Saturday

April 19, 2014

April 19, 2014

Total # Posts: 16,178

**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

**math**

You are welcome, good luck.

**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%

**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

**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

**physic**

Plus charges flow to one side, minus charges to the other.

**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

**Incomplete!**

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

**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 ...

**Science**

I do not understand what the second question means? Balance the equations or what?

**Science**

Al is +3 here 2 Al + 2CuCl2 --> 2AlCl3 + 3Cu

**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

**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

**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 ...

**Math**

1cm /50 in = 4 cm/x in x = 200 in

**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 %

**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

**Physics**

You are welcome :) Good luck. Come back and tell me when you find out.

**Physics**

I know the flow rate is the speed times the area. That is my field :)

**Physics**

I can not find an error. I hope one of the other math/physics teachers finds something.

**Physics**

call 41.18 41.2 maybe, sometimes they fuss about their round off rules.

**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 = ...

**Steve, Reiny ??**

I did this twice and do not see errors. Did I make some stupid mistake?

**Physics**

Well, figure out what I did wrong. (I think nothing)

**This is getting tiresome**

I answered this. Also the other one about circumferences several times.

**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.

**Math**

4 * 50

**Math**

4 n - 6 = 2 n + 4 2 n = 10 n =5

**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

**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

**Physic**

http://www.jiskha.com/display.cgi?id=1396215852

**Physic**

I did my best earlier.

**Calculus Help Please!!!**

LOL - Guess which of us is the mathematician and which is the Engineer :)

**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

**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 some...

**Physics**

inelastic, energy was radiated in sound waves

**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...

**algreba**

In both cases just add the two equations

**My typo**

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

**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 &quo...

**physic**

Use the same argument but same voltage on each

**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

**whoops**

Use Steve's answer

**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

**physics**

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

**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)

**physics**

You are terrribly fouled up with units. Give me a minute

**physics**

WORK IN METRIC convert later if dealing with carpenters.

**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

**Math**

2 = 1.0275^n log 2 = n log 1.0275 n = 25.6 years

**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

**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

**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

**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

**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

**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

**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

**physics**

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

**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

**physics**

750 m/ 20 s 1500 m / 45 s

**college algebra**

2 x 10to the what? and 3.5 times ten to the what ?

**US government**

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

**US government**

Well, I guess our first choices are consistent :)

**US government**

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

**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

**math**

Yes, I wondered about this state's educational achievements as well :)

**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

**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

**calcules**

change in percent bought is only half the percent change in price

**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

**probability**

Steve answered this above.

**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.

**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, ...

**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

**no figure**

You can not copy and paste here so I can not see the geometry.

**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...

**Physic Moment of inertia**

I = (2/5) m r^2 = (2/5)(11.1)(.630) = 2.8 kg m^2

**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

**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...

**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

**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.

**Stats**

http://davidmlane.com/hyperstat/z_table.html

**Stats**

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

**math**

1000 * .90 * .90 = ?

**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...

**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

**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...

**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...

**Science (check please)**

Good, you are welcome :)

**Science (check please)**

agree

**Math/precalc**

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

**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

**Pre calc**

Oh, sorry, tangent repeats every pi, not 2 pi so period is 2 pi, not 4 pi

**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

**math**

You are welcome:)

**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 ...

**Physics**

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

**Math**

4 x + 9 = 65 subtract 9 from both sides 4 x = 56 divide both sides by 4 x = 14

**math**

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

**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)

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