Wednesday
September 17, 2014

Posts by Damon


Total # Posts: 18,517

Precal
r = sqrt (74) theta = tan^-1 (5/7) leave it that way, do not go to degrees 2 r = 2 sqrt(74) draw this axis system to figure out tan theta+pi/2 we are in Quadrant 2 theta degrees from the y axis so now tan of new theta = 7/-5 and we have the point ( 2 sqrt 74 , tan^-1 (-7/5) ...
August 9, 2014

Precalculus
and no it is the whole ellipse
August 9, 2014

Precalculus
.... and how did you make out with the spherical coordinates problem Aditya?
August 9, 2014

physics
First crossing: time to cross = 87/1.5 = 58 seconds so speed of current = 30/58 = .517 m/s second crossing v upstream = 1.5 sin A = .517 sin A = .345 A = 20.2 degrees then if they ask: v across = 1.5 cos A
August 9, 2014

physics
Yes, I am getting a bit frayed around the edges as well.
August 9, 2014

physics
(c) v = sqrt (2 g h)
August 9, 2014

physics
Thrust phase: v = a t v = 17 t v at 20 s = 17 * 20 = 340 m/s (Vi for next phase) h = (1/2) a t^2 = (1/2)(17)(400) = 3,400 m coast up phase: v = Vi - a t v = 0 at top 0 = 340 - 9.81 t t = 34.7 seconds coasting up now 54.7 seconds aloft how high? h = 3,400 + Vi t - 4.9 t^2 h = 3...
August 9, 2014

physics
It takes her 87/1.5 seconds to cross the current flows 30 meters in 87/1.5 seconds so the current speed is 30 *1.5 /87
August 9, 2014

physics
This does not make sense. The only thing I can say is that it has a mass of m = 5.10/9.81 = .52 kilograms wherever it is. Is the spaceship in a "zero gravity" orbit around earth? In that case it still has a gravitational force depending on how far from the center of ...
August 9, 2014

physics
speed across = 7.4 cos 24.8 time = distance/speed = 26.1 / 7.4 cos 24.8 the river speed only says how far downstream he will end up.
August 9, 2014

physics
moved along three sides of square? say 25 m east, 25/15 s then 25 m north, 25/15 s then 25 m west, 25/15 s so displacement is 25 m north in 75/15 s 25 * 15/75 = 15/3 = 5 m/s north
August 9, 2014

Math
If Efram is 63 that is 63 - 52 = 11 years later then Cole is 11 + 25 = 36 so it is indeed in 11 years but 11 not 63, is the answer
August 8, 2014

Math
sure but put it as a new question because we do not always look back
August 8, 2014

Math
x in the pocket to start then 4 + 2 x then 2 (4 + 2 x ) = 100 8 + 4 x = 100 4 x = 92 x = 23
August 8, 2014

MATH
multiply both sides by 12 (the least common multiple of 3 and 4) . 9 x = 2 x = 2/.9 = 20/9
August 8, 2014

algebra
but if you insist on estimating call it 35 / 3 :) which is about 12
August 8, 2014

algebra
it is so fast to say 7 1/5 is 36/5 that I call estimating here going kind of out of my way :)
August 8, 2014

algebra
36/5 / 3/5 = 36/3 = 12
August 8, 2014

Algebra
2.5 * 60 = 150 minutes 30 + .05*150 = 30 + 7.5 = $ 37.50
August 8, 2014

algebra
lol just did 36/5 / 3/5 = 12
August 8, 2014

By the way
Other than that - Good job !
August 8, 2014

Precalculus
http://mathworld.wolfram.com/SphericalCoordinates.html
August 8, 2014

Precalculus
are you sure z is not r cos phi in math theta is usually i the xy plane x = r sin phi cos theta y = r sin phi sin theta z = r cos phi In engineering and physics these conventions are often different, nut I suspect you should be using phi as the angle down from the z axis, not ...
August 8, 2014

math
9 x were boys 8 x were girls 17 x total originally 4 x girls left so then there were 9 x boys 4 x girls 13 x total 9 x - 15 = 4 x 5 x = 15 x = 3 I guess you can do 17 x and 4 x
August 8, 2014

Algebra
I started with Calculus first as well, but changed my mind after drawing the picture.
August 8, 2014

