Monday

September 1, 2014

September 1, 2014

Total # Posts: 18,200

**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*

**Math**

a = .5 r = .5 a r^(n-1) = .5 * .5(6) = .0078125 That is maybe a pepper corn :) http://www.mathsisfun.com/algebra/sequences-sums-geometric.html
*March 30, 2014*

**math**

Yes, I wondered about this state's educational achievements as well :)
*March 30, 2014*

**math**

.56 (11) = 6.16 I have no idea what the standard deviation is so can not do more. If I knew it I would use mean of 6.16 and some standard deviation in: http://davidmlane.com/hyperstat/z_table.html
*March 30, 2014*

**Physics**

The force from the car on the truck = 4420 - 1230 a So our task is to find a total m = 1230 + 2180 = 3410 kg total F = 4420 - 750 = 3670 N so a = 3670/3410 = 1.08 m/s^2 so finally F on truck = 4420 - 1230 (1.08) F on truck = 3096 Newtons
*March 30, 2014*

**calcules**

change in percent bought is only half the percent change in price
*March 30, 2014*

**calcules**

Q = 342.5 / P^.5314 dQ/dP = -342.5 (.5314) P^-.4686/ P^1.063 so dQ/dP = - 182 P^-1.5316 well, we need to know what P is at the intersection P = q P^1.5314 = 342.5 1.5314 log P = 2.535 log P = 1.655 P = 45.2 so dQ/dP at intersection = -182(45.2)^-1.5316 = .531
*March 30, 2014*

**probability**

Steve answered this above.
*March 29, 2014*

**physics**

The electric company is supplying energy to the room and it is heating up. We hope she is using a CFL or LED lamp to minimize heating of the room and waste of energy.
*March 29, 2014*

**3 science questions**

7. Which of the following is used to make biomass fuel? B. plants and animal waste C. coal <----- ============================ NO !!!!!!!!!! plants and animal waste!! bio mass means made out of present biological materials, not dinosaurs. ----------------------- 11. Solar, ...
*March 29, 2014*

**physic**

change in rpm = 170 170 rev/min *1 min/60 s * 2 pi radians/rev = 17.8 radians/second change which is delta omega alpha = change in omega/ change in time -17.8 radians/second / 4.4 seconds = 4.05 radians/second^2
*March 29, 2014*

**no figure**

You can not copy and paste here so I can not see the geometry.
*March 29, 2014*

**Physic Angular momentum and torque**

r = 0.19 m I =.5 m r^2 =.5 (1)(.19)^2 = .0181 kg m^2 1700 rev/min * 1 min/60 s * 2 pi rad/rev = 178 radians/second = omega L =I * omega .0181 * 178 = 3.22 kg m^2/s final omega = initial omega - alpha t alpha (4.6) = -178 alpha = - 38.7 radians/s^2 Torque = I alpha = -.0181 (38...
*March 29, 2014*

**Physic Moment of inertia**

I = (2/5) m r^2 = (2/5)(11.1)(.630) = 2.8 kg m^2
*March 29, 2014*

**Help!! Physics**

c = speed of light = 3 * 10^8 m/s 199 = c T T =199/3*10^8 f = 1/T = 300* 10^6/199 = 1.51 * 10^6 Hz omega = 2 pi f = 9.47 * 10^6 omega^2 = 1/(LC) = 89.7*10^12 so C (785 * 10^-6) = (1/89.7) 10^-12 C = (1/70414) 10^-6 = 1.42 * 10^-5*10^-6 = 1.42 * 10-11
*March 29, 2014*

**algebra**

It represents the average speed during that interval or in other words the distance traveled during that interval/ 3 seconds d(5) = 16 * 25 = 400 d(2) = 16*4 = 64 distance during those three seconds = 400-64 = 336 feet 336 ft/3 s = 112 ft/s = average speed for that interval By...
*March 29, 2014*

**Stats**

easy to say they do not happen 1-pA = .6 1-pB = .5 so probability that neither happens is .3 so probability that at least one happens is 1-.3 = .7
*March 29, 2014*

**maths natural log**

Huh ? as t--> oo e^-anything t ----> 1/ e^big ---->0 so W ---> 0 and b ---> 800 What happened was that the black increased form their initial 50 to their final 800 while destroying the white populations, typical invasive species.
*March 29, 2014*

**Stats**

http://davidmlane.com/hyperstat/z_table.html
*March 29, 2014*

**Stats**

I can not see your graph. You can not copy and paste here, but find the area in that region
*March 29, 2014*

