Friday

April 18, 2014

April 18, 2014

Total # Posts: 16,151

**Physics**

2 cars pulling together on level surface? Mass of cars = 3800 kg weight of cars = 3800*9.81 = 37278 N so max friction force of tires = 37,278 N mass of full vault =38803 kg weight of full vault = 380,657 N max retarding friction = .57*380657 = 216,974 N In other words, based o...

**History HELP! ASAP**

Each of your questions requires an essay to help you and perhaps if you try to write them someone here can help with them. In this case I might concentrate on the interaction of England, France, US colonies and Iroquois and Algonquins. In the other question I would discuss rea...

**science**

m g h = Potential energy at top = 822 60 (9.81) h = 822 h = 1.4 meters

**calculus help**

https://www.wolframalpha.com/input/?i=derivative+of+x^2%28x%2B3%29%2F%28x%2B1%29^3 6x / (x+1)^4

**calculus help**

then do it again :)

**calculus help**

[(x+1)^2 (3 x^2)-x^3 (2)(x+1)] /(x+1)^4 [(x+1)(3x^2) - 2 x^3 ]/ (x+1)^3 [ 3 x^3 + 3 x^2 -2 x^3 ] / (x+1)^3 [ x^3 + 3 x^2] /(x+1)^3 x^2 (x+3) / (x+1)^3

**calculus help**

https://www.wolframalpha.com/input/?i=derivative+of+%28x^3%29%2F%28%28x%2B1%29^2%29+

**Math**

how many cups in a gallon? 16 so 2 cups concentrate + 16 cups water = 18 cups lemonade so concentrate / lemonade = 2/18 = 1/9 now how many ounces in a pint (a pint is a pound the world around :) 16 so 1/9 =x/16 x = 16/9 = 1.78 oz

**SS**

Build factories, farms, houses providing residents with jobs.

**calculus help**

Play with this: https://www.wolframalpha.com/input/?i=derivative+of+1%2B%281%2Fx%29%2B%285%2Fx^2%29%2B%281%2Fx^3%29+

**Optics - sorry, not I **

sorry, optics is not my thing at all :(

**calculus help check and help**

a) calculate lim t->infinity (v. answer: mg/c ----->what is the meaning of this limit ============================== It is the "terminal velocity" (Google that) which is the speed where the drag force equals the weight. One uses a parachute so that one's te...

**physics**

a = change in velocity/time = (0 - 43)/.28 = - 154 m/s^2

**Geometry**

for similar figures areas scale with the square of lengths so sqrt(4/49) = 2/7

**math**

1.025^10 = 1.280084544 * 5000 = 6400.42

**calculus**

http://www.mathsisfun.com/data/function-grapher.php f' = 7 e^7x - e^-x when is that zero? 7 e^7x = e^-x 7 e^8x = 1 e^8x = 1/7 8 x = ln(1/7) x = -.243 at min

**calculus help**

try : https://www.google.com/search?q=graph+ln%28x%29+from+1+to+6&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb ln 6 = 1.79 ln 1 = 0 ln 6 - ln 1 = 1.79 1.79/5 = .36 approx ln x = .36 e^ln x = ? = e^.36 so x = 1.43 sure enough between 1 and 6 :)

**Algebra**

2 (a+1) / [(a+1)(a-1)] for starters :)

**Geometry- trig ratio**

sin 55 = 21,000/hypotenuse we want that hypotenuse

**science**

you want traction, not slipping, so increase friction.

**Math**

sin 10 = PR/16 PR = 16 sin 10

**Algebra**

You are welcome. You could have done this by long division but often you can see the factors more quickly.

**Algebra**

2 x^3 – x^2 – 24 x + 12) = (2 x^3 -24 x) - (x^2 - 12) = 2 x (x^2-12) - 1 (x^2-12) = (2x-1)(x^2-12) now divide that by (2x-1) :)

**Math**

sin 10 = PR/16 PR = 16 sin 10

**Math**

1.05^2 - 1 = 10.25 APY Wilder 1.0081666^12 - 1 = 10.2524 APY Cheapskate so go with cheapskate ten years 1.05^20 =2.6532 *85,000 = 225,530.30 1.0008166667^120 = 2.65387 *85,000 = 225,579.18 Cheapskate is 48.88 better

**english**

The magnificent king emerged victorious eliciting a groan from his opponent who had been deserted by his muses depriving him of the strength of his convictions :-)>

**Geometry - Area**

You are welcome :)

**Geometry - Area**

find the area of each of the 6 equilateral triangles making up the hexagon Each side of triangle = 12 yards { by the way, first check apothem length because it is our altitude ) tan 30 = (1/2)(12)/apothem apothem = 6/tan 30 = 10.4 - sure enough, whew } so area of triangle = (1...