Algebra
angle from x axis to tangent = 45 + sin^-1 ( sqrt 6/3sqrt2) = 45 + 35.3 = 80.26 deg x = 2 sqrt 3 * cos 80.26 y = 2 sqrt 3 * sin 80.26 y/x = tan 80.26 = 5.82
August 8, 2014

Algebra
whoops, sorry h^2 = 18 - 6 = 12 h = 2 sqrt 3
August 8, 2014

Algebra
draw circle, center at (3,3) radius sqrt 6 draw line (hypotenuse it turns out) from (0,0) to (3,3), length is 3 sqrt 2 draw our tangent, hits circle at 90 degree angle to radius to that point, length is h so h^2 = 18 + 6 = 24 h = 2 sqrt 6 I think you can figure out the ...
August 8, 2014

Algebra
where does the tangent to the circle from the origin hit the circle?
August 8, 2014

Ethics
The first one is just accusatory, which just elicits a defensive response. The second one requires that the wrong doers be religious. We can not count on that. Who knows where intuition will lead? So I suppose I will have to agree with you.
August 8, 2014

math
aaarrrggghhhh, feet and inches and stuff :( anyway if g = -32 ft/s^2 then I will have to admit that the distance fallen from a still start is s = 16 t^2 (not r^2 by the way, falls straight down, not in a circle) s = 16 (64) = 1024 answer B which we did not need a calculator ...
August 8, 2014

math
well, if one were a prime number then 1986 would do BUT since it is not (any number greater than one not divisible by anything but ---), then 1987 would do since surely 2 is a prime number.
August 8, 2014

maths
x^2 = (c-b)/a ? x = sqrt [(c-b)/a] well, (c-b)/a better be positive and a square of some integer (which makes it positive anyway) for example if (c-b)/a = 5 then x = sqrt 5 which is hard to express as a ratio of integers and if (c-b)/a is -4 then we have 2 i and i, the square ...
August 8, 2014

Math (fibonacci
It would help if that last date were odd :)
August 8, 2014

Math (fibonacci
By the way I suspect you mean 2000 not 200
August 8, 2014

Math (fibonacci
y = 1985 + x 200 = x + y so 200 = x + (1985+x) back to you :)
August 8, 2014

Physics
yes, good to remember v = -sqrt (2 g h) here v = -sqrt (2*9.81*.75) = -3.84 m/s 1.7 = sqrt (2 *9.81 * h) h = .1472986748 I think g is 9.81, you use 9.8 some classes use 10
August 8, 2014

science
I think I know what you mean. If you calculated the time until the ball reached maximum height and called that time t, then the total time in the air is 2t by symmetry
August 8, 2014

science
yes they both start with Vi = 0 and accelerate downward at 9.81 m/s^2
August 8, 2014

Physics
You are welcome.
August 8, 2014

Physics
yes, 0 = 42 + 75 a a = - .56 d = Vi t + .5 a t^2 d = 42(75) - .28(75)^2 = 3150 - 1575 = 1575
August 8, 2014

History
I do not see a problem in using the same things as answers an earlier question. You have me pretty confused though about what you think are advantages and disadvantages of ethnic neighborhoods. What do you think are advantages and what do you think are drawbacks?
August 7, 2014

History
cultural diversity and learning new cultures would not particularly be an advantage of an ethnic neighborhood. A family that moved into a mixed neighborhood would probably learn the new language and traditions faster. I would say advantages include mutual support both in ...
August 7, 2014

what is the question ?
You want zeros of y or what? if zeros: 4 x^2 - 12 x + 9 = 0 (2 x-3)(2x-3) = 0 x = 1.5, 1.5 double root If vertex etc: 4 x^2 -12 x = y - 9 x^2 - 3 y = (1/4)(y-9) x^2 - 3 y + 9/4 = (1/4)y (x-1.5)^2 = y/4 vertex at (1.5 , 0) which we knew already
August 7, 2014

physics
Well, there is a hard way and an easy way. Easy way height = h angle = A with no friction KE gained in slide = m g h (1/2) m v^2 = m g h v = sqrt (2 g h) average speed = v/2 = .5 sqrt (2 g h) time = average speed * h/sin A t = .5 h sqrt (2 g h) /sin A now with work done ...
August 7, 2014

math
12.5= 3/k multiply both sides by k 12.5 k = 3 divide both sides by 12.5 k = 3 / 12.5
August 7, 2014

physics whoops
Whoops, sorry, Steve is right.
August 7, 2014

physics
since the total displacement vector is zero the average speed is zero. let i be unit vector from point A to point B velocity outbound = 40 i velocity back = -60 i (40 - 60)/2 = -10
August 7, 2014

