Thursday

August 21, 2014

August 21, 2014

Total # Posts: 17,967

**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*

**physics**

Because the air we live in also has pressure no pressure change in a horizontal hose with no flow through it.
*March 30, 2014*

**physics**

rho g h = 1000 (9.81)(30) = 2.94*10^5 add 1 atm = 1*10^5 and get total of 3.9 * 10^5
*March 30, 2014*

**CALC 2**

try similar for the rest
*March 30, 2014*

**CALC 2**

1 at start a eats 2/3 ** 1/9 *** 1/54 b eats 1/6 ** 1/36 ** 1/108 first line is geometric series 2/3 + 2/3(1/6) + (2/3)(1/6)^2 ... An = 2/3 +(1/6)^n-1 sum of that series = a/(1-r) = (2/3)/(1-1/6) = 2/3 /5/6 = 4/5
*March 30, 2014*

**Physics**

You understand that he used quite different numbers in his example, D = 2.71 diameter 24 liters instead of 25 1.1 instead of 1.4 min
*March 30, 2014*

**Physics**

I found it all right. He has a pretty convoluted way of explaining it but it is the same thing. I have no idea why he converted to cm^3 rather than to meters^3 from Liters 1000 Liters = 1 m^3 1 Liter = 1000 cm^3 1 m^3 = 1,000,000 cm^3 but it is standard to work in meters, kg ...
*March 30, 2014*

**Statistic**

You are welcome :)
*March 30, 2014*

**Statistic**

p(good) = .7 , p(fail) = .3 n = 10 crunch it out with your binomial distribution P(2) for example = C(10,2)*.7^2*.3^8 = 10!/[8!*2!] * .49 * 6.56*10^-5 = 45 * .49 * 6.56*10^-5 = .001447
*March 30, 2014*

**physics**

work done = change in Ke = (1/2) m v^2 = 500*900 Joules power = work/time = 500 * 900 / 5 = 90,000 Watts
*March 30, 2014*

**math**

2 * 3 = 3 * 2 ????? Commutative
*March 30, 2014*

**Calculus Help Please**

f(x) = f(a) + (x-a) f'(a) f(x) = x^4 df/dx = 4x^3 let a = 2 then f(a) = 2^4 = 16 f'(a) = 4*8 = 32 f(x) = 16 + (x-a)(32) x-a = - .001 so f(1.999) = 16 -.001(32) = 16 - .032 f(1.999) = 15.968 with calculator it is 15.968 also
*March 30, 2014*

**Math (check answer)**

if you mean absolute value of 7 yes it is 7
*March 30, 2014*

**Calculus Help Please!!!**

at x = 3 y = 3*3 - 9 = 0 at x = 2.4 y = 3(2.4) - 2.4^2 = 1.44 delta y = 1.44 -0 = 1.44 dy/dx = 3 - 2 x at x = 3 dy/dx = 3 - 6 = -3 if dx = -.6 dy = -3 (-.6) = 1.8
*March 30, 2014*

**Algebra**

.163 x = 47600 x = 47600/.163
*March 30, 2014*

**Math**

You are welcome :)
*March 30, 2014*

**Math C redone**

should subtract 30 (14*2+2), not 44 c) draw a Venn diagram Only in A1 = 103 - 30 = 73 Only in A2 = 992- 30= 962 Only in A3 = 10011 - 30 = 9981 shared = 3*14 + 2 = 44 sum = 11060
*March 30, 2014*

**Math**

a) just add them 11106 b) They are all in A3 so 10011 c) draw a Venn diagram Only in A1 = 103 - 44 = 59 Only in A2 = 992- 44= 948 Only in A3 = 10011 - 44 = 9967 shared = 3*14 + 2 = 44 sum = 11018
*March 30, 2014*

**Math**

do you mean y = 18/(x^2-9) ???? if so dy/dx = -18 (2x)/(x^2-9)^2 0 at x = 0 In that interval the bigger |x|. the more negative the function so it is max when x = 0 18/-9 = -2 so C
*March 30, 2014*

