Friday
September 4, 2015

Posts by Damon


Total # Posts: 21,884

chemistry
Use what Dr Bob said
July 31, 2015

chemistry
CaCO3 + HCOOH = H + CaCOOH + CO3 of course that needs H2 on the right so double everything if writing a balanced equation
July 31, 2015

College Algebra
Are you sure? The air resistance is more like proportional to velocity square. However it does not matter since you do not need to know. v(0) = 180 * (1- e^0) but anything to the 0 is 1 so v(0) = 180 (1 - 1) = 0 v(5) = 180(1 - e^-1.15) = 180(1-.317) = 123 v(10) = 180 (1 - e^-2...
July 31, 2015

Math 157
11^5 * 3^5 * 3^1 * 13^1 * (5^2)^12 3^6 * 5^24 * 11 * 13
July 31, 2015

problem solving
.71 J/g C * 2 g * 100 C = 142 J
July 31, 2015

Science
I agree, low density gas due to high temp and low compressing gravitational force.
July 30, 2015

Statistics
Since you probably want to run equipment that will only work withing a specified voltage range, you want range. For example if your motor requires a voltage between 90 and 110 it does not do much good to say the median is 100 if it burns out at 80 or 120
July 30, 2015

algebra
time to get there = d/60 time to get back = d/30 so d/60 + d/30 = 9 3 d/60 = 9 d = 3 * 60
July 30, 2015

alg
just did that above
July 30, 2015

whoops, sorry
carol drove for 3.5 hours d = 30*3.5 = 105 miles mother drove 105 miles in 3 hours 105 = r(3) r == 35 so yes a
July 30, 2015

Easy Math??
carol drives for 3 hours d = r t d = 30 * 3 = 90 miles mother drove 90 miles in 2.5 hours 90 = r (2.5) t = 36 miles/hour
July 30, 2015

Maths
3 is also a typo mess
July 30, 2015

Maths
I do not understand the first question I assume question 2 is a typo. If u = v then the angle is 0 u dot v = |u| |v| cos theta u dot v = 2*2 + 2*2 = 8 |u| = sqrt(4+4) = 2 sqrt 2 |v| = 2 sqrt 2 also (you put in the right values) 8 = 8 cos theta = 8 * 1 cos zero = 1
July 30, 2015

witbank high
the base is square so 5 * 5
July 30, 2015

algebra
I guess you probably mean y = -7/ (x^2-4) if x = 0 , y = -7/-4 if x = 1 , y = -7/-3 if x = -1, y = -7/-3 if x = 2, y = -7/0 if x = -2 y = -7/0 if x = 3, y = -7/5 if x = -3, y = -7/5 same left and right of x = 0 :)
July 30, 2015

Science
1000*9.81 + 1000*1 = 10810 N total mass = 1000 kg F = 1000*10 + 1000 * 1 = 11,000 N Ke on collision = m g h = m g (5) so (1/2) m v^2 = 5 m g v^2 = 10 g on rebound v^2 = 3.6 g sqrt (3.6/10) = sqrt .36 = sqrt (36/100) = 6/10 = 3/5
July 30, 2015

physics
v = Vi - 9.81 t 0 = Vi - 9.81*3 so Vi = 29.4 m/s m g h = (1/2) m v^2 so v^2 = 2(9.81) h 29.4^2 = 19.6 h h = 44.2 m
July 30, 2015

Easy Math??
He bought it for $80 As far ads I know the "par value" is of only academic interest. 100 * 6/80 = 7.5 %
July 29, 2015

Math
1) biggest side <12 because must stretch 6+6 so perimeter < 24 2) sum has to be 180 40+40 + 70 = 150 no but 40 + 70 + 70 = 180 ok 45+45 + 90 = 180 ok 100 + 100 too big so C is no good 60+60 + 90 = 180 ok 3) make a table 1 to 10 across 1 to 10 down start to fill it in ...
July 29, 2015

Maths
4! = 4*3*2*1 = 24 actually the order matters so it is permutations not combinations (google permutations and combinations) n! where the ! means "factorial" n! = n (n-1)(n-2) ....... (1) 5! = 5*4! = 5 * 24 = 120 or if you already know the 24 for four of them, then if ...
July 29, 2015

Science
Vi = 72,000 meters/3600 seconds = 20 m/s v = Vi + a t what is a ? a = F/m F = -m g (.5) so a = -.5 g = -9.81/2 = -4.9 close enough v = 20 - 4.9 t when v = 0 0 = 20 - 4.9 t so t is about 4 seconds average speed during stop = 20/2 = 10 m/s so d = 10 m/s * 4 s = 40 meters ( ...
July 29, 2015

