Thursday

August 28, 2014

August 28, 2014

Total # Posts: 18,148

**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 :)
*April 8, 2014*

**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
*April 8, 2014*

**college alg.**

Different initial up speed but use : http://www.jiskha.com/display.cgi?id=1396965991#1396965991.1396967805
*April 8, 2014*

**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
*April 8, 2014*

**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 !!!! =
*April 7, 2014*

**Calculus Help Please!!!**

sin 2 x ---- 2 x + .... as x -->0 tan x also ---> x so 2x /(2x - x) 2x/x = 2
*April 7, 2014*

**Math**

least common multiple 8 = 2*2*2 30 = 5*2*3 so we need a 5, 3 twos, and a 3 so 120
*April 7, 2014*

**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
*April 7, 2014*

**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
*April 7, 2014*

**Physics**

use Google type 2.38 atm = Pascal get 2.38 atm = 241 153.5 pascals which is 241 Kilopascals
*April 7, 2014*

**Physic II**

300 g = .3 kg so .3 * .11 * 5 thousand calories
*April 7, 2014*

**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
*April 7, 2014*

**math**

505200000000000 = 505,200,000,000,000 = 505.2 * 10^12 = 5.052 * 10^14 so YES :)
*April 7, 2014*

**Fine number but what about it?**

What is the question
*April 7, 2014*

**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
*April 7, 2014*

**Math**

sin 2 x = sin x when x = 0, 180, 360 etc
*April 7, 2014*

**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
*April 7, 2014*

**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
*April 7, 2014*

**physics**

1) 90 - 42 2) 27 * 2
*April 7, 2014*

**I already answered this**

Please post once. Both are very wrong.
*April 7, 2014*

**Math**

You percent is percent that will FAIL It asks for the ones that do not fail.
*April 7, 2014*

**Math**

100 - 30.2
*April 7, 2014*

**Math**

Atta go :) You are welcome.
*April 7, 2014*

**Math**

dQ/dt = 200(-.0488) e^-.0488 t
*April 7, 2014*

**Math**

A = Ai e^-kt .5 = e^-14.2 k ln .5 = -14.2 k k = .0488 so Q = 200 e^-.0488 t
*April 7, 2014*

**Math**

Now I did problems very similar to this for you earlier. You try and I will check if I am around.
*April 7, 2014*

**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...
*April 7, 2014*

**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
*April 7, 2014*

**Calculus**

Tyler, if yu do not know how to use parentheses try to type it with lines like 1 -------- (3 t - 1) or something.
*April 7, 2014*

**Physics**

I am not going to look at this until I see some attempt by you to balance forces and moments.
*April 7, 2014*

**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
*April 7, 2014*

**World history**

Netherlands ? :)
*April 7, 2014*

**Math**

2.7^3 = 19.683 15 * 19.683 = 295.245
*April 6, 2014*

**statistics**

by the way that calculator uses x - mean for z instead of (x-mean)/sigma
*April 6, 2014*

**statistics**

Here is an online normal distribution calculator: http://davidmlane.com/hyperstat/z_table.html
*April 6, 2014*

**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 = ...
*April 6, 2014*

**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 ...
*April 6, 2014*

**Math**

.5 = e^-k T ln .5 = - k T T = -.693/-k = .693/k b) T = .693 / .0001074 = 6454 years
*April 6, 2014*

**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 :)
*April 6, 2014*

**Physics**

On earth I assume weight on first line = (86.4+20.8)(9.81) weight on second (lower) line = 20.8 (9.81)
*April 6, 2014*

**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
*April 6, 2014*

**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) ]
*April 6, 2014*

**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
*April 6, 2014*

**physics**

z = 5 * 10^5 ohms i = 1/(5*`10^6) = .2 *10^-6 = 2 *10^-7
*April 6, 2014*

**physics**

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/rlcser.html
*April 6, 2014*

**English**

B. ok C. Based on his very frail appearance, a mugger might SURMISE that he would be SUSCEPTIBLE to a strong arm attack; however, that would be a great mistake.
*April 5, 2014*

**English**

My version A. I said that he was HYPOCRITICAL because he pretends to be filled with PIETY, but I know that he is a bigger sinner than I am. I wouldn't even mind that if on Sundays in church he wasn't so POMPOUS.
*April 5, 2014*

**social studies check answers**

1. disagree 2. no idea 4. agree
*April 5, 2014*

**English**

loud and intense manner.
*April 5, 2014*

**algebra**

.25 A = 48 A = 48/.25 = 48 * 4 = 192 (2/3) 192 = 2 (64) = 128
*April 5, 2014*

**Read what you typed**

Lots of dimensions missing.
*April 5, 2014*

**Math**

ds = sqrt (dx^2 + dy^2) dx = -5sin t +5 sin5t dx^2= 25sin^2 t -50sint sin5t+25sin^2 5t dy = 5 cos t -5 cos 5t dy^2= 25cos^2 t-50costcos5t +25 cos^2 5t luckily sin^2 + cos^2 = 1 dx^2+dy^2=50-50(sin t sin 5t+costcos 5t) but sin a sin b + cos a cos b = cos(a-b) = 50 - 50 cos 4 t...
*April 5, 2014*

