Saturday

January 21, 2017
Total # Posts: 28,805

**Calculus**

This is a closed path check first if field is potential in which case integral is zero F = z^2 i + 2xy j + 3y^2k del cross F = 0 ???? nope no way so first line = 3 i + 0 j + 0 k F dot line = Fx *3 = 0*3 = 0 second line in x from 3 to 3 = 0 in y from 0 to 3 = 3 in z from 0 to 1...

*November 23, 2016*

**Calc**

or rather curl F

*November 23, 2016*

**but still think MITx**

:)

*November 23, 2016*

**Calc**

curve is ellipse at z = 11 and 5, y = 0 and x = +/-3 (-3 , 0 , 11) (+3 , 0, 5) at z = 8 , x = 0 and y = +/-3 The normal to that ellipse is in he x z plane and is perpendicular to the line joining(-3, 0 ,11)and (3,0,5) slope of that original line dz/dx = -6/6 = -1 remarkable so...

*November 23, 2016*

**MITx**

Just asking :)

*November 23, 2016*

**Calc**

You doing an MITx subject?

*November 23, 2016*

**Calc**

curl of F over the surface curl is i j k d/dx d/dy d/dz fx fy fz is =(dFz/dy-dFy/dz)i +(dFx/dz-dFz/dx)j +(dFy/dx-dFx/dy)k here Curl F =(ex-9x)i +(y-ey)j +(9z-z)k

*November 23, 2016*

**Calc**

Flux = int over S of F dot [1i - (dz/dx)^2j -(dz/dy)^2k] F dot [i -4x^2 j - 4y^2 k] [xy - 4x^2yz -4y^2xz]dx dy now put in 2 -x^2-y^2 for z and do the integrals from 0 to 1

*November 23, 2016*

**physics**

if boy at 1 meter girl at (4/3) meter

*November 23, 2016*

**physics**

50 N * .2 m = 10 Nm

*November 23, 2016*

**The Graphical Method**

I get 40 of A, 0 of B for profit = 1000 maximize 25 x + 15 y constraints 5x+4y<=300 2x+3y<=108 x>=0 y>=0 x+y>=1 (phony to fill fields)

*November 23, 2016*

**linear programming**

http://www.wolframalpha.com/widget/widgetPopup.jsp?p=v&id=1e692c6f72587b2cbd3e7be018fd8960&title=Linear%20Programming%20Calculator&theme=blue try that while I look at your problem

*November 23, 2016*

**Algebra 2 (Please help Ms. Sue!)**

292 ?

*November 23, 2016*

**Algebra 2 (Please help Ms. Sue!)**

f(x)/(x-a) = f(a) here a = -3 so we need f(-3) f(-3) =(-3)^4-9(-3)^3-5(-3)^2-3(-3)+4 = 81 + 9*27 - 45 +9 + 4 = 81 + 243 - 45 + 9 + 4

*November 23, 2016*

**Linear Programming**

note, to make the program format happy I put in max 180x+60y x+y</=60 20x+10y<=700 x>=0 y>=0 x+y>=1 phony but fills boxes

*November 23, 2016*

**Linear Programming**

a+b<=60 20 a + 10b </= 700 a and b >=0 maximize 180 a + 60 b intersections at 0,60 35,0 10,50 at a = 0, b = 60 180 (0) + 60 *60 = 3600 at a = 10, b = 50 180(10) + 60(50) = 4800 at a = 35, b = 0 180(35) = 6300 so plant 35 acres of a and zero of b. Use the whole $700 ...