Calculus
700 sin 23 = 273.51 = x speed (east) 700 cos 23 = 644.35 = y speed (north) If x = 333.51 and y = 644.35 then resultant = sqrt (x^2+y^2) and for angle east of north tan angle = x/y
July 29, 2015

College Algebra
well, I suppose I will try although really I am sure you could try first. 9 e^-(.012*49) = 9/(e^.588) = 9/1.8 = 5
July 29, 2015

physics
push force forward = 300 cos 30 = 260 N push force down = 300 sin 30 = 150 N normal force = 100*9.81 + 150 = 1131 N static maximum friction = 1131*.5 = 565 N so it does not budge and we need an older stronger woman or you have typos. It is unlikely that u static and u kinetic ...
July 29, 2015

physics
u = 11.3 cos 60 forever Vi = 11.3 sin 60 v = 11.3 sin 60 - 9.8 t v = 0 at top so at top t = 11.3 sin 60 /9.8 and also at top h = 49 + Vi t - 4.9 t^2 now at h = 0 0 = 49 + Vi t - 4.9 t^2 solve quadratic for t when h = 0 then that is time in air range = u t
July 28, 2015

physics
If it is thrown horizontal, the horizontal speed u remains 5 m/s until it stops. u = 5 v = - g t h = 19.6 - .5 g t^2 or 0 = 19.6 - 4.9 t^2 t^2 = 19.6/4.9 t = 2 seconds in air u = 5 v = -9.8 * 2 = -19.6 m/s so speed at ground = sqrt (25 +19.6^2 ) tan angle below horizontal = 19...
July 28, 2015

Physics
http://www.jiskha.com/display.cgi?id=1438108230
July 28, 2015

Physics
I just answered this below and you mean 30 degrees
July 28, 2015

Math
I would say that y = x - 8 then I would say -3x - 2(x-8) = 16 I would solve that for x and use that x to go back and find y
July 28, 2015

Physics
3.9/2 = 1.95 left of pivot --- right of pivot 50(1.95) = 27 x + 35(1.95) 27 x = 15(1.95) x = 15(1.95)/27 to the right of pivot
July 28, 2015

Physics
Original ke = (1/2)I omega^2 + (1/2)m v^2 omega = v/r = 35/r ke=(1/2)(2/5)mr^2(35^2)/r^2+(1/2)m (35)^2 = (1/2)m [(2/5)+1](35)^2 = (1/2) m (1.4)(35)^2 distance up = h = L sin 20 = L/2 potential energy stopped at top = original ke m g h = m g L/2 = (1/2)m(1.4)(35)^2 note m ...
July 28, 2015

Physics
.28 F = 98
July 28, 2015

Algebra
maybe you mean 5^4 - (8x)^2 = 0 ?????? that would be 25^2 - (8x)^2 =0 (25 - 8x)(25+8x) = 0 8x = 25 or 8x = -25
July 27, 2015

pre-calculus
112.5 = 90 + 22.5 ah ha, 22.5 is half of 45 we will be able to do this with half angle formulas first: sin 122.5 = sin(90+22.5) = sin 90 cos 22.5 + cos 90 sin 22.5 = cos 22.5 + 0 so we want cos (45/2) cos 45/2 = sqrt[ (1+cos 45)/2] = sqrt [ (1 +1/sqrt2)/2 } = sqrt [ (1 + sqrt ...
July 27, 2015

Integral calculus
h^2 = 2 x^2 2 h dh/dx = 4 x dh/dx = 2 x/h dh/dt = dh/dx * dx/dt = 2 (x/h) dx/dt but x/h = 1/sqrt 2 so dh/dt = sqrt 2 * dx/dt ---------------------- but more simply h = x sqrt 2 dh/dx = sqrt 2
July 25, 2015

Physics
total contact area = 4 * .217 * .179 = .155 meters^2 total force = gage pressure * area = 176357*.155 = 27,401 Newtons weight It might be interesting to also find the mass in kilograms assuming this all happens on earth 27,401/9.81 = 2793 Kg mass (heavy car)
July 24, 2015

Math
whoops (x+5)(x-2) (y^3+5)(y^3-2)
July 23, 2015

Math
I personally would say x = y^3 then it is x^2 + 3 x - 10 (x-5)(x+2) now go back (x^3-5)(x^3+2)
July 23, 2015

calculus
obviously 2 r </= 12 volume = pi r^2 h =1000 then pi r^2 = 1000/h but h</= 11 so pi r^2 >/= 1000/11
July 22, 2015

Physics
http://www.mathpages.com/home/kmath114/kmath114.htm u + 2 U
July 22, 2015

Math
find how many minutes until one is left. That one leaves immediately if the first ones left at t = 0 a(n+1) = (1/2)A(n) a(1) = 256 a(N) = 1 an = a1 r^n-1 1 = 256 *.5^(n-1) .5^(n-1) = 1/256 (n-1) log .5 = log (1/256) n-1 = 8 n = 9 so 9 * 5 min = 45 min if the first ones left at...
July 22, 2015

