Saturday

December 20, 2014

December 20, 2014

Total # Posts: 19,963

**physics**

Force * time = change of momentum = 125 * 33 often called impulse Why on earth would a baseball player push on a baseball for 33 seconds? Is that a typo?
*December 13, 2014*

**math**

4 5 or 6 p(passed) = .6 p(failed) = .4 Binomial distribution for example for 4 of 6 passed C(6,4) .6^4 .4^2 C(6,4) = 6!/[ 4!(2!)] = 6*5/2 = 15 15 * .6^4*.4^2 = .311 do that also for 6,5 and for 6,6 and add those three results
*December 13, 2014*

**math**

I am going to assume that you mean [ (n^2-4)/(n^2-2n) ] * n/(n^2+10n+16 ) Immediately you can see that n = 0 and n = 2 are excluded from the domain, also if n^2+10 n + 16 = 0 which is if n = -2 or -8 now [(n-2)(n+2)/n(n-2)] *n /[(n+2)(n+8)] = 1/(n+8)
*December 13, 2014*

**precalculus**

if a denominator is zero, you have a vertical asymptote (look at 14 as x becomes 2) if the function becomes constant you have a horizontal. look at 14 as x gets big positive and as x gets big negative
*December 13, 2014*

**math**

14 1/3 = (14*3+1)/3 = 43/3 and 43/3 = 86/6 so 86 sixths
*December 13, 2014*

**History**

agree
*December 13, 2014*

**Algebra**

1 , x^2 , 9 x^2 - 1 = d -x^2 + 9 = d --------------- 0 + 8 = 2 d d = 4 so 1 , 5 , 9 x = sqrt(5)
*December 13, 2014*

**Geometry**

Remember anything with a pointy top and straight sides has volume of base area times height times (1/3) V = (1/3) pi r^2 h
*December 13, 2014*

**math**

10 h >/= 55 so h >/= 5.5 the top one, assuming she runs an average speed for the week :)
*December 13, 2014*

**Algebra**

a , a+d, a+2d ..... a+(n-1)d or an = a +(n-1)d a5 = a + 4 (1) = 11 so a = 7 7 * 8 = 64-8 :)
*December 13, 2014*

**algebra**

It is certainly off. Perhaps it means -16 t^2 + zero initial speed up + 34 feet high but it is impossible to be certain. Good luck. The only thing you can be sure of there is -16 t^2
*December 13, 2014*

**typo**

no way On earth in the ancient feet, inches, slugs, seconds system h = Hi + Vi t - 16 t^2 please get it right so someone can answer
*December 13, 2014*

**math**

Google says 5.6 lb/gal = oz/gal yields 5.6 lb/gal = 89.6 oz/gal which is what happens if you have 16 oz/ lb 16 *5.6 = 89.6
*December 13, 2014*

**statistics**

I suppose you would use the mean but a mean of 3.8 with a standard deviation of 17.4 is pretty strange. in general this is handy: http://davidmlane.com/hyperstat/z_table.html
*December 13, 2014*

**Physics**

distance = speed time time so wavelength = speed of sound * period T but f = 1/T so wavelength = speed of sound / f f = speed /wavelength look up speed of sound at 20 C in your book (different tables available)
*December 13, 2014*

**Geography**

Oh, thanks, I thought she maybe meant the waterfall looked like Abraham Lincoln with a full moon and therefore did not reply.
*December 13, 2014*

**Reiny or Steve can you help ?**

I can not.
*December 13, 2014*

**Algebra**

n</= 2t+3 ??? is that not any n equal to or greater than -3
*December 13, 2014*

**Physics**

You are welcome.
*December 13, 2014*

**Physics**

.05 m on a side volume = .05^3 = 125 * 10^-6 m^3 mass of water displaced = 10^3 kg/m^3 * 125*10^-6 m^3 = .125 kg Archimedes says force up = weight of water displaced g = 10 m/s^2 so m g = 1.25 Newtons
*December 13, 2014*

**scholarship 7th std**

try dividing 56324 by 12 then 54324 and get 4527 exact so 4
*December 13, 2014*

**algebra 2**

4 x^2 + 4 x - 15 = 0 x = [ -4 +/- sqrt(256) ]/8 = [ -4 +/- 16] / 8 =12/8 or 20/8 = 3/2 or -5/2 or (2x-3)(2x+5) = 0
*December 13, 2014*

**Algebra**

|a-b| = 20 - |b-c|-|c-a| If b>c and c>a |a-b| = 20 - b + c - c + a =20+(a-b) if a>b then a-b = 20 + a-b and a-b = 0 if a < b then b-a = 20 -b+a 2b-2a = 20 |a-b| = 10 try others but I think you will find 10
*December 13, 2014*

