Thursday

July 30, 2015

July 30, 2015

Total # Posts: 21,579

**physics**

(1/2) m v^2 start = m g h at top so m g h = 2 * 10^4 m = 2*10^4 / (9.81*50) = 40.8 kg
*January 6, 2015*

**Science**

Probably with carbon 14 dating. http://dwb4.unl.edu/Chem/CHEM869Z/CHEM869ZLinks/www.all.mq.edu.au/online/edu/egypt/carbdate.htm
*January 6, 2015*

**physics**

5.72*10^3 * 3.11 * 10^3 = 17.8 * 10^6 = 1.78 * 10^7 Joules
*January 6, 2015*

**Math**

30/20 = 1.5 , 90/60 = 1/5 the same 15/20 = 3/4 , 10/15 = 2/3 NOT the same
*January 6, 2015*

**Math**

I would say A
*January 6, 2015*

**Science**

You are welcome
*January 6, 2015*

**Math**

a + d(n-1) a + d (2) = 1985 a + d(7) = 2015 ----------------subtract 0 - 5 d = - 30 d = 6 a + 12 = 1985 a = 1973 1973 + 6(14) = 2057
*January 6, 2015*

**physics**

normal force down = 18.4*9.8 - 126 sin 34.1 so friction force = .123 (18.4*9.8-126 sin 34.1) work done by friction - friction force * 20 meters
*January 6, 2015*

**Science**

Yes That is all per molecule.
*January 6, 2015*

**4th grd math**

3*8 = 24 fish per day 2.5 * 8 = 16 + 4 = 20 eaten so 4 left over each day I guess you do not have seagulls where you live :)
*January 6, 2015*

**Math**

15 sandwiches /.75 hr * 3 hr = 60 sandwiches
*January 6, 2015*

**Science**

You are welcome.
*January 6, 2015*

**Science**

I mean (6/18)*10^23 atoms/gram
*January 6, 2015*

**Science**

2 hydrogens, one oxygen in a molecule so three atoms per molecule a mol is 6*10^23 molecules so 18 * 10^23 atoms per molecule a mol weighs 2+16 = 18 grams so (6/18) * 10^23 molecules per gram
*January 6, 2015*

**math**

sorry, yes
*January 6, 2015*

**math**

39 - 15 = 25 spaces so 25,000 feet 10:11- 10:05 = 6 minutes 25,000/6 = 4167 feet/min a little less than a mile a minute or 60 miles per hour
*January 6, 2015*

**math**

1/4 inch to the foot so one inch = 4 feet 6*4 = 24 feet
*January 6, 2015*

**math**

14/10 = 1.4 lions per tiger or 14/24 = 7/12 lions (not loins I assume) and 10/24 = 5/12 tigers
*January 6, 2015*

**algebra**

there will be a short time on the way up to 28 and a long one for the way down, we want the second minus the first when will h = 28 feet? 28 = 4 + 56 t -16 t^2 16 t^2 - 56 t + 24 = 0 2 t^2 - 7 t + 3 = 0 (2t-1)(t-3) = 0 t = .5 or t = 3 so t = 2.5 seconds above 28
*January 6, 2015*

**Math**

dollars / t shirts = dollars per t shirt A 40/16 = 2.50 per shirt B 140/84 = 1.67 per shirt
*January 6, 2015*

**Math**

You are welcome.
*January 6, 2015*

**Math**

7 d - 4 d - 32 = -8 3 d = 24 d = 8
*January 6, 2015*

**math**

oh, I assumed that the 23 was a typo and it meant 2/3
*January 6, 2015*

**math**

I think you added 6 girls and get 20 out of 30
*January 6, 2015*

**math**

Rodger is right
*January 6, 2015*

**math**

3/7 7+10+7 = 24 total students 14 are girls so 14/24 = 7/12 suspect you mean 2/3 are girls (14+x) /(24+x) = 2/3 42 + 3 x = 48 + 2x x = 6 more girls
*January 6, 2015*

**Math**

" it is also perpendicular line" should be it is at the intersection of two perpendicular lines.
*January 6, 2015*

**math**

I guess. There are lots of ways to do it actually.
*January 6, 2015*

**math**

6 * 5^2 = 6 * 25 = 600/4 = 150 12* 5^3 = 12 * 125 = 1500 1500 * 150 = 225,000
*January 6, 2015*