Physics
suspect you mean 30 south of west momentum east 7900*5 - 1650*20 cos 30 momentum south 1650*20 sin 30 new mass = 7900 + 1650 new mass*speed east = old momentum east new mass* speed south = old momentum south
July 22, 2015

Math Check
x^2+ x(6)^1/2+3=x^2 +3 makes no sense at all. 6^(1/2) is not zero
July 22, 2015

Physics
T = our unknown angle theta angular acceleration = alpha = d omega/dt I = (1/2) M R^2 FF = friction force up slope FF * R = torque so FF * R = (1/2) M R^2 * alpha FF = (1/2)M R alpha R omega = no slip velocity R alpha = no slip acceleration = a so FF = (1/2) M a F = m a F = M ...
July 21, 2015

Algebra1
of course we could have short cut that by saying 9 (x-8)^2 = y-8 then (x-8)^2 = (1/9)(y-8) but best do the whole completing the square process.
July 20, 2015

Algebra1
If it is indeed y = 9 (x-8)^2 + 8 then y = 9 (x^2 - 16 x + 64) + 8 y = 9 x^2 - 144 x + 576 + 8 y = 9 x^2 - 144 x + 584 then x^2 - 16 x + 64 8/9 = y/9 x^2 - 16 x = y/9 -64 -8/9 x^2 - 16 x + 64 = y/9 -64 -8/9 + 64 (x-8)^2 = y/9 -8/9 = (1/9)(y-8) vertex at (8,8)
July 20, 2015

not a parabola
Need an x^2 somewhere perhaps y = 9 (x-8)^2 + 8 or something?
July 20, 2015

math
3^2 * 6 = 9*6 = 54
July 20, 2015

math
area is proportional to scale squared volume is proportional to scale cubed
July 20, 2015

physics
10 = (1/2)(.4) t^2 solve for t v = 0 + .4 t
July 20, 2015

physics
v = 30 - a (75) assume you mean 1.5 km or 1500 meters 1500 = 30 (75) - .5 a (75)^2 solve for a then go back and get v at 75 seconds
July 20, 2015

physics(kinematics)
You are welcome. Actually that was fun :)
July 19, 2015

physics(kinematics)
me too :)
July 19, 2015

physics(kinematics)
we agree !
July 19, 2015

physics(kinematics)
v = Vi - 8 t x = Xi + Vi t - 4 t^2 20 = Xi + Vi (4) - 4(16) 20 = Xi + 4 Vi - 64 Xi + 4 Vi = 84 so Vi = (84-Xi)/4 16 = Vi - 8 t 16 = (84-Xi)/4 - 8 t (eqn 1) 4 = Xi + [(84-Xi) /4] t - 4 t^2 (eqn 2) from eqn 1 64 = 84-Xi - 32 t so Xi + 32 t = 20 Xi = (20 - 32 t) substitute that ...
July 19, 2015

college chem
Na ---- 23 g/mol Cl ---- 35.5 g/mol so NaCl 58.5 g/mol so 42.6/58.5 = .728 mols .728/1.58 = .461 mol/Liter
July 19, 2015

how exasperating !
Oh my :(
July 19, 2015

calculus
sketch it of course where does y = 2x hit y=6/x? 2 x = 6/x x^2 = 3 x = sqrt 3 then y = 2 sqrt 3 so from x = 0 to x = sqrt 3 integrate y = (2 x-.5 x) = 1.5 x 1.5 x^2/2 .75 ( 3-0) = 2.25 then where does y = .5 x hit y = 6/x? .5 = 6/x^2 x^2 = 12 x = 2 sqrt 3 so integrate y = (6/x...
July 19, 2015

Physics
.... and if you have a physics question type PHYSICS, not Blue bells....,
July 19, 2015

blue bells model school
The momentum does not change but the balls are together during the collision so initial ke = (1/2) m V1^2 = total energy initial momentum = m V1 final momentum = (n+1)m V2 so V2 = V1/(n+1) so ke during collision = (1/2) (n+1)m V2^2 = (1/2) (n+1)m V1^2/(n+1)^2 = (1/2)m V1^2/(n+...
July 19, 2015