*November 23, 2016*

**Linear Programming**

http://www.wolframalpha.com/widget/widgetPopup.jsp?p=v&id=1e692c6f72587b2cbd3e7be018fd8960&title=Linear%20Programming%20Calculator&theme=blue

*November 23, 2016*

**Gaussian Elimination Method**

+5 -4 12 divide by 5 to get 1 -5 +3 +9 +1 -4/5 12/5 multiply by 5 and add -5 +3.0 +9 +1 -4/5 12/5 +0 -1.0 21 multiply by -1 +1 -4/5 12/5 +0 +1.0 -21 so y = -21 now multiply second eqn by 4/5 and add to first +1 -4/5 12/5 +0 +4/5 -84/5 +1 +0 -72/5 +0 +1 -21 x = -72/5, y = -21

*November 23, 2016*

**Physics**

sure, if you use a seesaw, you must be twice as far from the pivot point as the weight is. You must move twice as far down as the weight moves up. (draw geometry) You could use a pulley with one end of the line attached to the ceiling, then running down through the block on ...

*November 23, 2016*

**Calculus**

depth = h dV/dh = area of surface (draw it :) dV/dh = pi r^2 = surface area r = (2.7/4.3)h remember to use chain rule. for example dV/dt = 59.5 m^3/min but dV/dt = dV/dh dh/dt so dh/dt = 59.5/ (pi r^2) etc

*November 23, 2016*

**Science**

Now what American mammal is marsupial?

*November 23, 2016*

**Science**

eg: http://www.ucmp.berkeley.edu/mammal/marsupial/marsupial.html

*November 23, 2016*

**Science**

google kangaroo, marsupial :)

*November 23, 2016*

**help me plz**

I wish I knew what rt{t} meant but anyway we will need to do r of 9 and delta r for delta t at t = 9 r = t i + t^1.5 j + e^.25 t k dr/dt= i + 1.5 t^.5 j + .5 e^.25 t so dr (your delta r) = dt i + 1.5 t^.5 dt + .25 e^.25 t dt j Then r(9)= 9 i + 27 j+ 9.49 k dr = dt i + 4.5 dt j...

*November 23, 2016*

**calculus**

The DOMAIN is all real t HOWEVER the RANGE is only from -1 to +1 in i and -4 to + 4 in j and all real numbers in k

*November 23, 2016*

**science**

Senpai - buying books instead of borrowing from the library uses up trees (as well as a lot of other stuff like fuel).

*November 22, 2016*

**science**

Which do you think Jaden? Think of the effect of each answer on trash heaps and energy supplies and forests.

*November 22, 2016*

**Science**

initial momentum = 1 kg * 7 m/s - 2 kg * 7/6 m/s = = 14/3 kg m/s final momentum is the same 14/3 = 1 * V1 + 2 * V2 so V1 = 14/3 - 2 V2 initial Ke = (1/2)(1)(49) + (1/2)(2)(49/36) final Ke = .75*initial Ke = (1/2)(1)V1^2 + (1/2)(2)V2^2

*November 22, 2016*

**PHYSICS PLEASE HELP ME**

force of gravity down slope = m g sin 30 = .5 m g force of friction up slope = FF use FF to get angular acceleration FF r = I alpha so alpha = FF r/I = FF r/(2/5 mr^2) alpha = 5FF/2mr FF = 2 m r alpha/5 a = r alpha so alpha = a/r and F = m a so m a = .5 m g - FF m a = .5 m g...

*November 22, 2016*

**math**

I do not know what your triangle looks like area outside triangle = circle area pi r^2 - triangle area

*November 22, 2016*

**maths**

volume of sphere = (4/3)pi r^3 pi R^2 h = (4/3) pi r^2 h = (4/3) r^2/R^2

*November 22, 2016*

**maths**

just like your other problem, your turn

*November 22, 2016*

**Physics- Equilibrium**

If I had to pick one it would be c. Constant velocity means no acceleration which means no net force.

*November 21, 2016*

**Physocs- Components of Resultant Vectors**

A = 5 i - 3 j B = 5 i + 4 j --------------- C = 10i + 1 j

*November 21, 2016*

**Physics- Accleration of a Falling Penny**

google terminal velocity

*November 21, 2016*

**Physics**

Sorry for the long explanation. I am a naval architect and this subject is close to me :)

*November 21, 2016*

**Physics**

It is true if the body is floating. The force upward from the water is equal to the weight of the water displaced. If the body is floating, that water weight must be equal to the weight of the body and the body rises in the water until that is true. That is how ships float. If...