**math**

You are welcome, good luck.
*March 30, 2014*

**math**

25 * .65 = 16.25 25 * 0.65 * 0.2 = 3.25 but I do not believe that 0.2. I think you have the loss 80% when it should be like 20%
*March 30, 2014*

**math**

the cooking loss is 80% ??? that does not sound right but if you are serious then 25 * (1-.35) (.2)= 25*.65*.2 = 3.25 pounds
*March 30, 2014*

**Algebra**

x^2 + (2x+20)^2 = (2x+22)^2 x^2+ 4 x^2 + 80 x + 400 = 4 x^2+88x + 484 x^2 - 8 x - 84 = 0 (x-14)(x+6) = 0 x = 14 2x+20 = 48 2x+22 = 50
*March 30, 2014*

**physic**

Plus charges flow to one side, minus charges to the other.
*March 30, 2014*

**Calculus Help Please!!!**

Oh, I see f(x) = ln (1+x) df/dx = 1/(1+x) d^2f/dx^2 = -1/(1+x)^2 f(x) = f(0) + [1/(1+0)] x - x^2/2! ... f(x) = 0 + x - x^2/2 + ..... well at a first cut when is x^2/2 =.1 x? x/2 = .1 x = .2
*March 30, 2014*

**Incomplete!**

Linear approximation to what function? Did you try to copy and paste? If so, that does not work here.
*March 30, 2014*

**Physic**

zero The plus charges on one side exactly balance the - charges on the other side. If you for example had more plus charges on one plate then they would attract negative charges to the opposite plate and would cause a flow across. Moreover the entire capacitor would then have ...
*March 30, 2014*

**Science**

I do not understand what the second question means? Balance the equations or what?
*March 30, 2014*

**Science**

Al is +3 here 2 Al + 2CuCl2 --> 2AlCl3 + 3Cu
*March 30, 2014*

**Math**

look for where second derivative is positive. ( x <0.75) https://www.wolframalpha.com/input/?i=second+derivative+of+-1%2F%28x-.75%29
*March 30, 2014*

**Physical Science 9**

Incomplete combustion ---> carbon particles and CO instead of CO2 That is not a good question by the way. You should know that for sure. The other things happen in: plants stomachs compost heaps and coffins not power plants
*March 30, 2014*

**Physics 112**

a) as t--> oo inductor is a short circuit, no reactance so V = i at big t * R V = (8.4)(.26) = 2.14 Volts b) at t = 0, i = 0, so all voltage across L 2.14 = L di/dt let i = 8.4 [ 1 - e^-t/tau ] given tau = .1 s i = 8.4 [ 1 - e^-10 t ] di/dt = 8.4 (10 e^-10 t) di/dt = 84 at ...
*March 30, 2014*

**Math**

1cm /50 in = 4 cm/x in x = 200 in
*March 30, 2014*

**Math**

It is not a proportion. It is a fraction. divide 144 by 1200 get .12 to convert a fraction to a percent, multiply by 100 100 * .12 = 12 %
*March 30, 2014*

**Math**

12/8 = 3/2 = boys/girls boys/total = 3/5 girls/total = 2/5 so that boys/girls = 3/2 so girls /total = 2/5 = girls/400 girls = 800/5 = 160
*March 30, 2014*

**Physics**

You are welcome :) Good luck. Come back and tell me when you find out.
*March 30, 2014*

**Physics**

I know the flow rate is the speed times the area. That is my field :)
*March 30, 2014*

**Physics**

I can not find an error. I hope one of the other math/physics teachers finds something.
*March 30, 2014*

**Physics**

call 41.18 41.2 maybe, sometimes they fuss about their round off rules.
*March 30, 2014*

