Thursday

September 3, 2015
Total # Posts: 21,884

**mechanics: spring problem**

In total the block fell from 3 to 1 meters off floor so change in gravitational potential m g h = m g (2) there it is stopped so that energy is now stored in the spring which compressed half a meter m g (2) = (1/2) k x^2 = 80 (1/4) = 20 so 20 m = 20 m = 1 kg
*September 3, 2015*

**mechanics: spring problem**

I just did one problem from you, the xo and vo sping
*September 3, 2015*

**Physics**

Initial ke = (1/2)(.05)(400)^2 Final Ke = (1/2)(.05) (50)^2 so work done = (1/2)(.05)( 400^2-50^2) = force * distane = 40,000 T solve for T
*September 3, 2015*

**Pre Calculus**

V = 4.50 (t-5) + Vi where Vi is the initial 2005 value
*September 3, 2015*

**mechanics: simple harmonic oscillation**

x = a sin w t + b cos wt v = a w cos wt - b w sin w t omega = w = sqrt(k/m) at t = 0 x = -xo v = dx/dt = vo - xo = b + vo = a w or a = vo/w so x = (vo/w) sin w t - xo cos wt now I could say magnitude (or amplitude) = sqrt (vo^2/w^2 + xo^2) which is max motion from equilibrium...
*September 3, 2015*

**Algebra**

The y intercept is where the line hits the y axis. That is when x = 0 so y = 0 x + b = b The x intercept is where the line hits the x axis. That is when y = 0 0 = a x + b so x = -b/a (That is why a can not be equal to 0. If it were the x axis intercept would be undefined. This...
*September 3, 2015*

**Elementary Euclidean Geometry(Math)**

Elementary Logic :) hypothesis - if a cow, then a mammal if true then converse - if a mammal then a cow Not sure ( It is the converse we have here :) inverse - if not a cow, then not a mammal Not sure contrapositive - if not a mammal, then not a cow True.
*September 2, 2015*

**ALGEBRA**

7 x^2 + x^2 = 8 x^2
*September 2, 2015*

**Pre-Calc**

Looks good to me. All you really have to do is remember that pi radians = 180 degrees.
*September 2, 2015*

**Pre-Calc**

-780 + 360 = -420 once around -420 + 360 = -60 twice around -60 + 360 = 300 sure enough
*September 2, 2015*

**Math ?**

I have no idea.
*September 2, 2015*

**Math**

If you replace, then the drawings are independent. 16 + 11 + 9 + 15 + 8 + 20 = sum green = 15 so p(green) = 15/sum
*September 2, 2015*

**MATH**

Oh, and remember that sum of angles in parallelogram is 360
*September 2, 2015*

**MATH**

3 x + 2 x + (3/2) x = 180 now try
*September 2, 2015*

**ALGEBRA**

7 x^2 + x^2 = 8 x^2 The first one was correct.
*September 2, 2015*

**ALGEBRA**

8 x^2 - 5 x + 1.5 y
*September 2, 2015*

**Astronomy**

You walk faster than you run, typoo I think 15 min * 60 s/min = = 900 seconds 12 min * 60 s/min = 720 seconds You spent 1620 seconds on this crazy trip You went 900*3.8 = 3420 720*2.5 = 1800 so 5220 meters 5220meters/1620seconds = 3.22 m/s
*September 2, 2015*

**factorisation i need cerious itz too difficult**

sorry (x^2 + y^2)
*September 2, 2015*

**factorisation i need cerious itz too difficult**

Try dividing by (x^2 + 2 y^2)
*September 2, 2015*

**precalc**

3) slope = m = 2 5 = 2*2 + b b = 1 so y = 2 x + 1 4) slope = m = -1/1 = -1 so y = -x + b 4 = 2 + b b = 2 so y = -x + 2
*September 1, 2015*