*November 21, 2016*

**Physics- Baseball thrown upwards, accleration**

THE ENTIRE TIME the acceleration is one g, about 9.8 m/s^2 downward. In other words yes, b

*November 21, 2016*

**Statistics**

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

*November 21, 2016*

**Physics-Tension Force**

infinite

*November 21, 2016*

**Physics**

.4 N up 9.8*.145 down m a = .4 - 9.8*.145 that is about .4 - 1.4 or -1 a = -1/.145 = about -7 a

*November 21, 2016*

**Science**

I replied .

*November 21, 2016*

**Math**

9 3/4 = 39/4 39/4 / 3/4 = 39/4 * 4/3 = 39/3 = 13

*November 21, 2016*

**TIP MATH!**

well Ms Sue used the fact that 15% is halfway between 10% and 20% I used a tenth plus half of a tenth. same difference :)

*November 21, 2016*

**TIP MATH!**

10% + 5% = 15% 2.3 + half of that 2.3 + 1.2 = 3.50 ps the accurate answer is 3.49

*November 21, 2016*

**Maths help asap please.**

n (n+1) + n+1 n^2 + n + n + 1 n^2 + 2n + 1 = (n+1)(n+1)

*November 21, 2016*

**Physics**

d = speed * time d = (100 km/60 min) * 5 min d = 25/3

*November 21, 2016*

**Science plsss help!**

4) I suspect is B 5) .5^6 = .0156 = 1.6 % agree second number 5, really that fast?

*November 21, 2016*

**Physics**

one of those two speeds is negative

*November 21, 2016*

**math**

sin ? = 1/1.25 tan ? = sin ?/cos ? = 1/v

*November 20, 2016*

**physics**

sqrt (100 + 16) = sqrt 116 = srt (4*29) = 2 sqrt(29) tan angle above x axis = 4/10 |a| = (1/.5) *2 sqrt 29 = 4 sqrt 29 at same tan^-1(.4)

*November 20, 2016*

**calculus antiderivation**

Vi = 60 mi/h * 5280 ft/mi /3600 s/h Vf = 45 * 5280/3600 Vf = Vi - 11 t solve for t =========================== 0 = Vi - 11 T T = Vi/11 d = Vi T - 5.5 T^2

*November 20, 2016*

**Math**

1.5/6 = x/16 x = 16 * 1.5 / 6

*November 20, 2016*

**Maths trigonometry**

tan 30 = 150/x

*November 20, 2016*

**factor of 2**

for part b .5 m g (d+x) = .5 k (x)^2 + .5 m v^2 we know d from part a m v^2 = m g d + m g x - k x^2 m v dv/dx = m g - k x dv/dx = 0 at max v k x = m g

*November 19, 2016*

**Physics**

You are welcome.

*November 19, 2016*

**Physics**

Not that easy m g (d+.23) sin 30 = .5 k (.23)^2 sin 30 = .5 so m g (d+.23)= k (.23)^2 3.2 (9.8)(d+.23) = 443 * .23^2 =========================== for part b m g (d+x) = k (x)^2 + .5 m v^2 we know d from part a .5 m v^2 = m g d + m g x - k x^2 m v dv/dx = m g - 2 k x dv/dx = 0 ...

*November 19, 2016*

**Physics**

Slides (d + .23) total m g (d+.23) sin 30 = .5 k (.23)^2

*November 19, 2016*

**math - business**

The y intercept is where x = 0 so -12,000 is correct The x axis intercepts are when y, the profit, = 0 that is when x = 2 and z = 15 correct the 15 is from 6000 - 400 x = 0 x = 60/4 x = 15

*November 19, 2016*

**Math Help**

probability of no boys = .5^5 so probability of one or more than 1 = 1 - .5^5 = .969

*November 19, 2016*

**calc**

so displacement is zero and distance is 5.33 + 15.75 + 10.42 = 31.5 check my arithmetic !!!!