**math**

5 * .011 * p = 82.5

**math**

10 * .025 * 5000 5000 + part A (ignoring inflation :)

**chemistry**

Use google for conversion 1500 mm Hg = 1.97368421 atm = 199 983.553 pascals

**Algebra II**

In other words you did one of 120 sequences that yield 7 successes out of 10 trials.

**Algebra II**

....but the probability of failure is not independent of the probability of success :)

**Algebra II**

binomial distribution p(sucess) = 12/15 = 4/5 = .8 1-p = 1/5 = .2 n = 10 k = 7 P(x=7) = C(10,7) * .8^7 * .2^3 C(10,7) = 10!/[ 7! (3!) ] = 10*9*8 / (3*2) = 80*9/6 = 120 so P = (120)(.8^7)(.2^3) = 0.201

**geometry**

100 = 4x^2 25 = x^2 x = 5 or -5 but if you really want to use formula x^2 + 0 x - 25 = 0 x = [ -0 +/- sqrt (0 + 100) ] / 2 x = +/- 10/2 x = +/- 5

**math (matrix)**

I assume you meant the determinant 24 x + 3 x^2 + 6 x + 10 - 9x = 25 3 x^2 + 21 x -15 = 0 x^2 + 7 x - 5 = 0 x =-7/2 +/- (1/2) sqrt(69) What a mess, assume you have a typo. To invert matrix use http://matrix.reshish.com/inverse.php

**math**

100 * (1/8)/ (8/12+3/12) = 100 * (1/8) / (11/12) = 100 * (3/24)(22/24) = 100 (3/22) = 13.6%

**Calc III**

not a valid transformation, zeros on diagonal check with http://www.wolframalpha.com/widgets/view.jsp?id=d6a52679e750c30e320a7094ec975598

**math**

pi D = 3.14159 * 13

**math**

1" = 50 miles IS 2" = 100 miles so if 2" is only 25 miles, we will need four times as long a sheet of paper. so 4

**whoops, arithmetic error**

t^2 - 2 t - 3 = -(1/5)(h) t^2 - 2 t = -h/5 + 3 t^2 - 2 t + 1 = -h/5 + 4 (t-1)^2 = -(1/5) (h - 20) so max height at one second of 20 meters

**Math 10**

that is a parabola (quadratic) 5 t^2 - 10 t - 15 = -h find the vertex by completing the square t^2 - 2 t - 7.5 = -(1/5)(h) t^2 - 2 t = -h/5 + 7.5 t^2 - 2 t + 1 = -h/5 + 8.5 (t-1)^2 = -(1/5) (h - 42.5) so max height at one second of 42.5 meters

**math**

r = 24 in /gift * 1 yd / 36 in * number of gifts r = (24/36) * number of gifts cost = 2 * r

**math**

10 apples/basket 2 baskets/bushel so 20 apples per bushel min 900/20 = 90/2 = 45

**math**

number of cuts = (n-1) amount wasted = 1/16 * (n-1) amount total = (3/32) n + (1/16) n - 1/16 so 25 16/32 = 5 n/32 -2/32 816/32 +2/32 = 5 n/32 818 = 5 n n = 163.6 so 163

**free-body diagram help**

You only need the horizontal forces in this case because the friction force(not the coefficient) is given. 45 - 13 = 20 a work done = change in kinetic energy = (45 - 13) (4) Newton meters or Joules

**Physics**

weight of ladder = m g = W force down on floor = W max friction force = .3 W so horizontal force on top of ladder from wall = . W Take moments about base of ladder .3 W (L sin T) = W(L/2)cos T .3 sin T = (1/2) cos T tan T = .5/.3 T = 59 degrees Notice that the ladder length do...

**maths**

1.875 km * 2 * 6 = 22.5 km

**Maths**

3 a = 4 2 a = -3 there is only one variable here, a there is no intersection of lines so no solution by elimination or substitution: a = 4/3 for the first equation a = -3/2 for the second equation

**Math**

Very interesting but as far as I know these are your apparel dimensions. I do not read minds and have no idea what you are looking at. Is it a triangle maybe?

**math PLEASE HELP!!!!!**

girth = 2(32+49) = 162 times length 41 = 6642 ft^2 base area = 32*41 = 1312 times height = 64288 ft^3 Why on earth do you need a formula? Draw a picture.

