Monday
November 24, 2014

Posts by Damon


Total # Posts: 19,424

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

physics
1. How would they cross? 2. different constants/r^2 k Q1 Q2/r^2 versus G M1 M2/r^2 see https://www.google.com/search?q=exponential+field+definition&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=sb#channel=sb&q=exponential+function+definition&...
July 12, 2014

whoops
14.4 *10^-9 = 1.44 *10^-8
July 12, 2014

physics
k Q/r 9*10^9 * 1.6*10^-19/10^-1 14.4 *10^-9 = 1.44 *10^-10
July 12, 2014

algebraic expression
I don't know.
July 12, 2014

physics
yes, looking for ratio of charge to mass, knowing mass, could calculate charge (slight oversimplification) see: http://ffden-2.phys.uaf.edu/212_fall2003.web.dir/Ryan_McAllister/Slide3.htm
July 12, 2014

physics
potential energy of mass m at surface = -GMmoon m/r = - m (6.67*10^-11) (7.35*10^22) /(1.74*10^6) = m (28.2*10^5) Needs that many Joules of Ke so (1/2) m v^2 = 2.82*10^6 m v^2 = 5.64 *10^6 v = 2.37*10^3 = 2370 m/s by the way: http://www.1728.org/escvel.htm
July 12, 2014

physics
You are welcome.
July 12, 2014

physics
E = 9*10^9 Q/r^2 here Q = 1.6*10^-19 so 9*10^-3 = 9*10^9 (1.6*10^-19)/r^2 r^2 = 1.6 * 10^-7 = 16 * 10^-8 r = 4*10^-4 meters = .4 millimeters
July 12, 2014

Math
using that regression line calculator y = -4.29x + 28.3 (2.5, 17.6)
July 12, 2014

Math
http://www.alcula.com/calculators/statistics/linear-regression/
July 12, 2014

Math
same as above. enough already.
July 12, 2014

Math
It would take you less time to do these problems than to post them.
July 12, 2014

Math
Your problems are all answered by the link I gave you.
July 12, 2014

Math
tan(90-39) = AP/40 so AP = 49.4 tan (90-52) = BQ/40 so BQ = 31.2 so P is (49.4-31.2) or 18.1 km south of Q and 40 km west of q tan theta = 40/18.1 theta = 65.7 degrees east of north from P to Q
July 12, 2014

Math
http://davidmlane.com/hyperstat/z_table.html
July 12, 2014

Math
The link I gave you does all of these. In fact if you have a normal table handy, all your questions are really answered in it.
July 12, 2014

Math
Use link below for normal curve: http://davidmlane.com/hyperstat/z_table.html
July 12, 2014

Math
http://davidmlane.com/hyperstat/z_table.html
July 12, 2014

Math
122 z = (122-182)/30 = -2 242 z = (242 - 182)/30 = +2 then use normal table or use: for example http://davidmlane.com/hyperstat/z_table.html result .9545 in that range so .9545*600 = 573
July 12, 2014

Math
http://davidmlane.com/hyperstat/z_table.html
July 12, 2014

Dynamics
d^2x/dt^2 = 2 t - 1 dx/dt = t^2 - t + c at t = 0, dx/dt = 2 so c = 2 so v = dx/dt = t^2 - t + 2 x = (1/3) t^3 - (1/2) t^2 + 2 t + c when t = 0 x = a so c = 1 x = (1/3) t^3 - (1/2) t^2 + 2 t + 1 so at t = 6 v = 36 -6 + 2 = 32 m/s and x = 67 total distance = 67-1 = 66 assuming x...
July 12, 2014

Hunting training
So would I (but I know nothing about this really)
July 12, 2014

Hunting training
I agree because my spaniel won't hunt.
July 12, 2014

PHYSICS
at ten meters it has dropped 15 meters (1/2) m v^2 = m g h v^2 = 2 * 9.81 * 15 = 294.3 v = 17.2 m/s at 10 m above ground d = (1/2) g t^2 25 = 4.9 t^2 t = 2.26 seconds
July 12, 2014

science
walk north until the arrow flips :)
July 12, 2014

science
...... but not found yet
July 12, 2014

science
The magnetic monopole is a much sought after object :)
July 12, 2014

science
http://cosmoquest.org/forum/showthread.php?91956-The-Moon-Specular-and-Diffuse-Reflection
July 12, 2014

science
It is called reverberation. See: http://www.wisegeek.com/what-is-a-reverberation.htm#didyouknowout
July 12, 2014

Math
You are welcome.
July 12, 2014

Math
to fit in the box the radius of a round pizza must be less than or equal to 6 inches A = 3.14159 * r^2 = 3.14159 * 36
July 12, 2014

PHYSICS
F * 100 / 80 = 200
July 12, 2014

chemistry step by step for me clearly
sorry 3 * 6 = 18 mols
July 12, 2014

chemistry step by step for me clearly
I have to assume you mean 2.684 grams of Al2(SO4)3 and water per cc. One of those grams is water so we have 1.684 grams of Al2(SO4)3 in every cc Al2(s04)3 How many grams per mol? 2 Al = 2 * 27 = 54 3 S = 3 * 32 = 12 O = 12 * 16 = 192 so Al2 (SO3)4 = 278 grams/mol If we have 1....
July 12, 2014

Physics
How fast can the stack accelerate without the books above the first one slipping? weight down on bottom book = 5 * 4 kg * g maximum static friction force between top 5 and bottom book = 5 * 4 * g * 0.3 so max force = mass of top 5 * a 5*4*g*.3 = 5*4 * a so a = .3 g that gives ...
July 11, 2014

electric circuit
Interesting, went nameless :)
July 11, 2014

Trigonometry
A(of L and w) = L * w if w = 1 then A(L) = L
July 10, 2014

stats
57.21% or .5721
July 10, 2014

stats
I think the same as the probability that one is more than 2.90 mean = 3 we are at .1 below mean Z = -.1/.55 = -.18 from normal table if Z = -.18 then F(z) about .421 so about 42% are below so about 58 % are above 2.9 For accurate table use http://davidmlane.com/hyperstat/...
July 10, 2014

error
arithmetic! (10*9*8)/(16*15*14) = .2143 1 - .2143 = .7857
July 10, 2014

Math
p = probability defective = 6/16 = .375 1 - p = 10/16 = .625 = probability good we do three trials on the box. They all must be good if it is to pass probability of first trial fuse good = 10/16 probability of second choice being good fuse = 9/15 third = 8/14 so probability of...
July 10, 2014

No picture
If you tried to copy and paste, that does not work here.
July 10, 2014

US Government
However in real life they seem to be closer to: http://www.constitutionparty.com/our-principles/key-issues/
July 10, 2014

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