**math**

1166 2/3 I mean
*September 1, 2015*

**math**

Now you know the math way and the science way :)
*September 1, 2015*

**math**

1 3/4 = 7/4 inch 7/4 inch*(500 miles/.75 inch) = 1167 2/3 miles 14" (500mi/.75") = 9333 1/3 mi etc
*September 1, 2015*

**Math**

12.6666666666..... is greater than 12.63
*September 1, 2015*

**algebra**

well, try 84 (80 + 88 + x)/3 = 84 168/3 + x/3 = 84 168 + x = 252 x = 84 of course since that was original average now 89 80 + 88 + x = 3*89 = 267 168 + x = 267 x = 99 so 84 </= x </= 99
*September 1, 2015*

**simultaneous equation very dificult need help itz urgent**

a - c = b/2 a -c/6 = b -------------- subtract -5c/6 = -b/2 b = 5 c/3 so 5 c/3 + c = 32 8 c/3 = 32 c = 12 your turn
*September 1, 2015*

**alGEBRA 1**

10 days * 24 h/d = 240 h 240 h * 60 min/h = 14,400 min
*September 1, 2015*

**Chem**

mass of acid = 11.299-5.333 grams density = mass/volume = (11.299 - 5.333) g / 5 mL
*September 1, 2015*

**MAT 221**

nah d/6
*September 1, 2015*

**Choctaw Middle School**

3(16) + 4(10) = 48 + 40 = 88
*September 1, 2015*

**Math**

c = m h + b 55 = m (2) + b 65 = m (3) + b ------------------subtract -10 = -m m = 10 c = 10 h + b 55 = 20 + b b = 35 so c = 10 h + 35 if h = 6 c = 60 + 35 = 95
*September 1, 2015*

**Travis elementary school**

123 :)
*September 1, 2015*

**Maths**

5500 = 495 x - 475 x + 4950 550 = 20 x x = 27.5
*September 1, 2015*

**Maths**

x*475 + 10*550 = (x+10)*495
*September 1, 2015*

**math**

a numerical amount.
*September 1, 2015*

**Physic**

That's better R for 2 and 3 in parallel = 2*3/2+3 = 6/5 as we said before If 4 ohm is in series with those then add R total R = 6/5 + 4 = 26/5 current through 4 ohm = all of it = 20/R = 20*5/26 = 100/26 = 3.85 amps voltage across 4 ohm = 3.85*4 =15.38 V voltage across two ...
*September 1, 2015*

**voltage?**

1/2 + 1/3 = 1/R 3/6 + 2/6 = 5/6 so R = 6/5 Ohms now I have no idea what the 4 is. Another R in series? What is the voltage across what ?
*September 1, 2015*

**math**

500/3.3 = 151.5 miles per hour 300/2.5 = 120 miles/hour
*September 1, 2015*

**Math**

slightly different numbers, same problem http://www.jiskha.com/display.cgi?id=1441141046
*September 1, 2015*

**Math**

I just did this :(
*September 1, 2015*

**Algebra**

no x + 2 (2) = 3 x = -1
*September 1, 2015*

**Algebra**

multiply firat equation by 4 4 x + 8 y = 12 4 x + 5 y = 6 ----------------subtract 3 y = 6 y = 2 etc
*September 1, 2015*

**Algebra**

x axis intercept when y = 0 3/4 x = 3 x = 4 y axis intercept when x = 0 y = 3
*September 1, 2015*

**math**

a) 3, 4 , 5 is a common right triangle b) will not quite work 3 is long side 1 + 2 just barely stretches from end to end, just making a thicker three inch line :) c) misses by an inch. 7 + 12 = 19 which will not reach from end to end of 20 d) sure, why not - draw it
*September 1, 2015*

**math**

they have to add up to 8/8
*September 1, 2015*

**Math**

probability of first green = 8/20 probability of second green = 7/19 so (8/20)(7/19)
*September 1, 2015*