**math**

1000 * .90 * .90 = ?
*March 29, 2014*

**Calculus**

the rate of change of volume is the surface area times the rate of change of height 450 ft^3/min = surface area * dh/dt surface area = pi r^2 450 = pi (30^2) dh/dt dh/dt = .159 ft/min You could do this by saying V = pi r^2 h dV/dh = pi r^2 dV/dh*dh/dt = pi r^2 dh/dt chain rule...
*March 28, 2014*

**math**

you mean how many zeros I think look at b^2-4ac 49 -16*8 is NEGATIVE so two complex conjugate solutions, NO real solutions
*March 28, 2014*

**math**

find the zeros of that parabola, use the + one (I turned the parabola upside down because I like positive x^2 term) .06 x^2 - 9.6 x - 5.4 = 0 use x = [-b +/- sqrt(b^2-4ac) ]/2a while I use wolfram alpha http://www.wolframalpha.com/input/?i=+.06+x^2+-+9.6+x+-+5.4+%3D+0++ to get...
*March 28, 2014*

**Physics**

A) we pushed back on the snow Therefore Prof. Newton says (Law #3) that the snow pushes forward on us B) 410 forward - 187 backward = 223 N forward C) F = m a 223 = 530 (the driver evidently has no mass:) * a so a = 223/530 = .421 m/s^2 D) v = Vi + a t v = 0 + .421 (7.3) v = 3...
*March 28, 2014*

**Science (check please)**

Good, you are welcome :)
*March 28, 2014*

**Science (check please)**

agree
*March 28, 2014*

**Math/precalc**

Sorry tangent period is pi, not 2 pi so (2/3) x = 1 pi x = 3 pi/2 = period
*March 28, 2014*

**Math/precalc**

I do not think amplitude means much for a tangent function which goes to infinity twice a period so I would not say 3 but maybe undefined. when the x term increases to 2 pi from 0 we have gone a period so (2/3) x = 2 pi x = 3 pi when we have gone a period period = 3 pi
*March 28, 2014*

**Pre calc**

Oh, sorry, tangent repeats every pi, not 2 pi so period is 2 pi, not 4 pi
*March 28, 2014*

**Pre calc**

argument of tan = (x/2 + pi/8) when x = 0 right now argument of tan = (pi/8) what will x be when this is bigger by two pi? (x/2 + pi/8) = (2 pi + pi/8) or x/2 = 2 pi x = 4 pi = period or how much x has to increase to go a whole way around 2 pi radians
*March 28, 2014*

**math**

You are welcome:)
*March 28, 2014*

**math**

assume no calculus allowed thus complete he square to find the vertex of this parabola 16 t^2 - 20 t - 2 = -h 16 t^2 -20 t = - h + 2 t^2 - 5/4 t = - h/16 + 1/8 t^2- 5/4 t+ 25/64 = -h/16 + 8/64 + 25/64 (t - 5/8)^2 = -(1/16)(h - 33/4) so in 5/8 of a second it reaches the vertex ...
*March 28, 2014*

**Physics**

clockwise moments about support (ignoring g which cancels) (50 - 27) m - 27(.31) = 0 23 m = 8.37 m = 0.364
*March 28, 2014*

**Math**

4 x + 9 = 65 subtract 9 from both sides 4 x = 56 divide both sides by 4 x = 14
*March 28, 2014*

**math**

180 lbs/2.5 days = 72 lbs/day 72 lbs / day * 30 days = 2160 lbs about one ton, two half ton pickups full
*March 28, 2014*

**math**

It was in a steel box lined with layers and layers of bubble wrap ( one of the many ways my students use in the contest)
*March 28, 2014*

**Calculus**

so it is positive for x>.316 and for x <.316
*March 28, 2014*

**Calculus**

Note that you did the second derivative correctly. It is easier to write it their way y" = 10e^(-5x^2)(10x^2-1) It is zero at x = +/- .316
*March 28, 2014*

**Calculus**

first http://www.wolframalpha.com/input/?i=plot++e^%28-5x^2%29 Then this for second derivative and graph https://www.wolframalpha.com/input/?i=second+derivative+of+e^%28-5x^2%29
*March 28, 2014*

**Calculus**

first http://www.wolframalpha.com/input/?i=plot++e^%28-5x^2%29
*March 28, 2014*

**Spanish needs Sra**

Well, all I can say is I understand you and can follow the directions just fine, but I am no Spanish grammar expert so hope one comes along.
*March 28, 2014*