**Physics**

Well, it is their word against mine I guess, but check my arithmetic and units carefully Physics - Damon, Sunday, March 30, 2014 at 7:21pm 25 L = 25 * 10^-3 m^3 2.77 cm = .0277 m 1.4 min = 84 seconds flow rate * time = amount pi r^2 v * 84 = .025 m^3 pi (.0139)^2 v = .025 v = ...
*March 30, 2014*

**Steve, Reiny ??**

I did this twice and do not see errors. Did I make some stupid mistake?
*March 30, 2014*

**Physics**

Well, figure out what I did wrong. (I think nothing)
*March 30, 2014*

**This is getting tiresome**

I answered this. Also the other one about circumferences several times.
*March 30, 2014*

**Math**

1/2 if a length dimension on the big one is twice the same length dimension on the little one then lengths on the small one are 1/2 those on the big one.
*March 30, 2014*

**Math**

4 * 50
*March 30, 2014*

**Math**

4 n - 6 = 2 n + 4 2 n = 10 n =5
*March 30, 2014*

**math**

22.5 quarts = .75 (total) total = 22.5/.75 we have .25 * total so we have .25 * 22.5/.75 =22.5/3 = 7.5
*March 30, 2014*

**Physics**

25 L = 25 * 10^-3 m^3 2.77 cm = .0277 m 1.4 min = 84 seconds flow rate * time = amount pi r^2 v * 84 = .025 m^3 pi (.0139)^2 v = .025 v = 41.18 m/s if 1/3 diameter then 1/9 of area so speed is nine times original 371 m/s
*March 30, 2014*

**Physic**

http://www.jiskha.com/display.cgi?id=1396215852
*March 30, 2014*

**Physic**

I did my best earlier.
*March 30, 2014*

**Calculus Help Please!!!**

LOL - Guess which of us is the mathematician and which is the Engineer :)
*March 30, 2014*

**Calculus Help Please!!!**

Q = incoming flow rate = .1 m^3/min dh/ dt = Q A where A = surface area = length * width at 20 cm depth which depth is (1/2) height width = 30 + 1/2(70-30) = 30+20 = 50 cm = .5 m wide water surface so A = 5 * .50 =2.5 m^3 so finally dh/dt = .1 * 2.5 = .25 m/min = 25 cm/min
*March 30, 2014*

**Physics**

vertical ? I thought table was level. I will assume you mean from the y axis. final momentum y component = m (5) cos 28 + m (4) cos 32 = 7.81 m final momentum x component (I will assume one + and the other -) = m (5) sin 28 - m(4) sin 32 = 2.18 m Now I will have to assume ...
*March 30, 2014*

**Physics**

inelastic, energy was radiated in sound waves
*March 30, 2014*

**Physics**

If Vector A + Vector B = Vector C then orthogonal components of the vectors also add. If V = A + B then Vx = Ax + Bx and Vy = Ay + By and Vz = Az + Bz and as many more dimensions as our tensor occupies ") (b) NO !!!!! It is only conserved in an elastic collision Energy is...
*March 30, 2014*

**algreba**

In both cases just add the two equations
*March 30, 2014*

**My typo**

" Libel is viewed differently in United Staes and Japanese law and is far more difficult to establish in a United States court. "
*March 30, 2014*

**Proofreading..Jrn Law**

Should it not say in an introductory sentence that you are talking about libel? Such as: " Libel is viewed differently in United Staes and Japanese law and is far more difficult to establish in a Japanese court. " win THE case or HIS OR HER case (singular or say &...
*March 30, 2014*

**physic**

Use the same argument but same voltage on each
*March 30, 2014*

**physic**

In series the charge has to be the same on both, call it Q by definition each capacitance C= Q/V so Veach = Q/C now in series the voltages on each capacitor add so V total = 2 Q/C but by definition our equivalent capacitance = Q/Vtotal = C/2
*March 30, 2014*

**whoops**

Use Steve's answer
*March 30, 2014*

**math**

makes good 2 miles per day after 12 day/night cycles is at the 24 mile mark so he will just make it at dusk on the 25 th day
*March 30, 2014*