**Circle Geometry**

draw a picture line from center of circle to tack hits circumference at a right angle (because it is a radius) and therefore that is the closest point to the tack. also line from circle center to ground is 90 deg so right triangle d is hypotenuse center to tack r^2 + 58^2 = d^...

**Calculus Help Please!!!**

Q = Qi e^-k t when Q/Qi = 1/2 .5 = e^-k t ln .5 = - 4 k so k = (ln .5) / -4 Q = 800 e^ (ln .5)t / 4 k = .1733 so Q = 800 e^-.1733 t if t = 30 Q = 800 e^-5.2 Q = 4.4 mg 1/800 = e^-.1733 t ln(1/800) = -.1733 t 38.6 days enough already

**Physics multiple choice questions**

Ah, first you try and it is too late because I have to go to sailing practice. Maybe Steve will help.

**Calculus Help Please**

ln x y = lnx + ln y ln x + ln y -cos^-1(x-1) = x 1/x + (1/y) dy/dx+(1/[1-(x-1)^2])^.5 = 1 1/x +(1/y)dy/dx+(1/(-x^2+2x)^.5) = 1 (1/y) dy/dx = 1 - 1/x - [1/(x(2-x))^.5 dy/dx = y { 1 - 1/x - [1/(x(2-x))^.5 } when x = 1 ln x + ln y -cos^-1(x-1) = x 0 + ln y - pi/2 = 1 ln y = 1 + p...

**Physics**

east is + 1500 * 25 - 2000 * 0 = 3500 v

**Physics**

change in momentum of car A = 1250 (40) = 50,000 toward the west so change in momentum of car B is 50,000 toward the east 50,000 = 2000 (east velocity - -25) 25 = east velocity + 25 east velocity = 0 stopped it dead in the water :)

**physics**

change in temp = 90 - 15 = 75 deg C heat in = mass * specific heat * change in temp = 12 kg * specific heat * 75 deg C I do not know specific heat in Joules or calories or kilocalories or whatever you are using in your class / kilogram deg C

**college alg.**

Different initial up speed but use : http://www.jiskha.com/display.cgi?id=1396965991#1396965991.1396967805

**college algebra**

h = hi + Vi t - (1/2) g t^2 in ancient English units this is h = Hi + Vi t - (1/2) 32 t^2 If Hi = 0 Vi = 128 ft/s then h = 128 t - 16 t^2 for h = 144 144 = 128 t - 16 t^2 16 t^2 - 128 t + 144 = 0 t^2 - 8 t + 9 = 0 t = [ 8 +/- sqrt(64 -36) ]/2 t = 4 +/- sqrt 7 t = 1.35 t = 6.65

**Calculus Help**

y = sin [ pi*(t^2+5)^-.5 ] y' = pi [cos pi*(t^2+5)^-.5] * [-.5(2t)](t^2+5)^-1.5 if t = 2 y' = pi {cos pi/ 3} *[-2] [ 1/27 ] = -(2pi/27) cos (pi/3) but cos pi/3 = 1/2 so -pi/27 CHECK MY ARITHMETIC !!!! =

**Calculus Help Please!!!**

sin 2 x ---- 2 x + .... as x -->0 tan x also ---> x so 2x /(2x - x) 2x/x = 2

**Math**

least common multiple 8 = 2*2*2 30 = 5*2*3 so we need a 5, 3 twos, and a 3 so 120

**math word problem PLEASE HELP**

r = ribbon = 15 (5 3/8) - 10(3/4) r = 15 (43/8) - 60/8 r = (15*43 - 60 )/8 = 585/8 = 73 1/8 yards

**Physics**

Or approximate in your head 1 atm = 10^5 Pascals approx so 2.38 atm = about 2.3 *10^5 pascals which is 2.3 * 10^2 kilopascals or 230

**Physics**

use Google type 2.38 atm = Pascal get 2.38 atm = 241 153.5 pascals which is 241 Kilopascals

**Physic II**

300 g = .3 kg so .3 * .11 * 5 thousand calories

**chemistry**

.75 * .5 = .375 mols of Na2CO3 2 HCl + Na2CO3 --> 2 NaCl + H2O +CO2 so we need .375 * 2 = .75 mols of HCl .75 * 1.25 = .9375 Liters

**math**

505200000000000 = 505,200,000,000,000 = 505.2 * 10^12 = 5.052 * 10^14 so YES :)