**physics**

mass 1 accelerates downward at a so mass 2 accelerates up at a tension = T mass 1: m g - T = m a so 3 g - T = 3 a mass 2: T - mg = m a so T = 2 (g+a) substitute T in mass 1 equation 3 g - 2(g+a) = 3 a g - 2 a = 3 a a = g/5 = 9.81/5 = 1.962 You could also use the total mass of ...
*March 28, 2014*

**science (check please (:)**

Wow, glad you chose the right answer :)
*March 28, 2014*

**science (check please (:)**

DO NOT USE BOTTLED WATER !!! 1. It is a waste of money 2. It fills the ocean with plastic bottle remains. That is once it gets thrown off the boats and bridges. 3. It burns up energy and resources for manufacture of bottles, distribution fuel etc etc anyway your answer is right.
*March 28, 2014*

**science (check)**

You are correct, but did you have to ask? :)
*March 28, 2014*

**math help**

for 5 days 2/5 + 1/5 + 3/5 = 6/5*5 = 30/5 Sat 3 *4/5 = 12/5 Wed -2/5 for wet Pepper 30/5 + 12/5 - 2/5 = 40/5 = 8 hours
*March 28, 2014*

**math**

http://www.jiskha.com/display.cgi?id=1396046268
*March 28, 2014*

**science (check)**

Yes, but the individuals may be fish or whatever.
*March 28, 2014*

**Math for grade 6 peace**

96 = 0.48 x x = 96/0.48
*March 28, 2014*

**Physics**

Take moment about the left end total mass = 20 + 14 + 39 = 73 kg That is force up from pivot (I am going to do force in kilograms because g will cancel everywhere.) pivot distance from left = 1.4 Distance left to 39 kg = x (our L is (x -1.4) ) moments about left end 14 * 0 - ...
*March 28, 2014*

**science**

distance = speed * time same time, higher speed --> bigger distance
*March 27, 2014*

**Math**

x + 15 + 2x + 27 = 180 3 x = 138 x = 46
*March 27, 2014*

**math help!!**

[ (x^2+5x) - 6 ] [(x^2+5x) + 6 ] (x^2 + 5 x - 6) (x^2 + 5x + 6) now if the back of your book says (x^2 + 5 x + 6)( x^2 + 5 x - 6) That is the SAME
*March 27, 2014*

**math help!!**

You got the second one, just reversed x y = y x !
*March 27, 2014*

**geometry**

width of alley = 60 tan 40 so second building = 60 + 60 tan^2 40 =60 (1 + tan^2 40) = 110 ft
*March 27, 2014*

**geometry**

ratio of ANY lengths in similar figures is the same 12/16 = 3/4 2. Ratios of ANY areas is length ratio squared 9/16 3. 54 * 16/9 = 96
*March 27, 2014*

**math help**

That is exactly what we got x y = y x the order is just reversed
*March 27, 2014*

**math help**

LOL, no need for wolfram !
*March 27, 2014*

**math help**

remember - -d = + d
*March 27, 2014*

**math help**

[ (a-b) - (c-d) ] - [ (a-b) + (c-d) ] [ a - b - c + d ] [ a - b + c - d ]
*March 27, 2014*

**Calculus Help Please!!!**

One of us made an arithmetic mistake. It is up to Tanya to get it right :)
*March 27, 2014*

**Calculus Help Please!!!**

rate of change of temp proportional to temp above room temp which is 20 to make it easy on the arithmetic define T' = real T - 20 dT'/dt = k (T') dT/T' = k dt ln T' = k t T' = C e^kt let's call t = 0 at 1:30 T = 32.5 so T' = 12.5 12.5 = C e^0 = ...
*March 27, 2014*

**Calculus Help Please!!!**

I am going to assume it is algebra first take t = 0 at 1:30 T = Ti - k t Ti = 32.5 so T = 32.5 - k t 30.3 = 32.5 - k (1 hour) k = 2.2 so T = 32.5 - 2.2 t 37 = 32.5 - 2.2 t t = - 2.04 call it 2 hours so by that linear model 11:30 am now I will work on the more realistic ...
*March 27, 2014*

**Calculus Help Please!!!**

Are you sure this is calculus? You want exponential decay to room temp? Or is it algebra and you want a linear function?
*March 27, 2014*

**math**

Yes !!! You got it. even the -1 * -1 = + 1 part
*March 27, 2014*

**math**

sorry about the caps, was doing tax returns with caps lock on
*March 27, 2014*

**math**

yOU HAVE [X - [Y-Z) ] THAT IS [ X - Y - NEGATIVE Z ] - A NEGATIVE IS POSITIVE [ X -Y PLUS Z ]
*March 27, 2014*

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