Wednesday

July 30, 2014

July 30, 2014

Total # Posts: 17,565

**math**

4 sqrt 6 ---------- sqrt (6*5) = 4/sqrt 5 * sqrt 5/sqrt 5 = (4/5) sqrt 5

**PreCalculus**

If the events are independent, you multiply the probabilities. For example that would not apply to falling and getting eaten by the shark BECAUSE you were hit by lightning or the ship sank but only as independent events.

**physics**

2.74 + 3.19 cos 61.2

**Math**

Mike (1/60) project/min Walter (w project/min) together (1 + 60 w)/60 project /min [(1+60 w)/60 ] 40 = 1 project 1 + 60 w = 6/4 60 w = .5 w = .0083333 1/w = min/project = 120 minutes

**ALGEBRA**

L = w + 3 (L+2)(w+2) = 70 + (L)(w) (w+5)(w+2) = 70 + (w+3)(w) w^2 + 7 w + 10 = 70 + w^2 + 3 w 4 w - 60 = 0 w = 15 L = w+3 = 18

**ALGEBRA**

approach speed = v + v+60 = 2 v+60 d = rate * time = (2v+60)(5) = 10 v + 300 unfortunately we were not given d, their distance apart so I am faced with a problem or a typo.

**maths**

Republican and Tea Party ?

**Math**

(100 pages / h hours) (1 hour/60 min) = (100/60 h) pages/min * m minutes = (100 m /60 h) Probably C but if so you have a typo

**calculus 2**

y = x^(1/3) ????? h = (6-1)/10 = . x____________ y 1____________ 1 1.5 _________ 1.145 2____________ 1.260 2.5__________ 1.357 3 etc etc etc 3.5 4 4.5 5 5.5 6 integral is about (.5/3)(y0+4y1+2y2+4y3 +2y4 ......+1y10)

**Physics**

Normal force = m g cos 30 max friction force = mu m g cos 30 power in = power out P = (mu m g cos 30) v

**Physics -- check answers please**

yes yes

**Physics**

-4 F (opposite charges attract)

**pharmacy**

huh? .930/3 = 0.310 mg

**Calculus**

easy way: r = (4/16) h = (1/4) h surface area = pi r^2 = pi (1/16) h^2 dV = surface area * dh dV = pi (1/16) h^2 dh DV/dt = (1/16) pi h^2 dh/dt hard way: V = (pi/3) r^2 h given again r^2 = (1/16) h^2 V = (pi/3)(1/16) h^3 dV/dh = (pi/16) h^2 again dV/dt = (pi/16) h^2 dh/dt

**math**

speed = s current = c s + c = 17.2 s - c = 10.4 ------------ add 2 s = 27.6 etc.

**Math**

Those are both straight lines, graph them. x - 3 y= 10 goes through (0,-10/3) and (10,0) we are on that line and left of it 3 x - 2y = 5 goes through (0,-2.5 ) and (5/3 , 0) we are on that line and below it where do they hit? 3 x - 9 y = 30 3 x - 2 y = 5 ------------------ -7 ...

**Physics 2**

speed of light is about 3 * 10^8 meters/ second by the way

**physics**

diffraction grating again

**physics**

y = m lambda D/d d bigger means y smaller

**physics**

less distance ---> more friction, more retarding force

**physics**

momentum before = 2 *.28 momentm after = 2 v + .5 * 1.5 .56 = 2 v + .75 2 v = -.19 v = - .095 (The Answer :) Now by the way is this possible? initial kinetic energy = (1/2)2 (.28)^2 = .0784 Joules final Ke = (1/2)(2)(-.095)^2 + (1/2)(.5)(2.25) = .009025 + .5625 = .5715 Joules ...

**calculus 2**

odd function from -3 to + 3 ---> 0 I suspect

**Algebra**

60 = L + 2 w so L = 60 -2 w A = L w A = (60-2 w)w = 60 w - 2 w^2 If you know calculus, just take derivative and set to zero and you are done If not, complete the square to find vertex of parabola. w^2 - 30 w = -A/2 w^2 - 30 w + 225 = -A/2 + 225 (w-15)^2 = -(1/2)(A - 450) so w ...

