Monday
April 20, 2015

Posts by Damon


Total # Posts: 20,912

physics... PLEASE HELP
well, it is late but I might be able to point a direction average intensity = average power / (pi r^2) Peak = twice average power if a sine wave [ average of sin^2 = (1/2) ] energy density usually in Joules per square centimeter where it hits I assume per second. That would be...
October 15, 2014

Physics - Second Law Question
same as the other question (3-1.96)10^5 Newtons up
October 15, 2014

Physics - Second Law Question
4.9 - 4.5 = 0.4 0.4*10^-3 = 4 * 10^-4 down because weight is bigger than drag up
October 15, 2014

Physics
NO!! Usually in a given problem the SUM of kinetic and potential energy is more or less constant. I say more or less because energy is easily lost from your nice neat problem through friction or escape of heat or whatever messy thing happens to make your car not coast forever ...
October 15, 2014

Math
(7/8)hr/(3/4) puzzle = 7/6 hours/puzzle or 6/7 puzzles/hour
October 15, 2014

Pre-Calc/Trig...
b^2-4ac 5^2 -4(2)(-3) that will be positive and therefore its square root is a real number. Thus two real roots, nothing imaginary about it 1^2 - 4(-1)(1) everything positive again, two real roots
October 15, 2014

Physics
x momentum after = x momentum before after p = 38 (6.06 cos 10.5) + 2.37 v before p = (38+2.37)(5.07) set equal, solve for v which will probably be negative (kid goes forward, board goes backward)
October 15, 2014

Pre-Calc/Trig...
4 sqrt -1 = 4i 7 sqrt -1 = 7i
October 15, 2014

Math
do you mean??? [(-3) ^-4 ] [ 5 ^-2 ]=? if so [1/(-3^4 )] (1/25) (1/81)(1/81)(1/25)
October 15, 2014

Algebra 2
1+6+11 = 18 = 2/3 of cast so cast = 27 27 - 18 = 9 which is indeed 1/3 of the cast
October 15, 2014

Algebra 2
cost = c Briana + 73 = c Molly + 65 = c Briana + Molly = c so molly = (c - Briana) now we have Briana + 73 = c (c - Briana) + 65 = c or Briana = 65 Briana + 73 = c 73 + 65 = c = 138
October 15, 2014

Science
been there, done that http://www.jiskha.com/display.cgi?id=1413411282
October 15, 2014

Mechanics
x velocity = 15 across y velocity = .9 downstream note order of answers c. time to cross = 500/15 = 33.33 seconds b. downstream y = .9 * 33.33 = 30 meters a. sqrt (.9^2+15^2) angle to x axis = A = tan^-1(.9/15) d. sin^-1 (.9/15) toward upstream e. component of speed across = ...
October 15, 2014

math
n-2, n, n+2 4(n-2) - n = 12 + 2(n+2) 4 n - 8 - n - 12 - 2n - 4 = 0 n - 24 = 0 n = 24 22 , 24, 26
October 15, 2014

Math
let z = cos A 4 z^2 - 3 z = 0 z(4z-3) = 0 z = 0 or z = 3/4 so cos A = 0 when z = 90 degrees cos A = 3/4 when z = 41.4 degrees but that is not between 90 and 180
October 15, 2014

Algebra Help
(2x+5)^.5 - (x+6)^.5 = 1 you mean maybe, parentheses missing if so (2x+5)^.5 = 1 +(x+6)^.5 2x+5 = 1 + 2 (x+6)^.5 + x+6 (x - 2) = 2 (x+6)^.5 x^2 - 4 x + 4 = 4 x + 24 x^2 - 8 x - 20 = 0 (x-10)(x+2) = 0 x = 10 or x = -2 go back and see what works in the original now.
October 15, 2014

algebra
1. let z = x^2 then yo have 4 z^2 - 4 z + 1 (2z-1)(2z-1) which is (2x^2-1)(2x^2-1) 2. a^2 (a^2+1)
October 15, 2014

algebra
(x+3)(x-2) 3*5 = 15 which differs from 113 by 2 so (3x-1)(2x+5)
October 15, 2014

Linear Algebra
.866 is sin 60 by the way
October 13, 2014

Linear Algebra
L1 = 1 L2 = -.5 - .866 i L3 = -.5 + .866 i eigenvectors messy see http://www.wolframalpha.com/widgets/view.jsp?id=9aa01caf50c9307e9dabe159c9068c41
October 13, 2014

Algebra 2 Answer Check
just put in a bunch of cost values from 0 to 10 if the cost were $2 change = 8 cost - change = 2 - 8 = -6 and 10 - 2(8) = -6 It is only non-negative if the cost is between 5 and 10
October 13, 2014