*November 19, 2016*

**calc REPAIR of displacement**

v = t^3 - 10 t^2 + 27 t - 18 integral = t^4/4-10t^3/3 +27t^2/2 -18t at 7 integral = -7.58 at 1 integral = -7.58 so displacement = 0

*November 19, 2016*

**calc**

I used this to do the numbers: http://www.mathportal.org/calculators/calculus/integral-calculator.php t = 1 to t = 3 int = +5.33 t = 3 to t = 6 int = -15.75 t = 6 to t = 7 int = +10.42 so distance = -21.5 this also says my answer for part 1 should have been 5.33 -15.75+10.42...

*November 19, 2016*

**calc**

(t-1)(t-3)(t-6) = 0 so 1 to 3 then 3 to 6 then 6 to 7

*November 19, 2016*

**calc**

integrate to find x(1) and x(7) x(7)-x(1) is the displacement vector to find the distance scalar we must know when the particle is moving forward and when back and integrate over those intervals adding absolute values v = t^3 - 10 t^2 + 27 t - 18 integral = t^4/4-10t^3/3 +27t^...

*November 19, 2016*

**Calc**

integral of (500-3t) = 500 t - 1.5 t^2 at t = 13, integral = 500(13)-1.5(169) = 6500 - 253.5 = 6246.5 liters

*November 19, 2016*

**Math**

integer

*November 18, 2016*

**Math**

Are you sure you mean sqrt(-9) ??? That is an imaginary number. Maybe you mean sqrt (25-9) = sqrt (16) which is 4 which is a whole number and an integer

*November 18, 2016*

**Math**

5 + sqrt -9 5 + 3 sqt(-1) 5 + 3 i complex

*November 18, 2016*

**math**

m < 13 n > 13 p < 5 I think you mean at most 35 people 20 + a <= 35 a <= 15 so no more than 15

*November 18, 2016*

**watch units!**

watch out, km/hour given

*November 18, 2016*

**Calc**

a = (V2-V1)/(t2-t1) V2 = 90,000/3600 = 25 m/s V1 = 25,000/3600 = 6.94 t2-t1 = 13 so a = 1.39 m/s^2 ====================== d = V1 t + (1/2)a t^2 = 6.94 *13 + .695*169 = 208 m

*November 18, 2016*

**Science**

sounds right to me

*November 18, 2016*

**Math**

using same web site for normal dist A = .1 M = 72 sd = 9 .1 area is anything below 60.46 If I try bottom .3, anything below a C, I get A = .3 ---> below 67.28, that is the boundary for the HIGHEST D

*November 18, 2016*

**Math**

http://davidmlane.com/hyperstat/z_table.html area = .4 mean = 72 SD = 9 .4 are between 71.5 and 72.5 so 71.5

*November 18, 2016*

**physics**

total drop = 2.2+ .55 = 2.75 m drop in gravity Potential energy = = 6.95 * 9.81 * 2.75 = increase in spring Pe = (1/2)k x^2 = .5 *k * .55^2 so k = (6.95*9.81*2.75)/(.5*.55*.55)

*November 18, 2016*

**math algebra**

cold 1/8 tub/min hot 1/12 tub/min drain -1/7 tub/min so sum 1/8 +1/12 - 1/7 tub/min = 3/24 + 2/24 - 1/7 = 5/24 - 1/7 = 35/168 - 24/168 = 11/168 tubs/min = 168/11 min/tub = 15.3 min

*November 18, 2016*

**Math**

false say 1 by 1 1*1 = 1 cm^2 but 1.1 * 1.1 = 1.21 cm^2 .21 is more than .1 :)

*November 18, 2016*

**physics**

Ke = (1/2)m v^2 = Pe = (1/2)k x^2 (1/2)m (2v)^2 = (1/2)k (nx)^2 v^2 multiplied by 4 so x^2 multiplied by 4 so 2 times original x

*November 18, 2016*

**Math**

mean win = (1+2+3+0+0+0) = 6/6 = $1 so lose .25 per toss so lose $25 for 100 games