**Physics**

When a wave travels from fast to slow medium: Reflected wave is inverted. (crest -reflected as trough is 180 deg phase shift)

**Algebra**

Sketch those lines slopes of +/- 1 center axis halfway between 1 and 5 so at y = 3 the lines cross at (2,3), so that is center of hyperbola so (x-2)^2/a^2 - (y-3)^2/b^2 = 1 slopes of asymptotes = +/- b/a so b = a (x-2)^2/a^2 - (y-3)^2/a^2 = 1 put that point in now (4-2)^2/a^2 ...

**Physics -- check answers please**

1. ok 2. We used to use a "diffraction grating" in the spectroscopy lab to get the clearest pattern.

**Calc**

Oh, sorry, I thought you meant just the length of that splitting fence.

**Calc**

.000000000000001 feet or perhaps the length of the width of a cow. :) The problem does not make much sense as stated. You could make the field extremely longs and not at all wide and divide it with a little fence in the middle the length of your very short ends.

**algebra 1**

well, do part B and you will have the answer to part A 100 - 1.9 = 98.1 percent so every time we go a meter, we multiply by .981 after x meters f(x) = 1700 * .981^x (Part B answer) which is exponential, not linear. (part A answer) It does not lose a constant "amount"...

**Calculus: Determine the constants from function**

dh/dx = 0 at critical points dh/dx = 3 x^2 + 2 b x = 0 x (3x+2b) = 0 so at (2,4), 3x+2b = 0 = 6 + 2b so b = -3 so h = x^3 -3 x^2 + d at x = 2, h = -4 -4 = 8 - 12 + d d = 0 so h = x^3 -3 x^2

**College Algebra**

^4t not to the t/4 1.01875^4t = 7200 4 t = log 7200/log 1.01875 t = 120 years

**Math 221**

That is: https://www.khanacademy.org/math/linear-algebra/vectors_and_spaces/vectors/v/linear-algebra--parametric-representations-of-lines

**Math 221**

Your talk of origins does not make a lot of sense to me since the origin is at (0,0) for all your problems. However perhaps your class is trying to work toward a vector version of this material where you specify a point and move out from there at a certain slope. In that case ...

**Math 221**

If y = x + 8 the x axis intercept for that is when y = 0 0 = x + 8 x = -8 so (-8,0) the y axis intercept for that is when x = 0 which is b in y = m x + b so 8 so at (0, 8) --------------------------------------- I thought I did that other one too. This time you did the problem...

**Math 221**

Go back, I just saw this below and replied. http://www.jiskha.com/display.cgi?id=1406309814

**MAth**

10 y^2 - 15 y + 2 y - 3 or 10 y^2 - 13 y - 3

**Physics**

I do not have your figure. HOWEVER (Note - I do not care what mass it is, call it m not 200 until part c) initial kinetic energy = (1/2)m(100) = 50 m Ke at any height h = 50 m + m g (100-h) so at any height h (Points A B and C) (1/2) m v^2 = 50 m + m g (100-h) note m cancels) ...

**math**

You are welcome.

**math**

n on shelf .5 n are #1 .25 * .5 n = .125 n are #3 .5 n + .125 n = .625 n are either #1 or #3 so 1 n-.625 n = .375 n = 5 n = 5/.375 = 13 1/3 hmmmm, I hope we have a fractional bookcase

**math**

so, like maybe they were 270 miles apart and collided at x pm :) they approach each other at 45 miles/hr 270 miles/45 miles/hr = 6 hours 6+5 = 11 pm

**science**

No, but note that they grow back after a few weeks ! http://birds.about.com/od/grooming/a/How-To-Clip-Your-Birds-Wings.htm

**Math 221**

typo yp should be y1

**Math 221**

Oh, I see what you are doing. given y = x + 4 we want parallel and through (-7,1) since y = 1 x + 4 has slope = m = 1 ANY parallel line ALSO has slope = 1 slope = 1 = (y-yp)/(x - x1) or 1 = ( y - 1 ) / (x - -7) 1 = (y-1) / (x+7) y-1 = x + 7 y = x + 8 I like my way better, but ...