Algebra 2 Answer Check
I misread it cost = 10 - change cost - change = 10 - 2 change
October 13, 2014

Algebra 2 Answer Check
Huh f(x) = 10 - x
October 13, 2014

Algebra 2
You are right, there is no solution to #1
October 13, 2014

Algebra 2
Oh, I see, you are right. no positive divided by -5 could be + 6
October 13, 2014

Algebra 2
-26/3 is negative 34/3 is positive but they could both be negative anyway
October 13, 2014

Algebra 2
By the way to graph that parabola y = 5 x^2 - 8 x + 11/3 http://www.wolframalpha.com/input/?i=5+x^2+-+8x+%2B+11%2F3
October 13, 2014

Algebra 2
1. (|3x -4|)/(-5) = 6 A: no solution ========================= multiply both sides by - 5 , no arrow business because just an equal sign 3 x - 4 = -30 or -3x + 4 = -30 3 x = -26 or -3x = -34 so there are two solutions
October 13, 2014

Algebra 2
6. |12 - 4x| - 4 > 20 A: x < -3 and x > 9 ============================ 12 -4 x > 24 or -12 + 4x >24 -4x > 12 or 4x > 36 x < -3 or x > 9
October 13, 2014

Algebra 2 #1 sorry
1. (|3x -4|)/(-5) = 6 (|3x -4|) = -30 or 3x-4 = -30 or -3x+4 = -30 so x = -26/3 or x = 34/3
October 13, 2014

Algebra 2
5. (-3) x (|5x - 8|)- 5 greater than or equal to 6 A: no solution? ============================ 3 (-3) x (|5x - 8|)- 5 >/= 6 (-3) x (|5x - 8|) >/= 11 x (|5x-8)| </= -11/3 x(5x-8) </= -11/3 x(-5x+8) </= -11/33 5 x^2 - 8 x </= -11/3 -5 x^2 + 8 x </= -11/3 ...
October 13, 2014

Algebra 2
4. [(|x - 2|)/ (4) greater than or equal to 5 A: -18 < x < 22 =========================== x-2 >/=20 or -x+2 >/= 20 x >/= 22 x </= -18
October 13, 2014

Algebra 2
3. |5x + 15| > 20 A: x > 1 and x < -7 5x +15 > 20 or -5x - 15 >20 x > 1 yes -5x > -35 divide both sides by -5 and reverse the arrow x < 7 why the sign ?????
October 13, 2014

Algebra 2
2. (|2x -5|) = x + 3 A: x = 8 or x = 2/3 ========================= 2x-5 = x+3 or -2x+5 = x+3 x = 8 or x = 2/3 you got that right. Why did you miss #1 ????
October 13, 2014

Algebra 2
1. (|3x -4|)/(-5) = 6 (|3x -4|) = -30 or 3x-6 = -30 or -3x+6 = -30 so x = -24/3 = -8 or x = 12
October 13, 2014

Math
2 sin T cos T cos T /sinT = 2 cos^2 T
October 13, 2014

algebra
a circle with radius 10 and center at (7,6) (x-7)^2 + (y-6)^2 = 10^2 = 100 where does it hit the y axis (y=0) ? (x-7)^2 + 36 = 100 (x-7)^2 = 64 (x-7) = +/- 8 x = 7 +/- 8 if x = 7+8 then x = 15 if x = 7-8 then x = -1
October 12, 2014

Physics
The lighter one had to be going faster. To be at 45 degrees, momentum north = momentum east 2000 v = 3000 (2v/3)
October 12, 2014

Physics 12
u = 12 cos 42 = 8.92 m/s the whole time Vi = 12 sin 42 = 8.03 v = Vi - 9.81 t h = 9.5 + Vi t - 4.9 t^2 0 = 9.5 + 8.03 t - 4.9 t^2 t = [ -8.03 +/- sqrt (8.03^2-4*-4.9*9.5)]/-9.81 t = [-8.03+/-sqrt(251) ]/-9.81 t = 2.43 s
October 12, 2014

calculus
a = area = 6 x^2 da/dx = 12 x so da = 12 x dx
October 12, 2014

calculus
Again? http://www.jiskha.com/display.cgi?id=1413057054
October 12, 2014

Nonsense
It is true that in obsolete English units H(t) = Hi + Vi t - (1/2)(32) t^2 if Hi = 72 ft and Vi = 0 then H(t) = 72 - 16 t^2 however your next line makes no sense at all. perhaps you mean when is H = -184 ??? then 72 - 16 t^2 = -184 16 t^2 = 256 t^2 = 16 t = 4 seconds
October 12, 2014