**math**

24 + 2 Z = ?
*September 1, 2015*

**Pre-Calculus**

eg https://www.khanacademy.org/math/algebra2/conics_precalc/parabolas_precalc/v/using-the-focus-and-directrix-to-find-the-equation-of-a-parabola
*September 1, 2015*

**Pre-Calculus**

This is a pure cookbook question and just follow the procedure in your text. We are here to help if you get stuck, not to do it for you.
*September 1, 2015*

**Pre-Calculus**

I already took the subject. You try.
*September 1, 2015*

**Math**

You are welcome.
*August 31, 2015*

**Math**

do it in seconds (30/26.2)( 1*3600 + 18*60 + 27) seconds = (30/26.2) (4707 seconds) = 5390 seconds take off one hour which is 3600 seconds 1 hour and 1790 seconds note 1790/60 = 29.83 so take off 29 minutes which is 1740 seconds 1 hour and 29 minutes and (1790-1740)seconds so ...
*August 31, 2015*

**no table**

pasting here does not work and we can not see your table of arrivals and departures.
*August 31, 2015*

**U.S. History**

They also tended to find good harbors, particularly at the mouths of rivers which gave them access to the interior. This was before the age of railroads, cars, trucks and planes so the fast and easy way to get around was by boat even if you did not have to take heavy cargo ...
*August 31, 2015*

**math**

0.25 is indeed 1/4
*August 31, 2015*

**Algebra**

a, b , c a+b+c=180 a = c/4 b = c-36 so c/4 + c-36 + c = 180 2.25 c = 216 c = 96 b = c-36 = 60 a = 24
*August 31, 2015*

**Siyabusa secondary**

for example see: http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/idegas.html
*August 31, 2015*

**Siyabusa secondary**

at stp one mol is 22.4 liters so 1.5 mol is 1.5 * 22.4 = 33.6 Liters
*August 31, 2015*

**maths**

Three out of every five are boys. 3/5 = x/40 multiply both sides by 40 8 * 3 = x x = 24 ========================== check that means 40 - 24 = 16 are girls 24/16 = 12/8 = 3/2 sure enough
*August 31, 2015*

**typo**

It is not 0.5 meter square Volume must be in meters CUBED It is probably a cube. but from what you wrote I can not say if you mean a cube with a square base with sides of 0.5 meter In which case we would have V = .5^3 = .125 m^3 or perhaps you mean V = 0.5 m^3 in either case V...
*August 31, 2015*

**Math**

Altitude h = 12 I think on one side you have a 5, 12, 13 right triangle and on the other a 9 , 12 , 15 right triangle (a 3,4,5 times 3) so average base = (11+25)/2 = 18 altitude = 12 area = 12 * 18
*August 31, 2015*

**Algebra**

agree
*August 31, 2015*

**physics**

The speed is horizontal at the top, call it u and it remains u all the way down because there is no horizontal force (acceleration). So we have a vertical problem first. v = g t h = (1/2) g t^2 so 33.2 = 4.9 t^2 t^2 = 6.77 t = 2.60 seconds so v = 9.81 * 2.6 = 25.5 m/s down ...
*August 31, 2015*

**link better**

http://www.google.com/search?q=hydrogen+radiation+spectrum+transitions&tbm=isch&tbo=u&source=univ&sa=X&ved=0CEwQsARqFQoTCO_83vy_08cCFcgyPgodLu8DCw&biw=1920&bih=971#imgrc=84jXbb3JhPIc3M%3A
*August 31, 2015*

**CHEMISTRY**

Here: https://www.google.com/search?q=hydrogen+radiation+spectrum+transitions&tbm=isch&tbo=u&source=univ&sa=X&ved=0CEwQsARqFQoTCO_83vy_08cCFcgyPgodLu8DCw&biw=1920&bih=971#imgrc=84jXbb3JhPIc3M%3A Look at all possible ways from 4 down to 1 such as 4 - 3 - 2 - 1 or 4 - 2 -1
*August 31, 2015*