**Fine number but what about it?**

What is the question

**Chemistry**

Yes, but Mols of H2SO4 in ONE LITER 3 M means 3 mols in a liter 9 M means 9 mols in a Liter

**Math**

sin 2 x = sin x when x = 0, 180, 360 etc

**science/math**

1. No If it hits at 42 from the SURFACE that is 90-42 = 48 from the normal. The reflected ray will also be 48 from the normal. 2. NO 27 + 27 = 54

**Physic II**

sh in cal/kg deg C = .19 *1000 = 190 heat in = mass * sh * delta T 450,000 = 100 * 190 * (50-T) 23.68 = 50-T T = 26.3 deg C

**physics**

1) 90 - 42 2) 27 * 2

**I already answered this**

Please post once. Both are very wrong.

**Math**

You percent is percent that will FAIL It asks for the ones that do not fail.

**Math**

100 - 30.2

**Math**

Atta go :) You are welcome.

**Math**

dQ/dt = 200(-.0488) e^-.0488 t

**Math**

A = Ai e^-kt .5 = e^-14.2 k ln .5 = -14.2 k k = .0488 so Q = 200 e^-.0488 t

**Math**

Now I did problems very similar to this for you earlier. You try and I will check if I am around.

**Math**

You sure are having quite a time with these exponential functions! y = 190 [ 1- .955 e^-(.25 t) ] If t = 9 y = 190 [ 1 - .955(.105) ] = 190 [ 1 - .1 ] = 171 cm In other words it has reached 90% of max length in 9 years now dy/dt = 190(-.955) (-.25)(.105) = 4.76 cm/year c) when...

**Physics**

a) Vx = 65 cos 30, Vy = 65 sin 30 b) Vx =125 cos 40, Vy = -125 sin 40 c) Vx = 5.3 sin 30 , Vy = 5.3 cos 30 of course sin 30 = 1/2 and cos 30 = sqrt3/2

**Calculus**

Tyler, if yu do not know how to use parentheses try to type it with lines like 1 -------- (3 t - 1) or something.

**Physics**

I am not going to look at this until I see some attempt by you to balance forces and moments.

**physics**

Pick some time over which the dB/dt takes place, say t = one second. Then dB/dt = 3.2/1 = 3.2 T/s then you can get i for that dB/dt then i * t = i * one second

**World history**

Netherlands ? :)

**Math**

2.7^3 = 19.683 15 * 19.683 = 295.245

**statistics**

by the way that calculator uses x - mean for z instead of (x-mean)/sigma

**statistics**

Here is an online normal distribution calculator: http://davidmlane.com/hyperstat/z_table.html

**statistics**

well, you have enough data points to use normal distribution rather than computing with binomials forever and a day. Otherwise use a program or spreadsheet to compute all the binomial coefs and powers and products mean = n p = 200 * .6 = 120 sigma^2 = 120 (.4) = 48 so sigma = ...

**Math**

we have already done a half life one but anyway ds/dt = k s ds/s = k dt ln s = k t + c when t = 0, ln si = c si is initial size ln s = k t + ln si ln (s/si) = k t s/si = e^kt 2 = e^k(30 min) ln 2 = 30 k k = .0231 1,000,000/50 = e^.0231 t ln (20,000) = .0231 t t = 428.6 = 429 m...

**Math**

.5 = e^-k T ln .5 = - k T T = -.693/-k = .693/k b) T = .693 / .0001074 = 6454 years

**physics**

1 C 2 less, maybe you run over the mark from the first one on the track just as the rear can explodes, and the two marks on the track are together :)

**Physics**

On earth I assume weight on first line = (86.4+20.8)(9.81) weight on second (lower) line = 20.8 (9.81)

**physics**

in the horizontal direction the ball has no acceleration once let go (no horizontal force) so now it is 9 m/s^2 down by the way, g on Mars about the same as earth ? FALSE

**physic**

40 g = .04 kg .04 [25 (sh ice) + heat of fusion + 100 (sh water) + heat of vaporization + 5 (sh water vapor at 1 atm) ]

**algebra 2**

An = A1 + (n-1)d average = (A1 + An)/2 sum = average * number of terms = n (A1 +An)/2 = (n/2) [ 2 A1 + (n-1)d ] here = (11/2) [ -24 + (10)5 ] = (11/2) (26) = 11 * 13 = 143

**physics**

z = 5 * 10^5 ohms i = 1/(5*`10^6) = .2 *10^-6 = 2 *10^-7

Pages: **1** | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | Next>>