Calculus
dv = surface area * dh so dv/dt = surface area * dh/dt width at surface = 40 + (80-40)(30/40) = 40 + 30 = 70 cm = 0.70 m so surface area = 9 * .7 = 6.3 m^2 so .3 m^3/min = 6.3 m^2 * dh/dt and dh/dt = .047 meters/min or 4.7 cm/min
October 12, 2014

physics
time 2 = 1.81 * time 1 h = (1/2)gt^2 so h/t^2 = constant = H1/t1^2 = H2/t2^2 H2/H1 = t2^2/t1^2 = 1.81^2 = 3.27
October 12, 2014

College Algebra
Yes, but it is trivial p = 0 and p = 10 give R = 0
October 12, 2014

physics
m g down ramp = m g sin 28 mg normal = m g cos 28 m g sin 28 - mu m g cos 28 = m (.98) sin 28 - mu cos 28 = .98/9.81
October 12, 2014

physics
potential energy proportional to height, m g H so Hn = (1-.0534)Hn-1 Hfinal = .9466^n Hinitial 2.79 = .9466^n 5.89 .9466^n = .4737 n log .9466 = log .4737 n = 13.6 so 13
October 12, 2014

calculus
well Diagonal = D = x sqrt 2 so dD = sqrt 2 dx a = x^2 so da = 2 x dx etc
October 11, 2014

physics
horizontal force exerted = 75 cos 22 +75 cos 32 vertical force exerted = 75 (sin 32 -sin22) normal force on ground = m g - 75(sin32-sin22) friction force = mu (normal force) acceleration = 0 so friction force = horizontal force exerted work done = 13 * friction force You did ...
October 11, 2014

Math
.12/52 = .002308 so for n weeks 3 = 1.002308^n log 3 = n log 1.002308 n = 476 weeks or 9.16 years
October 11, 2014

Calculus
v = x^3 729 = 9^3 so x = 9 dv = 3 x^2 dx = 243 dx = 849.285 - 729 etc
October 11, 2014

Calculus
Hint: http://www.jiskha.com/display.cgi?id=1413053733
October 11, 2014

Trigonometry
Hint: sin 2a = 2 sin a cos a so what is 3 sin 2a?
October 11, 2014

calculus
surface area = a = 6 x^2 da/dx = 12 x so if a = 24, x = 2 da = 12 x dx = 12*2 * dx = 24 dx if da = 2.016 then dx = da/24 = .084 (answer part 1) volume = v = x^3 = 8 when x = 2 so dv/dx = 3 x^2 dv = 3 (2^2)(.084) (part b) 100 (dv / v)
October 11, 2014

Education 606
http://davidmlane.com/hyperstat/z_table.html
October 10, 2014

physicss
v = Vi + a t Vi = 0 a = -10 so v = -10 t 0 = 1980 + 0 t - (1/2)(10)t^2 5 t^2 = 1980 t = 19.9 seconds so v = -199 m/s
October 10, 2014

equation
1 1/2 = 3/2 (3/2) / 3 = 3/6 = 1/2
October 10, 2014

equation
4/3 ---- 3 is 4/9
October 10, 2014

Math
bobpursley is correct but of the answers listed B is correct. Your course evidently does not do significant figures. yet.
October 10, 2014

Math
yes
October 10, 2014

Physics
we do not have your figure.
October 10, 2014

calculus
series for f(x when a = 0: tan x = tan 0 + sec^2 0 (x) + .... = 0 + 1 x ..... when does x = tan x +/- .1 make a table of x in radians vs tan x
October 10, 2014

Algebra- please help answer
5 815/1000 6 21/1000 --------------- 11 836/1000 = 11 418/500 = 11 209/250 11.836
October 9, 2014

Algebra
.75 + .125 + .09 = .965 1.2 - .965 = .235
October 9, 2014

Algebra whoops !
11 209/250
October 9, 2014

Algebra
11 836/1000 = 11 209/1000
October 9, 2014

physics
2*10/d^2 = 4*10/(12-d)^2
October 9, 2014

physics
component of weight down ramp = 600 sin 30 = 300 pounds
October 8, 2014

No idea
I have no idea what your jockey experiment is.
October 8, 2014

physics
http://science.howstuffworks.com/transport/engines-equipment/pulley.htm
October 8, 2014