**Plus**

10* 569 = 5690 2 * 569 = 1138 add those 12* 569 = 6828
*August 30, 2015*

**Math**

10 * 20 * 500 = 200 * (1,000/2 ) = 100 * 1,000 = 100,000
*August 30, 2015*

**Science - physics**

average speed during stop = 122/2 = 61 m/s to get time to stop v = 0 = 122 - 6.2 t t = 122/6.2 = 19.7 seconds so distance = v average * t = 61*19.7 = 1200 meters Off the end of the runway and 200 meters into the bleak ocean
*August 30, 2015*

**Calculus**

f' = sec x tan x + 2 sin x at x = pi/3 which is 60 deg f' = m = (2 * sqrt 3) + 2 (sqrt 3/2) so m = 3 sqrt 3 so y = 3 sqrt 3 * x + b at (pi/3 , 1) 1 = 3 (pi/3) sqrt 3 + b b = 1 - pi sqrt 3 so y = (3 sqrt 3) x + (1-pi sqrt 3) or approx y = 5.20 x - 4.44
*August 30, 2015*

**Calculus**

nothing wrong with that
*August 30, 2015*

**MATH ALGEBRA**

x = number of trees at year n at year 0, x0 = 7000 at year 1, x1 =.88*X0 + 600 = 6160+600 = 6760 at year 2, x2 = .88*x1 +600 = 6548.8 at year 3 , x3 = .88x2+600 = 6362.9 at year 4, x4 = .88*x3 + 600 = 6199.4 at year 5, x5 = .88*x4+600 = 6055.5 at year 6, x6 = .88*x5+600 = 5928...
*August 30, 2015*

**math calculus**

typo in second line .7 = e^-40 k
*August 30, 2015*

**math calculus**

a = A e^-kt .3 = e^-40 k ln .7 = -.357 = -40 k k = .008917 so 1/2 = e^-.008917 t if t is half life ln .5 = - .693 = -.008917 t t = 77.7 hours
*August 30, 2015*

**math**

Been there, done that: http://www.jiskha.com/display.cgi?id=1440890314
*August 30, 2015*

**Calculus**

If this is y = [ x^4 + x ]^.5 ?????? dy/dx = .5 [ x^4 + x ]^-.5 (4x^3 +1) = .5 (4x^3+1) /sqrt(x^4+x) ================================= if you mean y =( x^.5 )(x^3+1) y = x^3.5 + x^.5 dy/dx = 3.5 x^2.5 + .5 x^.5 /x = x^.5 ( 7 x^2 + 1/x)/2 = x^.5 (7 x^3 + 1) /(2 x) = (7 x^3 + 1...
*August 29, 2015*

**Physics**

Bug dv/dt = ab = 60 mi/h/2.4s = 25 mi/(s h) = 40.2 km /(3600 s^2) Sal dv/dt = as = 60/2.8 = 21.4 mi/(s h) =34.4 km/3600s^2 v = 75 km/h = 75 km/3600s then v = a t or t = v/a Bug: t = 75 km/3600 s / 40.2 km/3600s^2 = 1.87 seconds d = (1/2) a t^2 = OR use half max (average) speed...
*August 29, 2015*

**SCIENCE!**

1. - Did the rock chip hit him in the eye? 2. what mistake did Andrew make using measurement units? for density he needs VOLUME, not distance. He measured centimeters. He needs centimeters CUBED or cm^3 or cc 3. yes, write it in your lab notebook ! 4. I think he determined the...
*August 29, 2015*

**math**

I will try to reverse engineer what you are doing because I am not sure I understand you Say we are doing a compound interest problem. Yearly interest rate as a decimal is r For example 5% is .05 then every year I multiply what I have is the amount from the year before + r ...
*August 29, 2015*

