Thursday
October 30, 2014

Posts by Damon


Total # Posts: 19,067

Math 221
I think I just did these above.
July 25, 2014

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
July 25, 2014

Math
I got 120
July 24, 2014

Math
Adults = .6 * 840 = 504 children = .4 * 840 = 336 504 = .7 (840 - boys)
July 24, 2014

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
July 24, 2014

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
July 24, 2014

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
July 24, 2014

Math: Zeroes
Oh, 50 factorial 50 * 49 * 48 ..... 1 3.0414093e+64 so 64 Just GOOGLE 50 factorial
July 24, 2014

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 :-)> . .
July 24, 2014

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
July 24, 2014

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
July 24, 2014

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
July 24, 2014

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 ...
July 24, 2014

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)
July 24, 2014

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 = ...
July 24, 2014

PhysicsI
thickness = .005 meter Q =0.84 * Area * (delta T) /thickness = 0.84 * 1 * 15 /.005 Joules/second which is Watts by the way
July 24, 2014

statistics
http://davidmlane.com/hyperstat/z_table.html
July 24, 2014

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&...
July 24, 2014

Homework dumping
There has been no sign of any effort by the student to do these problems.
July 23, 2014

calculating statistical data
Where is your attempt to solve these problems?
July 23, 2014

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 !!!!
July 23, 2014

I have no idea.
Need volume of tank and volume of a carton
July 23, 2014

science
It is NOT MOVING (This is a trick question) total energy = (1/2) k x^2 = (1/2)(15.6)(.04)
July 23, 2014

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?)
July 23, 2014

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
July 23, 2014

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?
July 23, 2014

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
July 23, 2014

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 ...
July 23, 2014

algebra
Hey, I did one, your turn :)
July 22, 2014

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 ......
July 22, 2014

calculus
Nor do I
July 22, 2014

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 ...
July 22, 2014

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 ...
July 22, 2014

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 ...
July 22, 2014

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 ...
July 22, 2014

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 ...
July 22, 2014

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
July 22, 2014

Math 221
http://www.mayoclinic.org/bmi-calculator/itt-20084938 You need male or female and birth date.
July 21, 2014

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
July 21, 2014

Physics
What might happen if you increased the volume?
July 20, 2014

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.
July 20, 2014

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
July 20, 2014

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
July 17, 2014

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...
July 17, 2014

Calc
You are welcome.
July 17, 2014

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
July 17, 2014

Science
ni sin i = nr sin r 1 sin 50 = nr sin 40 nr = sin 50 / sin 40
July 17, 2014

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 ...
July 17, 2014

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
July 17, 2014

Calc
Oh and by the way when x = 0 we have 0/1
July 17, 2014

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...
July 17, 2014

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 ...
July 17, 2014

Math
always multiply by one (top equal to bottom) so the units come out with the unwanted ones canceling 23 cm * (1 meter / 100 cm) note cm cancels top and bottom, left with meters besides we all know 23 cm = 0.23 meters :) b) NO !! 1000 mm / one meter = one 5 m * (1000 mm / 1 m...
July 17, 2014

physics
I bet they both hit the ground at the same time, whenever that is.
July 17, 2014

where asre the = signs?Math
I do not understand this.
July 16, 2014

Alegbra
subtract negative 40 from positive 119 or simply add 119 and 40 +119 - (-40) simplified = 119 + 40 = 159
July 16, 2014

science
Open the box and take the hard drive, or simply take the computer.
July 16, 2014

American literature
"...... community.(256)..... " What is your reference number 256 ?
July 16, 2014

calculus
Profit = Revenue - Cost P = -q^3 + 60 q^2 +(-1200+551)q - 760 dp/dq = -3 q^2 +120q - 649 zero for max or min q^2 - 40 q + 216.333... = 0 q = [ 40 +/-sqrt (1600-865)]/2 q = [40+/-27.1)/2 q = 34 or 6.5 to find out if max or min, take next derivative d^2p/dq^2 = -6q +120 at q = ...
July 16, 2014

physics 2
I do not understand. Mass of object increases above rest mass as speed of light is approached. .08 times original mass????
July 16, 2014

physics
energy to water per second = 1.86*10^8 Joules Kg water per second heated = m 1.86*10^8 = 4184 * m * 2
July 16, 2014

US Government
The answer is in the link Ms. Sue gave you.
July 15, 2014

Alegbra
It is very difficult to fit a line to one point.
July 15, 2014

Alegbra
both sides are 0 at (6,-8) then y goes down 5 times as fast as x goes up check: from that point go right 1 and down 5 (7, -13) is that on the line? -13 + 8 = ???? -5 (7-6) -5 = -5(1) sure enough
July 15, 2014

Alegbra
y = m x + b 7 = 0 + b b = 7 so y = -6 x + 7 where does that hit x axis ? 0 = -6 x + 7 x = 7/6 so (7/6 , 0) draw line through (7/6 , 0) and (0 , 7)
July 15, 2014