*November 18, 2016*

**PRE-CALCULUS**

a) 150,000 * 1.054^20 = 320,440.07 check do the others the same way as I showed you in the previous problem below

*November 18, 2016*

**PRE-CALCULUS**

r = .12/n where n = times per year a = 5000 * (1+r)^8n eg annual: 5000 * 1.12^8 semi where n = 2 5000 * 1.06^16 quarterly where n = 4 5000 *1.03^32 etc continuous a = 5000 e^.12 t = 5000 e^.96 = 13058.48

*November 18, 2016*

**Math**

3*18 = 54 m^2

*November 17, 2016*

**Math**

b/g = 7/9 g-12 = b so (g-12)/g = 7/9 9(g-12) = 7g 2 g = 108 g = 54 b = 42 sum = 96

*November 17, 2016*

**Science**

on the other hand if he carried it 500 m UP, then 100 * 500 = 50,000 Joules The problem does not say direction so who knows?

*November 17, 2016*

**MATH HELP!!**

Starlight Tree Farm sells Douglas firs and Noble firs. One December they sold 139 more Douglas firs than Noble firs. The total number of trees sold was 377. Which equation could be used to solve for n, the number of Noble fir trees sold

*November 17, 2016*

**MATH HELP!!**

You are welome

*November 17, 2016*

**MATH HELP!!**

25 6/25 - 20/25 = -14/25

*November 17, 2016*

**math**

100 times the fraction

*November 17, 2016*

**US History**

I guess maybe because Fort Neccessity is near Pittsburgh?

*November 17, 2016*

**Calculus**

delta x = .1 x range ____ y at right 1.0 to 1.1 ____ 2/1.1 = 1.82 times .1 = .182 1.1 to 1.2 ____ 2/1.2 = 1.67 times .1 = .167 1.2 to 1.3 etc in the end add them up .182 + .167 etc

*November 17, 2016*

**US History**

I do not think slaves were in Rhode Island before about 1700 so I agree with you. Pilgrims landed in Plymouth MA in 1620 and settlement of RI was thus later than that. I have my doubts about timing in SC as well.

*November 17, 2016*

**physics typo?**

Vi = 47 m/s d = 50 =============== v = Vi + a t 0 = 47 + a t a t = -47 or a = -47/t =============== d = Vi t + .5 a t^2 50 = 47 t + .5 a t^2 50 = 47 t +.5(-47/t)t^2 50 = 47 t - .5*47 t 50 = .5*47 t t = 100/47 then a = -47/(100/47)= -22 m/s^2 > twice gravity I think maybe ...

*November 17, 2016*

**Math**

13 = .65 x x = 13/.65 = 20

*November 17, 2016*

**Math**

(1/3)/5 = 1/15 but 5/(1/3) = 15

*November 17, 2016*

**US History**

The Spanish certainly DID find gold. They became the most powerful country in Europe for a while due to their riches from the New World. So I agree with you.

*November 17, 2016*

**Math algebra**

I have a hunch you mean f(x)= (x-2)/(x^2-81) which is (x-2)/ [ (x-9)(x+9) ] it is zero if the numerator is zero so when x = 2 it is undefined when the denominator is zero x = 9 or x = -9

*November 17, 2016*

**Math algebra**

AVA + .2*10^9 = 2 * AVE T + .6*10^9 = AVA AVA + AVE + T = 6.5*10^9 ============================ do them all in billions well T = AVA - .6 AVE = .5 AVA + .2 so AVA + .5 AVA + .2 + AVA - .6 = 6.5 2.5 AVA = 6.9 take it from there

*November 17, 2016*

**Math algebra**

(20+2x)(30+2x) = 936 600 + 100 x + 4 x^2 = 936 4 x^2 + 100 x - 336 = 0 x^2 + 25 x - 84 = 0 (x - 3 )(x + 28) = 0 x = 3 feet

*November 17, 2016*

**ANOTHER TRIANGLE MATH PROB!**

Get it?

*November 17, 2016*