**math**

The one with a right angle.
*January 6, 2015*

**Physics**

(1/2) m v^2 = m g h so v = sqrt (2 g h) = sqrt (2*9.81*4)
*January 6, 2015*

**Math**

4 * 4.5 = 18 pineapple 8 * 4.5 = 36 orange 12 * 4.5 = 54 seltzer
*January 6, 2015*

**Math**

I mean multiply each number of cups by 4.5
*January 6, 2015*

**Math**

4+8+12 = 24 cups 108/24 = 4.5 so multiply each number of cups by 6 to get 108 cups Note, a serving is evidently not a cup because 24 cups is 18 servings. I do not know if this is an intentional confusion or a typo.
*January 6, 2015*

**Math**

I agree with you.
*January 6, 2015*

**civics**

Protect all citizens in time of trouble***
*January 6, 2015*

**civics**

I agree with you. The last.
*January 6, 2015*

**civics**

I agree, although I am tempted by the first choice :)
*January 6, 2015*

**Physics**

http://www.jiskha.com/display.cgi?id=1420573371#1420573371.1420574332
*January 6, 2015*

**Physics again?**

Just did that
*January 6, 2015*

**Physics**

I will have to assume that it goes the entire 100 meters during this deceleration and crashes into the moon at .5 m/s -.5 = -20 + a t 100 = -20 t + .5 a t^2 a = (-.5+20)/t -100 = -20 t + .5 (20-.5) t 100 = 20 t -9.75 t t = 9.75 seconds to slow down (part b) a = +2 up (part a...
*January 6, 2015*

**Civics**

You are welcome.
*January 6, 2015*

**Civics**

To ensure the powers of each branch of government are limited and checked by another branch
*January 6, 2015*

**Math**

600 - 280 = 320 100 (320/600) = 53.33
*January 6, 2015*

**Math**

time = distance/speed 5/(x/5) + 30/(5x) + 20/x = 25/x + 6/x + 20/x = 51/x she has gone 5 + 30 + 20 = 55 km b) 2 = x/5 so x = 10 and time = 51/10 = 5.1 hr c) 40 = 5x x = 8 time = 51/8 = 6.375 difference = 6.375 - 5.1 = 1.275
*January 6, 2015*

**Bosaso**

http://davidmlane.com/hyperstat/z_table.html
*January 6, 2015*

**Physics**

u = 53/2 = 26.5 m/s forever v = Vi - 9.81 t h = Vi t - 4.9 t^2 = 54 =Vi(2)-4.9(4) or 54 = 2 Vi - 19.6 so Vi = 36.8 m/s ========================== at top, v = 0 0 = 36.8 - 9.81 t t = 3.75 seconds at top but we know u = 26.5 m/s so D = u t = 26.5 * 3.75
*January 6, 2015*

**mechanics and heat**

2 v^2 = 100 v = 10/sqrt 2 = speed of 2 kg mass 4 (10/sqrt 2) = .4 V V = 100/sqrt 2 speed of small mass (1/2)(.4)(10,000/2) = 1,000 = Ke of little mass
*January 6, 2015*

**Physics**

70*5 - 5*20 = 75 v
*January 5, 2015*

**Physics**

increase of length = L *coefficient of expansion * 30
*January 5, 2015*

**Algebra**

1.35 s + 1.85 t = 1.65 * 20 s + t = 20 so s = (20-t) =========================== 1.35 (20-t) + 1.85 t = 33 solve for t, go back and get s
*January 4, 2015*

**math/compound**

40 periods at a rate of .0615/4 2500 (1.015375)^40=2500(1.841) = $4602.55
*January 3, 2015*

**physics**

since you did not specify the direction very well (41 deg from horizontal or vertical? up or down from horizontal? Up or down from vertical?) I will have to be very general in the answer. Vi = 9.66 sin or cos or -sin or -cos of 41 v = Vi - g t at top v = 0 0 = Vi -9.81 t so t...
*January 3, 2015*

**Algebra2**

g = -32 ft/s^2 in the feet (old American - English) system so (1/2)g = -16 Watch out, most of us use metric units g = -9.81 m/s^2 in which case h = Hi + Vi t - 4.9 t^2
*January 3, 2015*

