# Posts by Damon

Total # Posts: 30,122

Physics
Oh, I see, the force is forever a = F/m = 5/2 = 2.5 m/s^2 10 = (1/2) a t^2 20 = 2.5 t^2 t = 6.93 seconds V = a t = 2.5 *6.93 = 17.3 m/s

for how long?
How long was the force in contact with the ball? Force * time = change in momentum = m v

Math
.015 mols/liter * .01 liter = .15 mols = .00015*332 = .0498 agree

Maths
http://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html a3 = a1 + 2 d = 90 a11 = a1 + 10 d = 50 -----------------------subtract a3-a11 = 0 -8 d = 40 so d = -5

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)

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

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

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

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 ...

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

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)

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

The cay is the book
C is the only choice that indicates determination.

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 ...

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

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

maths
3.14159.... is between 3 and 4

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

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

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.

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

math
c = 3(c+3) -3(c-3) c = 3 c + 9 - 3 c + 9 c = 18

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

error
2 a - 62 = 12 2 a = 74 !!!!! a = 37 b = 25 same answer anyway

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

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)

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

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

We are teachers. We do not do tessts for people.

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

physics
weight = w = m g normal force = m g cos theta ratio = cos theta so cos 17 and cos 30

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

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 ...

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

calculus
two negative numbers can not add to +1

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

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

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 :)

physics
The earth moves under your feet (but just a little).

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!

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

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...

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

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

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 ...

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 = ...

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

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

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

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

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

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

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 ...

Algebra 1
You are welcome.

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

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

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

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

Algebra 2
You are welcome.

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 (...

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?

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.

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?

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 ...

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.

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

Algebra 1
You are welcome.

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

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

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

algebra
3 z^2 = -108 z^2 = -36 z = +/-6 sqrt -1 = +/- 6i

algebra
5 x^2 = 651-536 = 115 x^2 = 23 x = +/- sqrt 23 = +/- 4.80

Math
49 - 2v

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

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

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)

Chemistry
Ph determination

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

Math
(2*27 + n)/3 = 29 54 + n = 87 n = 33

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)

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

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

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)

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

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

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

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

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

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

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:)

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.

Maths
Clearly parallax is not a problem at this distance :)

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 ...

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

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 = ...

Maths
2*1.5 = 3 m^2

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.

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

Math
pre tax = 1.18 p 1.18 p * 1.06 = 37.20 so p = 37.20 / (1.18*1.06)

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