Wednesday

September 17, 2014

September 17, 2014

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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