**Math**

y = -3x - 4n slope = m = -3 y axis intercept, b, is y when x = 0 which is -4n
*January 1, 2015*

**Physics**

If the block moves .40 meters then the line is pulled 5 * .4 = 2 meters (a) the work done by the puller person on that line is W in = 60 N * 2 meters = 120 Joules (b) the useful work done on the block was to lift it .40 meters work out = m g h = 25 * 9.81 * .4 = 98.1 Joules so...
*January 1, 2015*

**Physics**

The basic form of Newton's second law is Force = rate of change of momentum = change of (m V) /time if m is constant this is the familiar form F = m dV/dt = m A but here it is simple to use the more fundamental form change of momentum/time = m v/t = 1 *5/5 Newtons as ...
*January 1, 2015*

**science**

strain proportional to stress
*January 1, 2015*

**science**

I am not sure where the fulcrum is but if it is in the middle then: 20 * 5 = 30 * x x = 5(2/3) = 10/3 from center which is 10/3 + 5 from the boy which is 25/3 = 8 1/3 meters from the boy
*January 1, 2015*

**physics**

R1 = 13/3 = 4.33 m R10 = 2 m T = 5 seconds / 10 waves = .5 s f = 1/T = 2 Hz wavelength = (4.33-2)/9 = .259 meter v = .259/.5 = .518 m/s
*January 1, 2015*

**physics**

Only one where the ball fires a rocket after hitting the floor :)
*January 1, 2015*

**Calculus**

You are welcome.
*December 31, 2014*

**Calculus**

f" = [(-1)(x+1)^3 - 3(1-x)(x+1)^2]/(x+1)^6 = [-(x+1)+3(x-1)]/(x+1)^4 ( I don't understand how you got this!!) Looks like division of top and bottom by (x+1)^2 and also -(1-x) = + (x-1)
*December 31, 2014*

**Algebra**

You are welcome :)
*December 31, 2014*

**Algebra**

These problems are pretty advanced for class that has not reached logarithms.
*December 31, 2014*

**Algebra**

hmmm well, you need 2^something = 1000 2^3 = 8 2^4 = 16 2^5 = 32 2^6 = 64 2^7 = 128 2^8 = 256 2^9 = 512 2^10 = about 1000 so d = about 10 so 2*10 = 20 days. It said approximate :)
*December 31, 2014*

**Algebra**

take the log to any base of both sides for example base 10 log 1000 = d log 2 d = 3/.301 = 9.96 2 day periods or 20 days check my reply to your earlier efficiency problem
*December 31, 2014*

**Algebra-Check my answer please!**

5.9 * 10^12 miles/year *2.2 * 10^6 years = 12.98 * 10^18 = 1.298 * 10^19 I get
*December 31, 2014*

**Algebra**

up to the left, and up to the right d^2 = (2-a)^2 + (1-7)^2 d^2 = 45 = 4 - 4 a + a^2 + 36 5 = a^2 - 4 a a^2 - 4 a - 5 = 0 (a-5)(a+1) = 0 a = 5 or a = -1
*December 31, 2014*

**Physics**

You are welcome.
*December 31, 2014*

**Physics**

LOL, yes, depends on purity of water etc. Those numbers are the same to me :)
*December 31, 2014*

**Physics**

water is 4186 Joules/kg deg C 110,000 kg 8 deg C so heat out into water = 4186*110,000*8 = 3.68 * 10^9 Joules into water electricity in = 150,000 * 28 * 3600 = 1.51*10^10 Joules efficiency = out/in = .368/1.51 = .244 = 24.4 %
*December 31, 2014*

**Physics**

If you understand 2, I think you can do 3 You need to look up heat capacity of water in Joules/kg deg C
*December 31, 2014*

**Physics**

2. 1 watt hr = 3600 watt seconds or Joules so 2.0 Mwh = 7200 MJ 33 MJ/kg * m in kg *.18 = 7200 MJ m = 1212 kg
*December 31, 2014*

**Physics**

electrical work in = 180,000 *120 = 21.6 *10^6 Joules mechanical work out = 10,500*9.81*218 = 22.5 *10^6 Joules magic? on moon? let's see ? 10th floor about 9 * 3 meters high or 27 meters, not 218 meters
*December 31, 2014*

