 t t = 31.3 seconds to crash a = .74 whoops, forgot the .4 seconds to react we go 14.5 m he goes 2.4 m ...
January 7, 2017

Algebra 1
You are welcome.
January 7, 2017

Algebra 1
n + n+1 + n+2 + n+3 + n+4 = 5 n + 10 so (5n+10)/5 = 13 5n+10 = 65 5 n = 55 n = 11 so 11 , 12, 13 , 14, 15 old sum was 65 new sum is 53 difference is 12 so 12
January 7, 2017

Physics
Not really. I bet you have heard the word "Impulse" that is force * time which is change of momentum F = m a = m dv/dt so F dt = m dv = "impulse" but m dv is change in m v and m v is "momentum therefore F * time = change in momentum = impulse
January 7, 2017

Physics
change in momentum = force * time force up = 800 -55(9.81) = 260 N net up force so momentum = m Vi = 260*.25 = 65 so Vi = 65/55 = 1.18 m/s up (1/2)mVi^2 = m g h h = Vi^2/[2(9.81)] = .071 meters = 7.1 cm
January 7, 2017

algebra
x^2 - 3 x = 4 x^2 -3 x +(3/2)^2 = 4 + 9/4 (x-1.5)^2 = (1/4)(16 + 9) (x-1.5)^2 = (1/4)(25) = 25/4 x-3/2 = +/- 5/2 x = 3/2 +/- 5/2 x = 4 or x = -1
January 7, 2017

Algebra 2
You are welcome.
January 7, 2017

Algebra 2
w = x L = (x+1) H = (x-4) w L H = 84 so x(x+1)(x-4) = 84 but the easy way is to look at the answers listed 7 is one bigger than 6 4 is one bigger than 3 so it must be one of the last two if x = W = 6 L=7 H=6-4 = 2 that works if x =W= 4 L = 5 etc, does not work so 2,6,7 works (...
January 7, 2017

Physics
Fe 7.87 g/cm^3 Ag 10.5 g/cm^3 Viron* 7.87 + Vag*10.5 = 30 Viron + Vag = 20.4 ok?
January 7, 2017

Physicsthe weight on e
Our spring scales would not work on the moon correctly. We would have to multiply the measurement in grams or kilograms by 6 to get the right answer :) On the other hand a balance scale would work fine.
January 7, 2017

Physics
This is the second question in a row which confused mass and weight or force. Are you using the same old physics book I wonder?
January 7, 2017

Physics
well, 250*0.85 = 212.5 cm^3 so it displaces 212.5 grams of water assuming water has density of 1 gram/cm^3 If your book does force in grams, that is the answer. However that 212.5 grams is really the MASS of water displaced. To get the force up you really should multiply that ...
January 7, 2017

Physics
by the way, what we worked with here was mass, not weight. If this is a Physics course, your book should do mass in kg and weight in Newtons or mass in g and weight in dynes. weight = mass * acceleration of gravity. mass is the same on another planet, weight is different.
January 7, 2017

Physics
holds 40 g water that is volume = 40 cm^3 since density of water is about 1 g/cm^3 mass = 20 + 40*density of Hg density of Hg = 13.5 g/cm^3 so mass = 20 + 40*13.5 grams
January 7, 2017

Algebra 1
You are welcome.
January 7, 2017

Algebra 1
a = b + 2 c b = 2 c so a = 2 c + 2c = 4 c a + b + c = 77 4 c + 2 c + c = 77 7 c = 77 c = 11
January 7, 2017

math
you could do this by dividing the areas but that is not safe because it might not be exact one way or the other so 6 * 1.5 = 9 8 * 1.5 = 12 6*8 = 48 exactly
January 7, 2017

Math
4b+2p = 34 p = b-4 4 b + 2(b-4) = 34 4 b + 2 b - 8 = 34 6 b = 42 b = 7
January 7, 2017

algebra
3 z^2 = -108 z^2 = -36 z = +/-6 sqrt -1 = +/- 6i
January 7, 2017

algebra
5 x^2 = 651-536 = 115 x^2 = 23 x = +/- sqrt 23 = +/- 4.80
January 7, 2017

Math
49 - 2v
January 7, 2017

Math
three choices for the first digit 2 choices for the second 1 choice for the third 3*2*1 = 6 1 2 3 1 3 2 2 1 3 2 3 1 3 1 2 3 2 1
January 7, 2017

algebra
54 = 2*27 = 2*3*3*3 6 and 9 is 15 so (w-6)(w-9)
January 7, 2017

Calculus
5[xdy + ydx ] +x^2 dy+y(2x dx)=0 dy(5x +x^2) + dx(5y+2xy) = 0 dy/dx = =(5y+2xy)/(x^2+5x)
January 6, 2017

Chemistry
Ph determination
January 6, 2017

Chem 111
1000 kg/m^3 V = pi (d^2/4)h d = 6 ft = 1.83 m h = 17.5 ft = 5.33 m so V = [pi(1.83^2)/4 ]5.33 m^3 mass= 1000 * V in kg there are about 2.2 pounds/kg
January 6, 2017