**science**

anything that is different at one end like F or A
*December 13, 2014*

**math**

+i +j +k +1 -2 -1 +3 -1 +1 ================== cross product (-3)i + (-4)j + (+5)k so yes V = -3 i - 4 j + 5 k opposite to that is also parallel +3 i + 4 j -5 k add any old point to that and it is still parallel
*December 13, 2014*

**Science**

Hey, really, in one sentence? This might help: https://www.caymanchem.com/app/template/chemAssistant,Tool.vm/itemid/4001
*December 13, 2014*

**math**

geometric series a + a r + a r^2 + a r^3 ... a r^10 a =19,000 r = 1.04 S = a (1-r^n)/(1-r)
*December 13, 2014*

**no idea**

I do not know what your question is? do you want the variation sigma^2 of that data set or something?
*December 13, 2014*

**Algebra 1**

It is always negative or 0 it is a straight line with slope of -1 It is -4 when x = 0 it is 0 when x = 4
*December 13, 2014*

**statistics**

http://davidmlane.com/hyperstat/z_table.html
*December 13, 2014*

**art**

Make an educated guess. I am sure you will be correct. http://www.pbs.org/faithandreason/gengloss/enlight-body.html
*December 12, 2014*

**algebra**

complete the square to find the vertex if you do not know calculus 16 t^2 -32 t -48 = -h t^2 - 2 t - 3 = -h/16 t^2 - 2 t = -h/16 + 3 t^2 - 2 t + 1 = -h/16 + 4 = -1/16(h-64) (t-1)^2 = -(1/16) (h-64) max height is vertex at t = 1 second and h = 64 ft c) t^2 - 2 t - 3 = 0 (t-3)(t...
*December 12, 2014*

**physics 1**

Yes, but be sure to use distances in meters not cm (1.61 meters apart)
*December 12, 2014*

**Physics**

Use conservation of momentum to get initial speed of bullet/block system (m+M)V = m v so V =mv/(m+M) calculate (1/2) (m+M) V^2 then (m+M) g h = (1/2) (m+M)V^2 calculate V then go back to v = (m+M)V/m
*December 12, 2014*

**Math**

You are looking for the sum of the series? r (not d usually, that is for arithmetic) = 3 not 1/3 a = 1/27 1/27 * 3 = 1/9 1/9 * 3 = 1/3 etc then for sum of first n terms a(1-r^n)/( 1-r ) If so, yes that is for the first n terms but watch out. If you want the sum for an infinite...
*December 12, 2014*

**Math**

sister has 2 n yes boy has arithmetic sequence a1 = 2 d = 2 an = a1 + (n-1) d = 2 + (n-1)2 or an = 2n sum from n = 1 to n = n S = (n/2)(a1+an) = (n/2 )(2 + 2n) S = n + n^2 you got twice as many somehow
*December 12, 2014*

**correction**

The formulas are for the END of the year so do it for 14 years, then add that 15th deposit of 3150 (tricky wording)
*December 12, 2014*

**Math Check!!**

You get e^rt for EACH deposit for its time t 3150 [ e^14(.04) + e^13(.04) + ....e^.04] I am sorry I do not know an easy way to do that
*December 12, 2014*

**Math Check!!**

sorry, no. Your formulas are for ONE deposit at the start, not for annual deposits. Look up "amount of a sinking fund" S = 3150[ 1.04^n - 1 ] /.04
*December 12, 2014*

**calculous (check)**

By the way, on earth I think it travels 16, not 13 feet with no air resistance in the first second and d = 32, not 26 but perhaps your book is on another planet.
*December 12, 2014*

**calculous (check)**

in general an = a 1 + (n-1) d so I think f(n) = 13 + (n-1)26 that is how far it falls DURING second number n now I bet F(n) is the total distance fallen which should approximate d = 16 t^2 if we are talking feet and seconds and g = 32 ft/s^2 that is the sum of our sequence ...
*December 12, 2014*

**Math**

3937.44
*December 12, 2014*

**physics**

Glad that is settled :)
*December 12, 2014*

**magic**

How on earth would I know what this problem is asking for? Is the floor tilted? Is someone pushing? Is there a spring involved somewhere with constant k Newtons/meter ?
*December 12, 2014*

**Algebra**

by the way I would call 1994 x = 0 1996 x = 2, 1998 x = 4 , 2000 x = 6, 2001 x = 7, 2004 x = 10 then add 1994 to t at the end.
*December 12, 2014*

