# Posts by Damon

Total # Posts: 29,622

**physics**

ub^2 = .25 ua^2 average speed for initial slowing = .5(ua+ub) assume constant a t = .05/.5(ua+ub) = .1/(ua+ub) v = Vi +at ub = ua + a t ub-ua = a (.1)/(ua+ub) .1 a = -(ua^2-ub^2) .1 a = - (.75 ua^2) a = -7.5ua^2 now complete trip 0 = ua + a t t = ua/7.5ua^2 = 1/(7.5ua) d = Vi...

*November 24, 2016*

**Math**

There are lots of different ways. perhaps the easiest to understand uses the distributive property 12 = 10 + 2 13 = 10 + 3 (10 + 2) (10 + 3) = 10 (10+3) + 2 (10+3) = 100 + 30 + 20 + 6 = 100 + 50 + 6 = 156 ========================== You can shorten that by saying 10(13) + 2(13...

*November 24, 2016*

**Physics**

If there is no moment (torque) then there is no change of angular momentum [ I omega = constant] If they are not opposite in direction through the same point, they cause a moment, called a "couple"

*November 24, 2016*

**algebra**

n and 2 n 2 n - n = 20 n = 20 and so answer = 2n = 40

*November 23, 2016*

**Gaussian Elimination Method**

LOL, forgot the old easy stuff :)

*November 23, 2016*

**Gaussian Elimination Method**

to check, put it back in -4(-1) -(-2) = ? yes 6 12(-1) -2(-2) = ? yes -8

*November 23, 2016*

**physics**

m v^2/r horizontal m g down tan theta = mg/(mv^2/R)where theta is angle down from horizontal but cos theta = .7/2.8 so theta = 75.5 deg so tan theta = 3.87 so 3.87 = mg/mv^2/R = 9.81/(v^2/.7) v = 1.33 m/s m v^2/R = .4*1.77/.7 = 1.01 m g = .4*9.81 = 3.92 T^2 = 1.01^2 +3.92^2 T...

*November 23, 2016*

**Math**

9*10^-3 LY (5.88*10^12 mi/LY) = 52.92 * 10^9 mi = 5.292 * 10^10 mi

*November 23, 2016*

**math!**

q = first questions/min 2 q = final que/min t min for first ten 48 - t min for final 11 q t = 10 so t = 10/q q t + 2q(48-t) = 21 10 + 96q - 20 = 21 96 q = 31 q = 31/96 questions/min so twice that = 62/96 to finish ======================== check t = 960/31 = 30.97 min 48-t = 17...

*November 23, 2016*

**Algebra 2**

.75 x + .42 y = .5784 (100) x+y = 100 ============================ .75 x + .42 y = 57.84 .75 x + .75 y = 75 ---------------------- -.33 y = - 17.16 y = 52 x = 48 E

*November 23, 2016*

**Physics**

h f = 14.7 eV lambda = c T = c/f c about 3*10^8 m/s

*November 23, 2016*

**Physiscs**

well the length is L sqrt 13 but who cares? force up from floor = m g = 3g (because wall is smooth none up there) force sideways from wall = F thus force sideways at floor = F toward wall Now moments about center clockwise mg * 2L/2 = m g L counter clockwise F*1.5 L + F*1.5 L...

*November 23, 2016*

**physics**

80 km/hr * 1 hr/3600s * 1000 m/km = 22.2 m/s tan T = v^2/r / g = v^2/gr tan T = 22.2^2/(981) tan T = .502 T = 26 deg 39 min

*November 23, 2016*

**Physics**

rho g h 1000 * 9.81 * 20 = 196,200 Pascals = 1.94 atm gage (over 1 atm) or 2.94 atm absolute

*November 23, 2016*

**Physics**

done already

*November 23, 2016*

**Calculus**

Oh, but I said where x = +/- infinity

*November 23, 2016*

**Calculus**

Oh, yes :)O

*November 23, 2016*

**Calculus**

Oh my, look around x = 0 and x = 1 and x = infinity and x = -infinity http://www.wolframalpha.com/input/?i=plot+1%2F(x(x-1))

*November 23, 2016*

**Math**

a) sin is + in I and II b) cos is - in II so there only c) hard to sketch here from origin up 7 distance 25 x^2 + 7^2 =625 and x is - x^2 = 625 - 49 = 576 x = -24 so point is at (-24,7) cos C = -24/25 tan C = -7/24

*November 23, 2016*

**Math**

cos /sin = -1 = cotan 90 + 45 360 - 45

*November 23, 2016*

**Consider the linear programming problem**

You are welcome.

*November 23, 2016*

**Consider the linear programming problem**

which we could have seen without doing the problem :) The potato seed costs less and the profit is more

*November 23, 2016*

**Consider the linear programming problem**

maximize 150 x + 50 y x + y <=70 20 x + 60 y <= 3000 x>= 0 y>= 0 x+y >=1 to fill in input form only http://www.wolframalpha.com/widget/widgetPopup.jsp?p=v&id=1e692c6f72587b2cbd3e7be018fd8960&title=Linear%20Programming%20Calculator&theme=blue result 10500 at (70,0)

*November 23, 2016*

**Calculus**

f' = 10 - 10/x^2 f" = 0 - 10 [ -2/x^3] = 20/x^3 I do not see anyplace where the curvature passes through zero except at x = +/- infinity

*November 23, 2016*

**Linear Programming to Maximize Profit**

You are welcome.

*November 23, 2016*

**Linear Programming to Maximize Profit**

Oh my heavens I have done so many linear programming problems tonight! s uses 6 plastic d uses 3 plastic so 6 s + 3 d </= 300 s uses 4 metal d uses 8 metal so 4 s + 8 d </= 608 s </=22 maximize 10 s + 2 d I get 332 at (22,56) using http://www.wolframalpha.com/widget/...

*November 23, 2016*

**math**

7x = 1.40 x = .20 2x = 0.40 4x = 0.80 5x = 1.00 7x = 1.40 sum = $3.60

*November 23, 2016*

**simplex method**

For instructions using Simplex with pivots etc see http://en.wikipedia.org/wiki/Simplex_algorithm

*November 23, 2016*

**doing with linear programming**

http://www.wolframalpha.com/widget/widgetPopup.jsp?p=v&id=1e692c6f72587b2cbd3e7be018fd8960&title=Linear%20Programming%20Calculator&theme=blue max = 3220 at (12,50)

*November 23, 2016*

**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*