**Math 221**

The origin is always at (0,0) However none of your lines go through the origin.

**Math 221**

yes I did not entirely follow all your steps though. The way I do it y = 1 x + 4 m = 1, so my new m must be 1 also if parallel ( I did not follow you here) point is (-7, 1) 1 = 1(-7) + b yes b = 8 y = x + 8

**do not understand**

I can not fathom your notation.

**Math 221**

assume you mean y = (-1/2) x + 1 slope m = -1/2 so slope of perpendicular = -1/m = 2 y = 2 x + b put in point 2 = 2(4) + b b = -6 so I agree y = 2 x - 6 You are getting these right but not the way I do them and I have not figured out what you are doing yet.

**Math 221**

I think I just did these above.

**math**

how many combinations of three from 5 n!/[ r!(n-r)! ] 5!/[2!(3!)] = 10 or do one by 1 the hard way A B - C, D, E --> 3 A C - D, E -->2 A D - E -->1 B C - D, E -->2 B D - E -->1 C D - A -->1 3+2+1+2+1+1 = 10

**Math**

I got 120

**Math**

Adults = .6 * 840 = 504 children = .4 * 840 = 336 504 = .7 (840 - boys)

**MATH**

profit = .2 S cost = 72 72 + .2 s = s 72 = .8 s s = 90 =============================== Javier had J = 28 28 + (4/5) D = 64 (4/5) D = 36 D = 45

**Math**

perimeter = 4 x so x = 15 area = 225 -------------------- A does task/r per day B does task/s per day [ 1/r + 1/s ] task/day together so 1/ [ 1/r + 1/s ] = r s / (r+s) or r s ------- r + s which is probably d) but you left the parentheses out

**statistic**

I can not see your problems. Copy and paste does not work here. However I am sure this link will do the trick anyway: http://davidmlane.com/hyperstat/z_table.html

**Math: Zeroes**

Oh, 50 factorial 50 * 49 * 48 ..... 1 3.0414093e+64 so 64 Just GOOGLE 50 factorial

**Math: Zeroes**

I would just write the list out if I could not guess :) You could shorten the task as so: 1 ----- 10 11 -----20 21 -----30 31 .....40 41 .....50 :-)> . .

**Chemistry**

you have two Mg for every one O2 so mols Mg/mols O2 = 2/1 3 mols Mg ( 1 mol O2 / 2 mols Mg) = 3/2 = 1.5 mols O2 ----- Yes 1 O2/2 MgO 3 O2 ( 2 MgO/1 O2 ) = 6 MgO

**typo**

By the way, if you happen to know Physics: v = Vi - 32 t at top v = 0 0 = 56 - 32 t t = 1.75 seconds 32 ft/sec^2 = acceleration of gravity in these obsolete units

**Math**

By the way, if you happen to know Physics: v = Vi - 32 t at top t = 0 0 = 56 - 32 t t = 1.75 seconds

**Math**

feet units drive me crazy but all right. 16 t^2 - 56 t - 1 = -h 16 t^2 - 56 t = - h + 1 t^2 - 3.5 t = - h/16 + 1/16 t^2 - 3.5 t + (3.5/2)^2 = -h/16 + 1/16 + 12.25/4 (t - 3.5/2)^2 = ...... vertex (top) when t = 3.5/2 = 1.75 seconds if they ask how high, keep going with completi...

**Math**

2 x - 2 = x^2 - x - 6 x^2 - 3 x - 4 = 0 (x-4)(x+1) = 0 x = 4 or x = -1 y = 6 or y = -4 so (4,6) and (-1,-4)

**calculus**

well first of all it asked for the intercepts where does the first one hit the x axis? x (x^2 -6 x+ 9) = 0 x (x-3)(x-3) = 0 so x axis intercepts at x = 0 and x = 3 (twice which means that is a grazing or min or max of g Where does the first one hit the g axis? when x = 0, y = ...