Geometry
2 pi r = 2 pi (2x) = 4 pi x
July 15, 2014

Physics mit 2.01x
No (former MIT professor), I do not do MITx problems in Course 8 or Course 2. You are on your own. The 8.01x crowd swamped this board the last time around.
July 15, 2014

science
pi r^2 h pi 1*1*12 = 12 pi cm^3 or cc = 37.7 cubic centimeters
July 15, 2014

physics
a) Huh? at x = 0 and t = 0 , y = 0 so the phase constant is 0 b) at x = .0229 m and t = .197 .745(.0229) - 42.9(.197) = -8.434 radians = -482 degrees which is -360 - 123 degrees
July 15, 2014

physics
well, first do the vertical problem, the ball how long does it take to fall 20 m? 20 = (1/2) (10) t^2 t^2 = 4 t = 2 seconds so it will take to seconds to fall. By symmetry it will also take 2 seconds to rise and hit the plane how fast is it going when it hits the ground? u = a...
July 15, 2014

physics
by the way part B is also the average speed times the time x = 5.25 * 5.2
July 15, 2014

physics
a = change in velocity / change in time = ( 0 - 10.5) / 5.2 m/s^2 x = (1/2) a t^2 = (1/2) * a from above * (5.2) * (5.2)
July 15, 2014

SCI 207
I suppose those are the people with expensive houses on the shore. However what is meant by "worst impacts"? If it means losing the most money it may be correct. However wealthy people probably can survive the loss of shore side property without ending up homeless. ...
July 15, 2014

physics
To go from km/h to m/s divide by 3.6 which is 1000 m/km / 3600 s/min a = change in velocity/time (note it is negative) F = m a By the way, this ignores wave resistance which would be a major part of the retarding force.
July 15, 2014

chemistry
P1 V1 = P2 V2 so V2 = P1 V1/P2 I am assuming that these are total pressures and no "gage" pressures. If they are gage pressures add 1 atm to both P1 and P2
July 15, 2014

physics
well, I guess it is ok to use g = 9.81 m/s^2 but we will have to check later if the thing is a significant fraction of an earth radius high. (1/2) m v^2 = m g h v^2 = 2 g h h = v^2/19.6 = 49*10^4 / 19.6 = 25,000 meters that is a small fraction of earth radius so constant g ...
July 13, 2014

Physics
Look below
July 13, 2014

Physics
If I have this picture right block one on the incline is pulling block two on the level above toward the incline. There is one force pulling block one down the incline and string tension T holding it back Fpull = 4.4 g sin 30 = 2.2 g 2.2 g - T = mu * 4.4 g cos 30 I assume that...
July 13, 2014

Physics
1 g/cm^3*1kg/1000 g* 100*100*100 cm^3/m^3 = 1000 kg/m^3 you know this anyway because the density of fresh water is about 1 g/cc or 1000kg/m^3
July 13, 2014

Math 221
well, if it ends in 0 or 5, divide by 5 26 / 21 that is 13*2/7*3 so there is nothing more to be cancelled.
July 13, 2014

American Government
This is not my field but one thought crosses my mind immediately. It is in the interest of each state to have as few welfare recipients as possible. Therefore each state would feel pressure to provide as little help as possible hoping that the people will decide to move to ...
July 13, 2014

Science
If you do A and the bread gets moldy with no air, then the mold spores probably did not come from the air.
July 13, 2014

Science
Graph that P V 8 1 4 2 2 4 1 8 Every time you cut the volume in half you double the pressure P V = k = 8 so P = 8/V so yes, confirmed
July 13, 2014

math
a bit over ten gallons a week at about three dollars per gallon = $30
July 13, 2014

math
out of every seven candies 5 are red and 2 are green so out of 5*7 = 35 candies 5*5 = 25 are red and 5*2 = 10 are green B.
July 13, 2014

physics
vertical problem (time and speed same as 104 meter fall): v = Vi - 9.81 t 0 = Vi - 9.81 t t = Vi/9.81 104 = (1/2) g t^2 104 = (1/2) (9.81)(Vi^2/9.81^2) Vi^ = 2 * 9.81 * 104 Vi = 45.2 m/s horizontal problem (constant speed) t = Vi/9.81 = 4.61 seconds u = 53/4.61 = 11.5 m/s tan...
July 13, 2014

physic
Because I believe that is the correct value for radius of the earth.
July 13, 2014

physic
for earth for example F = G M1 M2 /r^2 = (6.67*10^-11)(5.98*10^24)(67.5)/ (6.38*10^6 )^2 = 66.14 * 10^ 1 = 661 Newtons that better be pretty close to m g or 67.5*9.81 = 662 Newtons
July 13, 2014

physic
F = G M1 M2 / d^2 where G = 6.67*10-11 N m^2/kg^2 I think you mean radius for distance radius of earth = 6.38*10^6 meters
July 13, 2014

Physics
Hey look. I showed you how to do it for the earth mass and man mass. Do the same for the two balls .3 m apart. G * .3 *.3 / 3^2 = G
July 13, 2014

Physics
This is the same as your problem above with the different planets and the weight of the man on each.
July 13, 2014

Physics
same as problem above
July 13, 2014

physic
1609/4.740 and 1609/4.695
July 13, 2014

physic
x = 6 t + (1/2)(2) t^2 = 6(8) + 64 = 112 meters
July 13, 2014

history
import duties ?
July 13, 2014

Math
total area of patio = 240 area of garden = x^2 useable patio area = 12 - x^2 if x is more than 12, you can not walk around the garden
July 13, 2014

physics
better get a CD and try it :)
July 12, 2014

physics
ok, well if I have it right the pin is at the edge of the hole, 0.75 cm above the center of gravity of the CD for a small angle A the restoring moment about that pin is -m g (.0075)sin A = -.0075 m g A = -.0075*.017*9.81 A = -.00125 A the moment of inertia of the CD about its ...
July 12, 2014

physics
sorry, I need a picture.
July 12, 2014

physics
By the way magnetic field lines usually are draw going from N to S OUTSIDE the magnet.
July 12, 2014

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