**Algebra**

http://www.xuru.org/rt/pr.asp you need fifth degree a x^5 + b x^4 etc to go through all the six points but can use fourth all right and get a least square fit.
*December 12, 2014*

**physics**

y component = -185 x component = -60 speed = sqrt(185^2 + 60^2) tan angle south of west = 185/60 angle south of west = 72 72+180 = 252 in math convention counterclockwise from +x axis 270-72 = 198 in navigation convention clockwise from north (about SSW)
*December 12, 2014*

**algebra parenthess needed**

(5/3) x or 5x/3 ??????? or maybe you mean 5 /(3x+3)
*December 12, 2014*

**science**

water to ice
*December 12, 2014*

**science**

air is about 80% Nitrogen and 20% Oxygen both of which are matter. guess again 3) volume is correct 4) is correct although actually chemical bonds are electrical in the end.
*December 12, 2014*

**algebra**

3 v + (1/2) y = 40 half is half, not twice
*December 12, 2014*

**Science**

seems to be pretty ductile.
*December 12, 2014*

**math**

18 = 3*3*2 15 = 3*5 LCM = 3*3*2*5 = 90 minutes so 1:30
*December 12, 2014*

**Math**

juice + bottle = 2.00 or j + b = 2.00 j - b = 1.50 ===============subtract 0 + 2 b = .50 b = .25
*December 12, 2014*

**Chemistry**

55+ 273 = 328 K He = 4 g/mol so we have 10 moles P1V1/(n1 T1) = P2V2/(n2 T2) 22.4/273 = 1.05 V2/(10*328) V2 = 269 dm^3 side of cube = 6.48 dm = 64.8 cm or 0.648 m
*December 12, 2014*

**Chemistry**

at STP 1 mol is 22.4 liters n = P V/R T 1 = 1*22.4 /R(273) R = 22.4/273 Now our problem 1 = 1 * 18.2 *273/ (22.4)K K = 222 222-273 = - 51 deg C
*December 12, 2014*

**Algebra**

or y = (11/4) x - 8
*December 12, 2014*

**Algebra**

y = (9/7) x + 1
*December 12, 2014*

**Algebra**

9 x - 7 y = -7
*December 12, 2014*

**Algebra**

Only if you really mean y = (9/7) x + 1 or in other words y = 9x/7 + 1
*December 12, 2014*

**algebra**

or y = (1/3) x -2
*December 12, 2014*

**math**

well, lets do it all in inches first 42 in + 2.5 ft (12 in/ft) + 1.5 yds(36 in/yd) = 42 + 30 + 54 = 126 inches 126 in (1 ft/12 in) = 10.5 feet 10.5 ft (1 yd/3 ft) = 3.5 yards
*December 12, 2014*

**Physics/Calc**

If in feet it is math not physics so here g = 32 ft/s^2 v = Vi + a t a = -32 so 140 = 20 - 32 t t = 3.75 seconds h = Hi + Vi t - 16 t^2 0 = Hi + 20 (3.75) - 16 (3.75)^2 solve for Hi
*December 12, 2014*

**algebra**

4*5 or 2*10 or 1*20 so 9 or 12 or 21
*December 12, 2014*

**math**

100 (.64/7.2)
*December 12, 2014*

**Physics/Calc**

been there, done that
*December 12, 2014*

**mystery question**

Without parentheses to tell me what is exponent and what is times what I do not have the slightest idea.
*December 11, 2014*

**rates and unit rates**

You are welcome.
*December 11, 2014*

**rates and unit rates**

a) four times three minutes b) 6 times a divided by 60 with any remainder being minutes for example 72 minutes /60 minutes/hr = 1 12/60 hours or 1 hour and 12 minutes
*December 11, 2014*

**Algebra 2**

e^(2n-2) = 1.47 2n-2 = ln 1.47 = .3857 2n = 2.3857 n = 1.19
*December 11, 2014*

**Algebra 2**

3.4 e^(2-2n) = 5 or what?
*December 11, 2014*

**Algebra**

How much do they have? 2 + 1 3/4 = 3 3/4 = 15/4 each gets (15/4)/3 = 5/4 James put in 2/(15/4) of the total =8/15 Karen put in (7/4)/(15/4) = 7/15 of total James (8/15) * $ 2 = $ 1.07 Karen (7/15) * $ 2 = $ 0.93
*December 11, 2014*

**science**

huh ? (1/2) m v^2 = (1/2)(0.150)(2500) Joules
*December 11, 2014*

**sheba universty collage**

x = 0 1 read n if n = -1, go to 2 if n > x then x = n go up to 1 2 print x end
*December 11, 2014*