Math
5*4
August 7, 2014

Math
I did one of these for you. They are fundamentally all the same. The circumference of a circle is 2 pi r The area of a circle is pi r^2 Hey, draw a picture.
August 7, 2014

Math
6 w = 18 w = 3 so r = 3 A = pi r^2 = 9 pi
August 7, 2014

math
16 * 8 * 8
August 6, 2014

math corrections
I do not understand number 2. Typo? 4) .75/2 -.625/2 = .0625 (radius not diameter is used) 14) I get 40 (long, will elaborate later) 24) (30/250)(30) = 3.6
August 6, 2014

Algebra
2.68*10^-5 watts/cm^2 to dB You want Watts/m^2 so multiply by 10^4 2.68 * 10^-1 Watts/m^2 definition of dB for sound: dB = 10 log (watts/m^2 intensity /10^-12) = 10 log (2.68*10^11) =10 [ log 2.68 + 11 ] = 10 [ 11.428 ] = 114 dB LOUD !!!!
August 6, 2014

Physics
displacement vector / time
August 6, 2014

physics
Force = change in momentum / change in time if force the same and time the same then change in momentum the same (answer to first question) f = m v /t f = 2 m V /t so V = v/2 Ke of little mass = (1/2) m v^2 Ke of big mass = (1/2) 2m v^2/4 =(1/2)m v^2/2 so Ke of big mass = 1/2 ...
August 6, 2014

PHYSICS
increase of potential energy of block = m g h = (2.515)(9.81)(.15) = 3.70 Joules so (1/2) m v^2 = 3.7 Joules at bottom (1/2)(2.515)v^2 = 3.7 v = 1.72 m/s at bottom after collision momentum after collision = 2.515 * 1.72 = 4.31 g m/s momentum before collision = .015 v so v = 4....
August 6, 2014

physics
change those to meters / second (1/2) m (V2^2-V1^2) note 6^2 - 5^2 = 36-25 = 11 but 3^2 - 1^2 = 9 - 1 = 8
August 6, 2014

physics
v = sqrt (2 g h) = sqrt (2 * 9.81*12) a ) Ke = (1/2)(45) v^2 b ) stops in .32 m work = Force * .32 = Ke from part a
August 6, 2014

physics
momentum down = 1.2 *25 momentum up = 1.2 * 10 change of momentum = 1.2 (25 + 10) impulse is change of momentum Force = change in momentum/change in time = answer to part a / .2
August 6, 2014

statistics
I get .8186 between 24 and 48 so about 819 out of 1000
August 6, 2014

statistics
http://davidmlane.com/hyperstat/z_table.html
August 6, 2014

SCIENCE
http://www.jiskha.com/display.cgi?id=1407333641
August 6, 2014

SCIENCE
aaarrrgghhh 1.5 (9.81) h = 29.4 still
August 6, 2014

PHYSICS
work = increase in kinetic energy = (1/2)(18,000) (40^2 -30^2) in Joules force * distance = work in Joules distance = average speed * time d = 35 * 5 so Force = work from part a / d power = work/time = work from part a / 5 seconds in Joules/sec which is Watts
August 6, 2014

PHYSICS
You are welcome.
August 6, 2014

PHYSICS
http://www.jiskha.com/display.cgi?id=1407324138
August 6, 2014

PHYSICS
Hey, I just did this
August 6, 2014

PHYSICS
Newton #2 is Force = rate of change of momentum 6 = 3 (v-0) /10 solve for v final momentum = m v
August 6, 2014

PHYSICS
I guess it is hanging down on earth where g = 9.81 m/s^2 approximately F = m g = k x 2.5 * 9.81 = k (.42) solve for k b) F = k (0.50) c) U = (1/2) k x^2 = (1/2)(k)(0.35)^2
August 6, 2014

SCIENCE
m g h = 29.4 1.5 * 9.81 * h = 29.4 solve for h
August 6, 2014

math
Looks like magic to me.
August 6, 2014

Physics
no kinetic energy lost in collision Not only is momentum conserved but also sum of (1/2) m v^2
August 6, 2014