**Graphing**

(2+3)/(-5-3) = (y+3) / (x-3) 5/-8 = (y+3) / (x-3) 5 x -15 = -8 y -24 5 x + 8 y = -9 5+8-9 = 4
*December 31, 2014*

**Chemistry missing data**

same amount of what ?
*December 31, 2014*

**Algebra**

(-3-7)/(5+2) = (a-7)/(3+2) -10/7 = (a-7)/5 etc
*December 31, 2014*

**Algebra**

second function, the one in the table, when x goes up 2, y goes up 4 always so y = (4/2) x + b = 2x+b when x = 1, y = 5 so 5 = 2(1) + b b = 3 so y = 2 x + 3 both of your functions are straight lines that go through (0,3) the original one has slope = 4 the second one has half ...
*December 31, 2014*

**calculus**

Good luck :)
*December 31, 2014*

**calculus**

Approximate ³√26 by using an appropriate linearization. y = x^(1/3) we know that if x = 27, y = 3 so I will start there. Of course you could do something else. dy/dx = (1/3) x^-2/3 at x = 27 dy/dx = (1/3) /9 = 1/27 = m so y = (1/27) x + b 3 = (1/27)(27) + b b = 2 so...
*December 31, 2014*

**calculus**

b should come out just like a :)
*December 31, 2014*

**calculus**

y = m x + b at (25,5) 5 = m (25) + b what is m, the slope, there? y = x^.5 dy/dx = .5 x^-.5 = .5/5 = .1 = m so 5 = .1 (25) + b 2.5 = b so our line through (25,5) is y = .1 x + 2.5 now if x = 26 y = 2.6 + 2.5 = 5.1 that is part a check it sqrt 26 = 5.099 Awful close !!! :)
*December 31, 2014*

**physics**

v = 10 t = 30 m/s = 3000 cm/s
*December 30, 2014*

**physics**

F = C coef v^2 (some area) if there is flow separation probably the cross sectional area is the important one pi r^2 if there is little flow separation then maybe surface areas 4 pi r^2. coefficients for spheres are shown both ways they may want you to say F = (6 pi)coef of ...
*December 30, 2014*

**math**

-20 x - 5 = 15 -20 x = 20 x = -1
*December 30, 2014*

**maths**

I am not sure there is much you can do but calculate the values.
*December 30, 2014*

**Algebra 2**

they are equal to 15 when m = 5 Plan A is more expensive if m>5 Plan B is more expensive for m <5 so you want m>/= 5, C
*December 29, 2014*

**Physics**

2 and 4 are correct as are others using 0.15 for initial velocity up. However I am quite sure that was not the intent because the velocity is so low it makes little sense and the shot hardly gets above the hand.
*December 29, 2014*

**Physics typo ?**

you seem to have both 15 and .15 for the velocity. Compromise at 1.5 maybe?
*December 29, 2014*

**Physics**

Let's assume the acceleration, a , is constant then the force is constant F = m a work = integral of force dx from low speed to high speed which is force * (Xend - Xbegin) because F is constant so we need to know x begin and x end let x begin be 0 then d^2x/dt^2 = a dx/dt...
*December 29, 2014*

**PRE-CALC**

2,000 e^.06 t 2,000 e^.24 2,000 * 1.27124915 $ 2,542.50
*December 29, 2014*

**Algebra 1**

3/4 = (y-6)/(x+4) take it from there
*December 29, 2014*

**Precalculus**

agree with Reiny. Note the problem here is really not the algebra but the problem of keeping significant figures when subtracting numbers that are close to each other. However, you must start by doing the algebra correctly :)
*December 29, 2014*

**Precalculus**

NOTE - Steve left a tan 33 out of 800 tan 33 http://www.jiskha.com/display.cgi?id=1419896043
*December 29, 2014*

**Precalculus**

x tan 33 = x tan 35 - 800 tan 33 I do not know how you got what you got, but I just did this problem a few minutes ago and will go find it I hope.
*December 29, 2014*

**sds chemisry**

endo --- put heat in (cure fiberglass resin with a heat lamp :) exo -- heat comes out (burn wood)
*December 29, 2014*

**Algebra 1**

In other words a V with 45 degree slopes and point at (0,1)
*December 29, 2014*

**Pre-Calculus**

LOL - I bet they were supposed to do it with a slide rule. Otherwise too easy.
*December 29, 2014*