**Mathematics - Mystery**

please elaborate
*December 11, 2014*

**Physics**

(1/2)(60) v^2 = 12,000 Joules v = 20 meters/second 20 *3.6 = 8.2 km/h
*December 11, 2014*

**math**

You are welcome.
*December 11, 2014*

**math**

7 pi (4^2) = h pi (3^2) 7 *16 = 9 h h = 7 (16/9)
*December 11, 2014*

**math**

That does not make any sense to me.
*December 11, 2014*

**math**

5/6 - 4/6 = 1/6 1/6 + what = 2 (1/4) twice because average of two things is sum over two 1/6 + what = 2/4 = 3/6 what = 2/6 = 1/3
*December 11, 2014*

**calculus**

v = dx/dt = 6 t^2 - 18 t + 12 a = dv/dt = d^2x/dt^2 = 12 t - 18 a is 0 when t = 18/12 = 3/2 = 1.5 seconds then v = 6(2.25) - 18(1.5) + 12
*December 11, 2014*

**Physic**

There is no new force on the center of mass of the system so it keeps accelerating downward at 9.8 m/s^2 so do the second part first. h = 2000 - 60(10) - 4.9(100) First part, let m1 = 1 kg and m2 = 1 kg before p = (m1+m2)60 = 120 kg m/s after p = m1 V1 + m2 V2 = V1 + 80 p ...
*December 11, 2014*

**science: question**

in general autoclaving is indeed heating
*December 11, 2014*

**Calculus**

0 </= t </= 9 dx/dt = v = 1 sin (pi t/4) Now I suspect a typo and you mean for 0 </= t </= 9 when is v positive ? from t = 0 to pi t/4 = pi or t = 0 to t = 4 v is + from t = 4 to t = 8 v is negative from t = 8 to t = 9 we are starting the next cycle and t is ...
*December 11, 2014*

**6TH GRADE MATH**

I can not very well draw a number line with my keyboard but start at ten move right 2 because -5x has to be bigger than ten by 2 we are at -5 x = 12 if - 5x = 12 then 5x = -12 so go left to -12 now x is one fifth of that -12 or -12/5 which is a bit to the left of -2
*December 11, 2014*

**math**

296/8
*December 10, 2014*

**Algebra**

256 = (1/2)(32) t^2 because 32 ft/s^2 is g in obsolete units which no one but math teachers remember.
*December 10, 2014*

**Physics >.<**

momentum before = 5000*15 + 500*0 momentum after = 5000*9 + 500*V they are the same (Newton #1) so 5000*15 = 5000*9 + 500 V
*December 10, 2014*

**Physical Science**

sure, thermal is good
*December 10, 2014*

**Physical Science**

You put lots of windows on the South side to heat up a massive wall or water tank inside the windows. That is called passive heating system. Solar energy is electromagnetic radiation. It must be converted to heat energy for example by being absorbed by a black sheet of paper ...
*December 10, 2014*

**Physics**

which one floats?
*December 10, 2014*

**Pysical Science**

Well, yes, radiation flows through empty space, the others do not which is why a vacuum bottle works but not perfectly :)
*December 10, 2014*

**typos**

which is it? why 2 equal signs? if you mean y = -2 x^2 - 6 x + 10 then complete the square -2 x^2 -6 x = y - 10 x^2 + 3x = -y/2 + 5 x^2 + 3 x + 9/4 = -y/2 +5 + 9/4 (x+3/2)^2 = -(1/2) (y -29/2) vertex at x = -3/2 and y = 29/2
*December 10, 2014*

**ratios**

1.2 (band posters) = (movie posters) 1.2 b = 24 b = 24/1.2 = 240/12 = 20
*December 10, 2014*

**physics**

a negative acceleration in classical mechanics. It can mean other things in other areas of physics.
*December 10, 2014*

**physics**

a = F/m a = 405/175 vf = a t where vf is final speed at .245 meters and t is acceleration time average speed = vf/2 .245 = average speed * t .245 = ( vf/2) t so vf t =.49 but vf = a t so a t^2 = .49 (same as d = (1/2) a t^2 ) solve for t then Vf = a t
*December 10, 2014*

**Calculus**

You are welcome.
*December 10, 2014*

**AP calc bc**

h^2 + x^2 = 625 at t = 0 x=20so h = 15 2 h dh + 2 x dx = 0 dh = -(x/h) dx dh/dt = -(20/15 ) dx/dt = -(20/15).18
*December 10, 2014*

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