**Physics**

delta L/L = (T/area) / E = (215*9.81 /2*10^-5) / 8*10^10 = ( 1054 * 10^5 ) / 8*10^10 = 132 * 10-5 so delta L = (3.5)(132*10^-5) = 461 * 10^-5 = .00461 meters = .461 cm
*April 5, 2014*

**Physics**

Tension in cable = T Force up at end from cable = T sin 37 compression Force toward wall = T cos 37 max friction force = .485 T cos 37 up vertical forces on rod sum to 0 2 Fg = .485 T cos 37 + T sin 37 2 Fg = .989 T T = 2.02 Fg take moments about intersection of rod and wall ...
*April 5, 2014*

**Physics 141**

Hey. I just did that.
*April 5, 2014*

**Physics 141**

Distance axle above step edge = .33 - .125 = .205 Angle T is angle between straight down from Axle and the top edge of the step so cos T = .205/.33 T = 10.58 deg sin T = .184 Take moments about the top edge of the step. F * .205 clockwise (my step is on the right) m g * .33 ...
*April 5, 2014*

**Physics 141**

T = 1/4 so f = 4
*April 5, 2014*

**Physics 141**

after one period T, (8 pi T) = 2 pi so T = 1/4 so f = 1/T = 4
*April 5, 2014*

**math**

first .2*9.45 = 1.89 remaining length = 9.45 - 1.89 = 7.56 so piece 2 + (piece 2 - .12) = 7.56 2 * piece 2 = 7.68 piece 2 = 3.84
*April 5, 2014*

**Civil War**

It did sort of.
*April 5, 2014*

**strange question but**

You can easily figure out the velocity of each. It has nothing to do with the mass. (1/2) m v^2 = m g h note m cancels v = sqrt (2gh) so for example for 2.5 meters v = sqrt (2* 9.81*2.5) = 7 meters/second -------------------------- The only force here is gravity itself F = m ...
*April 5, 2014*

**physics**

(1/2) L i^2 = (1/2) C V^2 i^2 = (C/L) V^2 i^2 = (3.1*10^-6 / 5.6*10^-3) (961) i^2 = 532 * 10^-3 = 53.2 * 10^-4 i = 7.3 * 10^-2 = .073 amps
*April 5, 2014*

**physics**

period = 1/frequency = (1/7.01)*10^-18 wavelength = 3*10^8 (1/7.01)*10^-18 = .428 * 19^-10 = 4.28 * 10^-11 meters
*April 5, 2014*

**Statistics**

I also agree
*April 5, 2014*

**Pre calculus**

if it is x^3 + 2 x^2 - 15 x + 20 = 0 then: http://www.mathportal.org/calculators/polynomials-solvers/polynomial-roots-calculator.php gives x = -5.44 x = 1.72 +/- .853 i
*April 5, 2014*

**physics. PLEASE HELP**

If it is 50 meters high, the pressure is the weight of a one meter square column 50 meters high. Water density is about 1000 Kilograms/ cubic meter So the mass of this column is 1000 Kg/m^3 * 50 m * g or 1000 * 50 * 9.81 = 490,500 Newtons that weight is spread out over the one...
*April 4, 2014*

**Physics**

work done = increase in kinetic energy (here we have a decrease so the work is negative. The force is opposite to the direction of motion) work = (1/2)(4.5*10^4)(5000^2 - 7000^2) work = force *distance moved in direction of force so Force = work/(1.4*10^6)
*April 4, 2014*

**Physical science**

k Q1 Q2 / d^2 1) if d2 = 3 d 1 then 1/d^2^2 = 1/(3d1)^2 = (1/9) 1/d1^2 2) k Q1 (2 Q2)/d^2 = twice original
*April 4, 2014*

**speech-english**

I am tempted to just say model right off the bat but it depends on the audience and the setting. If it is a big crowd in an auditorium a model might not be very easy to look at from all angles and see inside it. Then photographs or a flip chart might be better. If the ...
*April 2, 2014*

**Physics**

original east momentum = 2115*10.61 final east momentum = (2115+3169)*5.03cos32.4 22440 = 5284 * 4.25 v = 22440 v v =1 m/s
*April 1, 2014*

**physics**

not of the mass itself, but about some other point. For example for a point mass hanging from a nail on a string it is m L^2 about the attachment point at the ceiling where L is the length of the string.
*April 1, 2014*

**Math (how do you find the volume of a cone)**

for any object with a point at the top and straight sides use (1/3) height * area of base
*April 1, 2014*

**Physics**

r = 1.5 * 10^-3 m pi r^2 = pi (2.25) * 10^-6 m^2 F/A = P = 2*10^4 /[pi (2.25) *10^-6) ] = .283 *10^10 = 2.83 * 10*9 Pascals
*April 1, 2014*

**Physics Help**

You have: velocity v = dx/dt = -A*ω*sin(ωt) so what is -A omega ? A = 3.5 omega = 2 pi f = .848 so - A omega = -2.968 or -2.97
*April 1, 2014*