**PhysicsI**

thickness = .005 meter Q =0.84 * Area * (delta T) /thickness = 0.84 * 1 * 15 /.005 Joules/second which is Watts by the way

**statistics**

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

**Geography**

A "dormant" volcano is one that has not erupted for a while and is not expected to do so in the near future. It is not "extinct" though and will probably erupt sometime in the future. See: https://www.google.com/search?q=dormant+volcano+definition&ie=utf-8&...

**Homework dumping**

There has been no sign of any effort by the student to do these problems.

**calculating statistical data**

Where is your attempt to solve these problems?

**Physics**

k Q1 Q2 / d^2 d2 = .5 d1 so d2^2 = .25 d1^2 1/.25 = 4 times like charges repel and for heavens sake READ THE BOOK !!!!

**I have no idea.**

Need volume of tank and volume of a carton

**science**

It is NOT MOVING (This is a trick question) total energy = (1/2) k x^2 = (1/2)(15.6)(.04)

**Maths.literacy**

Oh, I see, you asked question above assuming I had seen this one. volume of tank = pi r^2 L = pi (2.25)(3) meters cubed 1 kiloliter = 1 meter cubed However I do NOT know the volume of a carton of milk (perhaps one liter? Perhaps half a liter?)

**Physics**

L = I omega I = m r^2 = 90 * 40^2 omega = v/r = 5 /40 so L = 90 * 40^2 * 5 /40 = 90 * 200 = 18000

**mathematics**

first one fills 1 truck /12 min second fills 1 truck/6 min so together they fill (1/12 + 2/12) trucks per min which is 1/4 of a truck per minute or four minutes per truck. Get it?

**math**

bought x gallons dining room = (x/3) gallons kitchen = 1.5 gallons living rm = 3 gallons leftover = 1.5 gallons so (x/3) + 6 = x 6 = 2 x/3 x = 9 gallons

**something wrong here I think**

You have over defined this problem. Once you say 23.5 meters in 5 seconds you have set the horizontal speed u = 23.5/5 Now if you set the angle at 35 then u = initial speed * cos 35 so solve for the initial speed However now we have a dilemna. Vi = initial speed up = initial s...

**algebra**

Hey, I did one, your turn :)

**math**

3^5 + ***** 3^4 (bx) + ****** 3^3 (bx)^2 + ........ now get binomial coefficients for fifth power from Pascal's triangle or formula 1 5 10 10 5 1 so 3^5 + 5*3^4 b x + 10 * 3^3 b^2 x^2 243 + 405 b x + 270 b^2 x^2 ......

**calculus**

Nor do I

**calculus typo**

y = x^(2/3) at x = 1 which is b y = 1^(2/3) = 1 at x = 0 which is a y = 0^0 = 0 y(1) - y(0) = 1 - 0 = 1 b - a = 1 - 0 = 1 so 1/1 = 1 so according to the mean value theorem somewhere between x = 0 and x = 1 the derivative = 1 dy/dx = (2/3) x^-1/3 = (2/3)/x^(1/3) when is that eq...

**calculus**

y = x^(2/3) at x = 1 which is b y = 1^(2/3) = 1 at x = 0 which is a y = 1^0 = 1 y(1) - y(0) = 1 - 0 = 1 b - a = 1 - 0 = 1 so 1/1 = 1 so according to the mean value theorem somewhere between x = 0 and x = 1 the derivative = 1 dy/dx = (2/3) x^-1/3 = (2/3)/x^(1/3) when is that eq...

**Calculus**

y = 2 (x+5)^3 + 7 to make this really easy you can say z = x+5 then dz/dx = 1 y = 2 z^3 + 7 dy/dz = 6 z^2 d^2y/dz^2 = 12 z so dy/dx = dy/dz * dz/dx = 6(x^2+10x+25) when is that zero ? (x+5)(x+5) = 0 x = -5 twice what is d/dx (dy/dx)? 6 ( 2 x + 10) when x = -5 2(-5)+10 = 0 so t...