Physics
Pulling with component up on block reducing the normal force between block and floor and thus reducing friction force which is maximum of coefficient of friction times normal force.
October 8, 2014

math
I do not understand. There are only four aces in the pack. If order is not important, then there is only one way.
October 8, 2014

math
combination of 4 jacks 3 at a time C(4,3) = 4! /[ 3! (4-3)! ] = 4 combination of 4 twos 2 at a time c(4,2) = 4! /[2!(4-2)!] = 3 so 4*3 = 12
October 8, 2014

Math! Please check!
You are welcome, good luck.
October 7, 2014

Math! Please check!
Got it ?
October 7, 2014

Math! Please check!
Yes and yes To remember forever: 1. Hypothesis: If cow , then mammal 2. converse: If mammal,then cow (maybe) 3. inverse: If not cow, then not mammal (maybe) 4. contrapositive: If not mammal, then not cow (true) Make Venn diagrams for the situation :)
October 7, 2014

Math
http://davidmlane.com/hyperstat/z_table.html
October 7, 2014

math
(5/4) *120 = 5 * 30 = 150 pennies which is $1.50
October 7, 2014

math(fractions)
but 90/20 is 9/2 which is 4 1/2 which is 4.5
October 7, 2014

Algebra
It is going to be ten times as big.
October 7, 2014

Algebra
how many 125s in 8450 ? 8450 ----- = 67.6 so 67 full rows 125
October 7, 2014

Algebra
well, we sure seem to be into division :) 384,400 -------- = 110.587 so 111 3476 because .587 is more than half way from 110 to 111
October 7, 2014

Math! Please check!
I agree with all of your choices.
October 7, 2014

physics
v = Vi + a t 152 = 0 + 1.35 * 10^4 t but 1.35 * 10^4 = 135 * 10^2 t = (152/135) * 10^-2 = 1.13 * 10^-2 = .0113 seconds
October 7, 2014

What pulley system
I have no idea what your block and tackle looks like so can not calculate the mechanical advantage. Divide 1000 by the number of parts of the line pulling up on the piano.
October 7, 2014

PHY1015S
Two of them :)
October 7, 2014

Math
if you do not know calculus area of surface = pi d^2/4 area of surface * change in height/min = volume/minute pi d^2/4 * .24 m/min = pump rate - leak rate
October 5, 2014

Math
0.16 c = 4 so c = 4/0.16 = 25 then yes, subtract 4 and get 21
October 5, 2014

Confusing increase in percent
That is always confusing and the thing to remember is that doubling is 100% increase.
October 5, 2014

Math
If the result is 400% of the original 100%, then the increase is 300% +100% = doubled +200% = tripled +300% = quadrupled
October 5, 2014

Physics gr. 12
You went about this correctly. I did not check the arithmetic.
October 5, 2014

Math
+++++++ 2 x___+ 1_______ 5x-6 / 10 x^2 - 7 x - 6 ++++++ 10 x^2 -12 x +++++++++++++++ 5 x - 6 +++++++++++++++ 5 x - 6 Remainder = 0
October 5, 2014

math
at t = 0 xA = -20 , dxA/dt = -24 yA = 0, dyA/dt = 0 xB = 0, dxB/dt=0 yB = 0 , dyB/dt = 25 Dx = differnce in x location = 20 + 24 t Dy = difference in y location = 25 t distance = (Dx^2+Dy^2)^.5 distance = [ 400+480t+576t^2+ 625t^2 ]^.5 = [1201 t^2 + 480 t + 400 ]^.5 d distance...
October 5, 2014

solve long divison polynomials
http://www.jiskha.com/display.cgi?id=1412542641
October 5, 2014

probability;math
By the way, they were trying to trick you. If the Jack were NOT replaced, there would only be 51 cards when you went to pick the 8. Then it WOULD HAVE BEEN 4/52 * 4/51
October 5, 2014

probability;math
as long as it is replaced, the events are independent 4/52 * 4/52
October 5, 2014

Physics
v = Vi + a t Vend = 24 + 35 (1.9) angle at 1.9 s = 1.9(Vi+Vend)/2 total angle = 436 + angle at 1.9 s time at Vend = 1.9 + 436/Vend
October 5, 2014

Math Growth Rate w/ inflation
1.5 = (1+r)^3 log 1.5 = 3 log (1+r) 1 + r = 1.1447 r = .145 so 14.5 percent 1.08 = 1.1447^n find n continuous 1.5 = e^3k ln .5 = 3 k
October 3, 2014

Physics
4.92/360 = 500/c c = 36,585 km approximate check a degree on a great circle (around any circumference) of earth is 60 nautical miles :) (1.852 kilometers / naut mile) 360 * 1.852 * 60 = 40,000 close enough
October 3, 2014

Math
3.647 - 3.003 = 0.644 = 0.6
October 3, 2014

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