Math
(2*27 + n)/3 = 29 54 + n = 87 n = 33
January 6, 2017

Need help with vector questions posted below
+1 1 3 -1 2 n +2 m 1 determinant = 0 2 + 2n -3m -12 -nm +1 = 0 2n-9 -m(3+n) = 0 m = (2n-9)/(3+n)
January 6, 2017

maths
everything in thousands two points on line (4,22) and (6,30) (30-22)/(6-4) = slope so slope = m = 4 c = 4 n + b 22 = 16 + b b = 6 so c = 4 n + 6 if n = 4.5 c = 4(4.5) + 6 c = 18+6 c = 24 so 24,000
January 6, 2017

Vectors - Maths [Second Question]
+1 -1 +2 +1 +2 -4 +m +6 -12 det = 0 -24 +12 +4m -4m +24 -12 = 0 I get any old m
January 5, 2017

Vectors - Maths
+1 1 3 -1 2 n +2 m 1 determinant = 0 2 + 2n -3m -12 -nm +1 = 0 2n-9 -m(3+n) = 0 m = (2n-9)/(3+n)
January 5, 2017

calculus
f(x+h) = 1/(2x+2h) f(x) = 1/2x f(x+h)-f(x) = (2x -2x-2h)/2x(2x+2h) = -2h/(4x^2+4xh) divide by h = -2/(4x^2+ 4xh) let h--->0 = -2/4x^2 = -1/2x^2
January 5, 2017

Calculus
Oh well h = 9 cm r = (6/12)9 = 4.5 cm dV = pi r^2 dh so dV/dt = pi r^2 dh/dt -3 cm^3/min = pi (4.5)^2 dh/dt so dh/dt = -3/[ pi(4.5)^2] about .047 cm/min
January 5, 2017

Calculus
No. The answer is in cm/min not cm^4/min. I did not check the arithmetic.
January 5, 2017

Calculus
I and also Steve have answered a million of these. For example: http://www.jiskha.com/display.cgi?id=1415757944
January 5, 2017

incomplete
earned how much in a year, call it x percent = 100 (x/9000)
January 5, 2017

Maths
By the way for small angles most of us assume sin theta = tan theta = angle in radians where angle in radians = angle in degrees * pi/180 then the arc length = chord length = R theta
January 5, 2017

Maths
LOL, If you really want to do it as an isoceles triangle with equal legs of length 5.06 e13 miles then sin .5 minutes = (x/2)/5.06e13 x = 5.06 e13 * 2 sin .5 min sin .5 min = sin (.5/60) degrees = .000145441 times 10.12 e13 = .00147186292 e13 = 1.47 e10 again:)
January 5, 2017

my typo
found error so your arc length in light years is 2 pi(8.611)/(60*360) = .0025048 light years which is 1.47e10 miles (those are land, not nautical miles) To get it go to Google and type .0025048 light years = miles and hit enter or use calculator and speed of light.
January 5, 2017

Maths
Clearly parallax is not a problem at this distance :)
January 5, 2017

Maths
You are right, I have an arithmetic error I estimate that 8.6 light years ia about 5.06 * 10^13 or 5.06e13 miles one minute is 1/21,600 of the circumference [ that is 1/(360*60) because 360 degree and 60 minutes per degree] circumference = 2 pi r = 2 pi * 5.06e13 = about 31 ...
January 5, 2017

Maths
for that pesky e notation: http://www.mathsisfun.com/numbers/scientific-notation.html look at example at the end: Example: 3.12E4 is the same as 3.12 × 104 3.12E4 = 3.12 × 10 × 10 × 10 × 10 = 31,200
January 5, 2017

Maths
Oh my, you really need another bit of spherical trig, namely the measure of an angle in "radians" there are 2 pi radians in a circle of 360 degrees so the circumference is C = 2 pi radians * R the handy thing is for any angle in radians now arc length along circle = ...
January 5, 2017

Maths
2*1.5 = 3 m^2
January 5, 2017

physics (mechanics)
dU = work done=potential change or force dr = dU U = A/r dU/dr = F = -A/r^2 Sign of A depends on attractive or repulsive.
January 5, 2017

Pre Calc
These are straight lines, they cross once. 2.4 +.3 t = 1.1 + .7 t .4 t = 1.3 t = 13/4 = 3 1/4 years
January 4, 2017

Math
pre tax = 1.18 p 1.18 p * 1.06 = 37.20 so p = 37.20 / (1.18*1.06)
January 4, 2017

math - calculus help!
oh well, not that hard V = (1/3)pi r^2 h r = 7 h/24 so V = (1/3)pi (7/24)^2 h^3 dV/dh = pi (7/24)^2 h^2 dh when h = 10 dV = pi (70/24)^2 dh dV = pi (35/12)^2 dh
January 4, 2017

math - calculus help!
You could use a fancy formula for volume of a cone and differentiate it to find dV/dh but if you just draw a picture you can see that the area of the surface * dh is the added volume for added dh
January 4, 2017

math - calculus help!
radius/depth = 7/24 what is radius when depth = 10? 7/24 = r/10 r = 70/24 = 35/12 now the change of volume with depth h is the surface area area * dh = dV pi r^2 dh = dV pi r^2 dh/dt = dV/dt = 12 ft^3/m pi (35/12)^2 dh/dt = 12 dh/dt = .449 ft/min
January 4, 2017

Pre calc
Good, you have two different ways now :)
January 4, 2017

Pre calc
slope = (20-13)/(4-3) = 7 also for any (x,y) slope = (y-20)/(x-4) so 7 = (y-20)/(x-4) 7 x - 28 = y - 20 so y = 7 x -8
January 4, 2017

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