**physics**

BUT they want miles/ hr so 29.4 m/s * 1 mile/1609 m * 3600 s/h = 65.8 miles/hour
*March 30, 2014*

**physics**

the ground is 3 seconds down d = (1/2) (9.81) (3)^2 correct d = 44.1 METERS (THAT IS PART B) (that is 9.81 m/s^2 * 9 s^2 so just m or meters) NOW THE SPEED (Part A) v = g t v = 9.81 m/s^2 * 3 s = 29.4 m/s (THAT IS PART A)
*March 30, 2014*

**physics**

You are terrribly fouled up with units. Give me a minute
*March 30, 2014*

**physics**

WORK IN METRIC convert later if dealing with carpenters.
*March 30, 2014*

**physics**

come on now, use what we have done v = g t but to go from m/s to mi/hr use 3600 seconds / hour and 1609 meters/mile a floor is about 3 meters
*March 30, 2014*

**Math**

2 = 1.0275^n log 2 = n log 1.0275 n = 25.6 years
*March 30, 2014*

**statistics**

Binomial distribution find probability of zero boys P(0) answer is 1 - P(0) n = 6 p = .5 and 1-p = .5 P(0) = C(6,0) (.5)^0 (.5^6) coef for any n,0 = 1 so P(0) = .5^6 = .0156 1-P(0) = .984
*March 30, 2014*

**Math 110 UOP**

Multiply 28x72 using lattice method. been there done that, see below and please post once HUH, 5^2 = 4^2 +3^2 if that is what you mean
*March 30, 2014*

**Math 110**

278 = 2*139 139 is a prime number to that is the end ***** 2 ***** 8 **** 1->2 1/4 **** 5/6 ** 7 9->0 0/4 **** 1/6 ** 2 11->1 *** 6 so 2016
*March 30, 2014*

**physics**

What speed does the ball in the first question have in falling 3.5 s? ------------------- I told you in the first line, 34.3 m/s ------------------- in 4 sec d = .5 * 9.81 *16 = 78.5 meters so no
*March 30, 2014*

**physics**

v = g t = 9.81 * 3.5 = 34.3 m/s but what if it hit the ground? d = (1/2) g t^2 = 60 meters so it has not hit ground yet, whew
*March 30, 2014*

**Physics**

area = A = pi D^2/4 = pi (.0277^2)/4 = 6.03*10^-4 m^2 Q = volume/second 25 * 10^-3 m^3 / 84 s = .298 *10^-3 m^3/s A v = Q v = Q/A = .298*10^-3/6.03*10^-4 = .0494 *10^1 = .494 m/s
*March 30, 2014*

**physics**

a = change in velocity/change in time = 44/5 = 8.8 ft/s^2 a = same formula = (88-44)/4 = 11 ft/s^2 a = (66 -88)/3 = -7.33 ft/s^2 sum of a*t / total t (8.8*5 + 11*4 - 7.33*3)/12 = 5.5 m/s^2
*March 30, 2014*

**physics**

5/20=4 km/min = 4,000 m/min = 66.67 m/s? BECAUSE 5/20 = 1/4 not 4
*March 30, 2014*

**physics**

5000 meters in 20*60 = 1200 seconds Vi = 30,000 m / 3600 s = 83.3 m/s v = Vi + a t 0 = 83.3 + a (1200) a = - .0694 = - 6.94 * 10^-2 m/s^2 average velocity with constant acceleration = (first + last)/2 = 83.3/2 = 41.7 m/s
*March 30, 2014*

**physics**

750 m/ 20 s 1500 m / 45 s
*March 30, 2014*

**college algebra**

2 x 10to the what? and 3.5 times ten to the what ?
*March 30, 2014*

**US government**

Well, presidents seem to start wars without much voting in Congress these days :)
*March 30, 2014*

**US government**

Well, I guess our first choices are consistent :)
*March 30, 2014*

**US government**

the government the citizens among many other possible answers such as: money, health military, poor capital , labor federal government , states
*March 30, 2014*

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