**Geometry**

http://www.jiskha.com/display.cgi?id=1396301143
*March 31, 2014*

**Math probability**

4+7+3+2 = 16 socks prob red first = 4/16 prob green second = 7/15 prob that happens = (4*7)/(16*15) prob green first = 7/16 prob red second = 4/15 so again (4*7)/(16*15) so in the end 2 * 4 * 7 / (15*16) = .233
*March 31, 2014*

**Math**

1/51 I just answered this a few minutes ago.
*March 31, 2014*

**Geometry**

equation of circle radius 25 : x^2 + y^2 = 25^2 = 625 now what is x when 15 cm from center (which is ten cm from surface)? x^2 + 225 = 625 x^2 = 400 x = 20 that is our radius at urface area = pi (20)^2 = 400 pi = 1257 cm^2
*March 31, 2014*

**science(check answers)**

2 was wrong as were the others I mentioned more mass ---> more pull of gravity
*March 31, 2014*

**science(check answers)**

1 A true If you pick a hunk of iron up you want to be able to drop it when you get it to the place you want it. 2 b F = G M1M2/d^2 force proportional to mass 6 c the resistance has to go up to keep the same current R = V/i 7 d i reverses, B reverses
*March 31, 2014*

**math**

.9 x = 22,000 x = 22,000/0.9 = 24,444,44
*March 31, 2014*

**math**

if the pool is 76 feet long and each tile is 6 feet you need 13 tiles because 12 tiles only goes 72 feet However do you not need other rows of tile? This is a very strange question. Most tiles are about 6 inches, not six feet and they are square and you have to fit them in ...
*March 31, 2014*

**Math**

They would have to go 1296 miles in 7 days. 1296/7 miles/day 1296 / (7*24)miles/hour
*March 31, 2014*

**Math**

10/510 = .0196
*March 31, 2014*

**science(check answers)**

1.D yes 2.A yes 3.A yes 4.im not sure please help V = i R 12 = 4 R , R = 12/4 = 3 Ohms 5.false. I agree but am not sure what it means. One could always have a short circuit where current streams through doing nothing useful.
*March 31, 2014*

**Physics**

weight down = m g max friction force = mu m g centripetal force = m (lateral acceleration) mu m g = m a = m (.96 g) a = .96 g We call "lateral acceleration" centripetal acceleration :)
*March 31, 2014*

**Physics**

2.1) LOL - I would guess around mu = 0.96 2.2) 120,000 m/h * 1 h/3600 s = 33.33 m/s m v^2/R = .96 m g R = v^2/(.96 g) = 118 meters 2.3) mu = .8*.96 = .768 Normal F = m g cos 15 = .966 m g friction force = mu Normal = .768*.966mg =.742 mg component of weight down slope = m g ...
*March 31, 2014*

**Physical Sciences**

Type Mach 2 into Google and get back 681 m/s Ac = v^2/r = (681)^2/5800 = 80 m/s^2 80/9.81 = 8.15 g
*March 31, 2014*

**Calculus**

LOL, sketch a graph !
*March 31, 2014*

**Physics**

You are welcome :)
*March 31, 2014*

**Physics**

ke of ball at bottom = (1/2) m (2.44)^2 = 2.98 m Pe at top = m g h = m (9.81)(h) so 9.81 h m = 2.98 m h = .303 meters h = 1.47 (1 - cos theta) .303/1.47 = 1 - cos T .206 = 1 - cos T -cos T = -.794 T = 37.4 degrees
*March 31, 2014*

**physics**

(1/2)(4.008) V^2 = (1/2)(2500)(.037)^2 V = .924 m/s .008 Vb = (4.008)(.924 ) Vb = 463 m/s
*March 31, 2014*

**physics**

use conservation of momentum to get the velocity of the total mass (4.008 kg) just after collision in terms of bullet velocity Vb. Call that V. (1/2) m V^2 = (1/2) k x^2 that gives you V go back and get Vb
*March 31, 2014*

**Patterns and rules unit test 7th grade**

geometric sequeence a = -2 r = 6 An = a r^(n-1) A5 = -2 (6)^4 = - 2592 A6 = 6(-2592) = - 15552 A7 = 6 A6 = -93312
*March 31, 2014*

**Physics**

weight in air = 6400 * 9.81 volume of water displaced = 1 m^3 weight of water displaced = 1000 *9.81 *1 = 9810 N = force up from water tension = (6400 - 1000)(9.81) = 52,974 N
*March 31, 2014*

**Physics**

(1/2) m v^2 = .5 * .559 * 2.7^2
*March 31, 2014*

**statistics**

first one 12/45 second on 11/44 12/45 * 11/44
*March 31, 2014*

**physics**

a) v^2/R b) m v^2/R
*March 31, 2014*

**physics**

2000 u = 10 (200 cos 60 ) u = cos 60
*March 30, 2014*

**physics**

1500 * 20 = (1500+m)10 m = 1500
*March 30, 2014*

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