**physics typo**

physics - Damon, Tuesday, July 22, 2014 at 4:37am Newton #1 - If there is no NET force, momentum is constant. Here speed is steady (I assume in a straight course) and mass is constant so net force is zero. Newton #3 - Action is equal and opposite to reaction. So Propulsion for...

**physics**

Newton #1 - If there is no NET force, momentum is constant. Here speed is steady (I assume in a straight course) and mass is constant so net force is zero. Newton #2 - Action is equal and opposite to reaction. So Propulsion force forward must be equal and opposite to resistanc...

**Math 221*revised***

You can enter that as 5' 2" in the web site I gave you: http://www.mayoclinic.org/bmi-calculator/itt-20084938

**Math 221**

http://www.mayoclinic.org/bmi-calculator/itt-20084938 You need male or female and birth date.

**Physics**

vertical problem first h = Hi + Vi t - 4.9 t^2 0 = 80 + 300 (sin 30) t - 4.9 t^2 solve quadratic for t. Use positive t, the other root was on the way up underground. then Horizontal problem at constant u = 300 cos 30 d = u * t

**Physics**

What might happen if you increased the volume?

**Physics**

http://www.schoolphysics.co.uk/age16-19/Thermal%20physics/Gas%20laws/text/Adiabatic_change_equation/index.html Note example problem with adiabatic expansion to twice volume.

**Physics**

http://www.schoolphysics.co.uk/age16-19/Thermal%20physics/Gas%20laws/text/Adiabatic_change_equation/index.html Note example problem with adiabatic expansion to twice volume.

**physics**

horizontal pull = 20 cos 60 = 10 N vertical pull up = 20 sin 60 = 17.3 N normal force = m g - 17.3 friction force = .4 (9.81 m - 17.3) = 3.92 m - 6.92 so 3.92 m - 6.92 = 10

**math**

Carrie = 1 case / 5 hours = .2 case/hr James = 1 case/3 hours = .333 case/hr together they do .533 case/hr so .2 * 1 hr + .533 * x hr = 1 case .533 x = .8 x = 1.5 hours more

**physics**

It is a loop of wire operating in a changing magnetic field, changing because sometimes the B flux is through the plane of the coil and sometimes it is parallel to the plane of the coil and no B goes through the coil. B = 1.8 Tesla B through coil = 1.8 sin 2 pi f t f = 60 so 2...

**Calc**

You are welcome.

**Calc**

You forgot dx :) Now I just did one of these a couple of questions down. This time use rectangles with the left hand height. Evaluate left hand heights of function at 12 13 14 15 spacing is one so multiply each left hand height by 1 and add

**Science**

ni sin i = nr sin r 1 sin 50 = nr sin 40 nr = sin 50 / sin 40

**Calc**

I assume you mean v(t) = t^2 + 2 I am not going to do the four trapezoids for you but I will do the integral so you know if you have done the area right. s(t) = (1/3) t^3 + 2 t + c when t = 0, let s = 0 so let c = 0 (we could chose any old starting s and resulting constant c b...

**Math**

I bet "original" is "wholesale" :) multiply original by 1.20 then by 0.75 1.2*3/4 = .9 so 145 * .9 = $130.50

**Calc**

Oh and by the way when x = 0 we have 0/1

**Calc**

df/dx = - x e^-x + e^-x = 0 for max or min within interval BUT you did not say the interval in general e^-x = x e^x 1 = x is one place where the slope is zero is the second derivative + or - ? d^2f/dx^2 = -x(-e^-x) -e^-x - e^-x = xe^-x -2 e^-x) = (1/e^x)(x-2) when x = 1 = (1/e...

**science**

force * time = change of momentum a) force = 49 * (6-0) / 3 = 98 N b) force acts on the average over one hundred meters c) work = force * distance = 98 * 100 = 9800 Joules interesting, lets see how much kinetic energy we have (1/2) m v^2 = .5 * 49 * 36 = 882 Joules s we are no...

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