**Math**

s^2 + 1 = (1/2)(4s) s^2 - 2 s + 1 = 0 (s-1)(s-1) = 0 s = 1
*August 29, 2015*

**math**

for exponential growth (continuous compounding) amount = original * e^rt rate = -.02 or -2 percent for example if you have ten dollars then after one year you will have 10 e^-.02 = 10(.980298) = nine dollars and eighty cents so each year multiply by .98 NOT 1.98 BUT that is an...
*August 29, 2015*

**Geometry**

5p^2-23p+24 well 24 = 4*6 or 3*8 or 2*12 or 1*24 so what might work in ( 5 p - %%) (p - %%) 15 and 8 is 23 so try 3*5 and 8 (5 p - 8)( p - 3 )
*August 29, 2015*

**math**

r = 0.06 meters A = pi r^2 F = 350,000 Newtons p = F/A = 350,000 /(pi *.06^2) in Newtons per square meter which is Pascals
*August 29, 2015*

**pre-calculus**

1) if it is really 4x = 3 then x = 3/4 a vertical line 2) 9y - 7 - 3y = 0 6 y = 7 y = 7/6 a horizontal line of slope 0 3) 7 x + 2 y = 14 2 y - -7 x + 14 y = -(7/2) x + 7
*August 29, 2015*

**integral calculus**

hmmm, graph that first function. sin a cos b = (1/2)sin(a+b)+(1/2) sin(a-b) (remember about beat frequencies :) so (1/2)[ sin(5x) dx - sin(x) dx ] ok? ======================================= let y = 3x then dy = 3 dx or dx = (1/3) dy so (5/3) [ cos^2 y dy ]
*August 29, 2015*

**Science**

agree
*August 29, 2015*

**Physics**

m = F/a
*August 29, 2015*

**Physics**

2*3600 seconds/h = 7200 seconds 75 * 7200 = 540,000 Joules total electricity use .7 * 540,000 = heat Joules .3 * 540,000 = light Joules
*August 29, 2015*

**Math**

x y = 15876 y = 9 x so 9 x^2 = 15876 x^2 = 1764 x = 42 =================== 169 + x^2 = 794 x^2 = 625 x = 25
*August 29, 2015*

**Chemistry**

150.01 - 104.70 = 45.31 grams of syrup .140 pint = 66.2 mL true so density = 45.31 grams/66.2 mL = 0.684 grams/mL = 0.684 grams/cubic centimeter
*August 29, 2015*

**physics**

work done on metal = m g h = .411*9.81*5.22 = 21.05 Joules 21.05 = .344 ke of hammer so ke of hammer = 61.2 Joulesd (1/2) 8.46 v^2 = 61.2 v^2 = 14.5 v = 3.80 m/s
*August 29, 2015*

**physics**

find bullet momentum from conservation of momentum .05 v = .55 * 4 = 2.2 then 2 V + 2.2 = 0 V = -2.2/2
*August 28, 2015*

**physics**

1.5*10^-4 = (1/2) (2.4*10^-4) v^2 so v^2 = 3/2.4 = 1.25 v = 1.11 m/s
*August 28, 2015*

**physics**

at takeoff Ke = (1/2) m v^2 = 1.5*10^-4 solve that for v work done = force * distance 1.5*10^-4 = .42 * distance
*August 28, 2015*

**physics**

change in potential energy = m g h the gravitation force is opposite to the direction of motion so work done = -m g h the escalator force is in the direction of motion so work done by it is +m g h
*August 28, 2015*

**physics**

Q = flow rate = speed * area 43 pi R^2 = n * .066 pi r^2
*August 28, 2015*

**physics**

delta p = rho g delta h 35*10^3 = 1025 *9.81 * h h = 3.48 meters
*August 28, 2015*

**physics**

hey, I did the one about the eardrums.
*August 28, 2015*

**physics**

k x = 250 = 510 x so x = 250/510
*August 28, 2015*

**physics**

power = work/time = F * d /t so 50.2 = F * 1.17 / 1.84 = 78.9 N agree
*August 28, 2015*

**Physics**

v = a t
*August 28, 2015*