Physics
1) sqrt (20^2 + 30^2) 2) no horizontal force so no change in horizontal speed 3) slows to zero at top then comes back to original speed but downward 4) Like we said in #2, it is the same until it hits the charging warthog. 5) it is at max height, no speed up any more and no ...
August 6, 2014

Physics
.005 (300) = - 3 v v = -.5 Ke = (1/2)(.005)(300)^2 + (1/2)(3)(-.5)^2
August 6, 2014

math
Hey, look, you are not paying attention. it has highest power of 3 so three factors and three zeros however one of those zeros is repeated, x = -1 so zeros are -1, -1 , -1/2 and the three factors are (x+1) (x+1) (2x+1) now check by multiplying those three factors and see if ...
August 6, 2014

math
I gave you the whole thing factored (x+1)(2x+1)(x+1) zeros are -1 , -1/2, -1
August 6, 2014

math
try x = -1 for a zero 2(-1) + 5(1) + 4 (-1) + 1 -2 + 5 - 4 + 1 0 so (x+1) is a factor, now divide (x+1)(2x^2 + 3x + 1) (x+1)(2x+1)(x+1)
August 6, 2014

physics
He has a Uranium mine.
August 6, 2014

physics
mass irrelevant 78.4 = (1/2) g t^2 t^2 = 2 * 78.4 / 9.81
August 6, 2014

Copy and paste does not work here
We can see neither your equation nor the "following statements".
August 6, 2014

math
(1/5)(V+W+X+Y+Z)
August 6, 2014

Math
2(81) - 3(9) - 8(3) + 4 = 115
August 5, 2014

math
3 - 4 - 2 - 8/15 -45/15 -8/15 -53/15
August 5, 2014

physics
The horizontal component of velocity DOES NOT CHANGE There is no horizontal force. Therefore there is no horizontal acceleration.
August 5, 2014

Finance Help
In the end, looking far ahead, the value of a share of a company is the present value of a future stream of dividends. Of course people do not think much about that for most stocks, particularly those that presently pay no dividends, because there are so many other factors ...
August 5, 2014

Math
Nope, C 1.5 inches
August 5, 2014

Math
L = 10 - 2x w = 8 - 2 x v = L * w * x v = (10-2x)(8-2x)x v = (80 - 36 x + 4 x^2)x v = 4 x^3 - 36 x^2 + 80 x do you do calculus? if so the min or max when dv/dx = 0 0 = 12 x^2 -72 x + 80 0 = 3 x^2 - 18 x + 20 x = 3 +/- (1/3)sqrt 21 = 3 +/- 1.52 the plus sign is too big a width ...
August 5, 2014

History
You are welcome ;)
August 5, 2014

History
How much does this machinery cost? Assuming money was borrowed from the bank to buy it all, how do the loan payments compare with the monthly payments to the bank for the farm land and the house and barn? Does the cost of this equipment force you to buy a much bigger farm than...
August 5, 2014

Algebra
149.25 = x - 0.25 x 149.25 = 0.75 x x = 149.25 / 0.75
August 5, 2014

math hw
20/60 = 1/3 of an hour distance = speed * time 160 miles = speed * (1/3) hour speed = 3 * 160 miles/hour = 480 miles/hour
August 5, 2014

Pre Cal
100 at 50 degrees counterclockwise from x 50 at 160 counterclockwise from x x component = 100 cos 50 + 50 cos 160 = 64.28 - 46.98 = 17.30 y component =100 sin 50 + 50 sin 160 = 76.60 + 17.10 = 93.70 magnitude = sqrt (17.30^2 + 93.70^2) angle = tan^-1 (93.70/17.30)
August 5, 2014

Math
You are welcome. Good luck !
August 5, 2014

Math
Here: http://www.purplemath.com/modules/mtrxmult.htm
August 5, 2014

Math
|24 -12| |0 +3 | |-18 -9|
August 5, 2014

Math
Well, if you multiply a matrix by a scalar, you multiply every element by the scalar
August 5, 2014

Math
Perhaps nothing. I need to figure out what the question is :)
August 5, 2014

Math
Oh like this? | -8 +4 | -3| +0 +3 | | +6 +3 | now does it want the product or -3 times the determinant I wonder ?
August 5, 2014

Math
Anyway --- go here : http://matrixcalc.org/en/
August 5, 2014

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