Thokozwayo secondary school
So I can talk to my neighbors.
July 19, 2015

Physics
Jai showed you how to do this type of problem below. All your problems are really the same and are solved the same way. In other words if you do what Jai said, you can do them all. We are not here to do them all for you. http://www.jiskha.com/display.cgi?id=1437267116
July 19, 2015

math
DRAW IT ON A GRAPH ! square in quadant 3 or 4 diagonals hit at (2,-2) or (-2,-2) that is a and d NOT B or C
July 18, 2015

math
+1 -2 +3 -4 +5 .....+99 -100 = +1 +3 +5...... +99 -2 -4 -6...... -100 --------------------- ADD -1 -1 -1 ..... -1 :) LOOKS LIKE AROUND -50
July 18, 2015

math
you left the lower limit out so I assume 0 sum of all integers from -9 to +9 looks like zero to me so 4 pm
July 18, 2015

Algebra
LOL - thanks
July 18, 2015

Algebra
The key is "rounded to 82" :)
July 18, 2015

Algebra
Well, try 49 :) 49 +4*90 = 409 409/5 = 81.8 rounds to 82 so ok try 48 48 +4*90 = 408 408/5 = 81.6 rounds to 82 so ok try 47 47 + 4*90 = 407 407/5 = 81.4 no good
July 18, 2015

Algebra
( a+b+c+d+e)/5 = 82 a+b+c+d+e = 410 but 90*4 = 360 so he got at least 50
July 18, 2015

math
500/9 = 55.5 so there are 55 from 9 to 495 j = 55 500/7 = 71.4 so there are 71 from 7 to 497 k = 71
July 18, 2015

Math 115 Statistics
draw a box or matrix with your 36 possibilities make an x for win, an o for lose(3,4,6) 0 1 2 3 4 5 6 1 x o o x o x 2 o o x o x x 3 o x o x x x 4 x o x x x x 5 o x the rest x 6 number of o s = 10 so 10/36
July 18, 2015

Math URGENT!!!
10/30 * 9/29 * 8/28
July 18, 2015

calculus
dM/dt = -k M separate variables, M left, t right dM/M = -k dt integrate ln M = -k t + c note e^log a = a ao e^ln M = M = e^(-kt+c) = e^-kt e^c or since e^c is some constant call it C M = C e^-kt note that when t = 0 e^-kt = 1 so C = initial amount so here M = 100 e^-kt
July 17, 2015

physics
good answer.
July 17, 2015

maths
f-5 = 3(s-5) f + 10 = 2(s+10) ---------------- -15 = 3(s-5) - 2(s+10) -15 = 3s - 15 -2s -20 20 = s then f-5 = 60 -15 f = 50
July 16, 2015

geometry
(8/6)(12+12+6)
July 16, 2015

geometry
Pure luck ! You are welcome :)
July 16, 2015

geometry
ah, I think 155 / C
July 16, 2015

calculus
dT/dt = -k (T-38) try dT/(T-38) = -k dt ln(T-38) = -k t T-38 = ce^-kt T = 38 + ce^-kt when t = 0, T =75 75 = 38 + c c = 37 so T = 38 + 37 e^-kt at t = 30 , T = 60 so 60 = 38 + 37 e^-30 k 22/37 = .595 = e^-30 k ln .595 = -.52 = -30 k so k = .0173 and T = 38 + 37 e^-.0173 t you ...
July 16, 2015

Alebra 2
law of cosines c^2 = a^2 + b^2 - 2 a b cos angle
July 16, 2015

Stats
first pick p anchovies = 1/12 p not anchovies = 11/12 second pick you now only have 11 toppings one of which is anchovies p anchovies = 1/11 p not anchovies = 10/11 11*10/(11*12) = 10/12 = 5/6 p neither anchovies =
July 16, 2015

Math
We want y = m x + b ? solve for y 3 y = 2 x - 6 so y = (2/3) x -2 so m = 2/3 , b = -2
July 16, 2015

Math
slope = 4162 but when t = 10, n = 45400 so n - 45400 = 4162 (t-10) ----------------------------- n at t = 19 n = 45400 + 4162(9)
July 16, 2015

Math
slope = slope (y-9)/(x-1) = (19-9)/(3-1) = 5 you can do the rest
July 16, 2015

Math
12 y = 15 x - 1 y = (15/12) x - 1/12 y = (5/4)x - 1/12
July 16, 2015

Geometry
180-45
July 16, 2015

Physics
If Fx is on a graph, you need the area under the curve from x = 0 to x = 3
July 15, 2015

Physics
work done = integral Fx dx from 0 to 3 calculate that then Ke final = Ke initial + work done
July 15, 2015

Physics
assume you mean dot or scalar product A dot B = |A| |B| cos theta so here cos theta = .5 cos^-1 0.5 = 60 degrees
July 15, 2015

Calculus Partial Derivatives
x y z = k sum = s = x + y + z ds = ds/dx dx + ds/dy dy + ds/dz dz = 0 for max or min but ds/dx = ds/dy = ds/dz = 1 so ds = dx + dy + dz = 0 so max when dx = -dy - dz but x = k/(yz) dx/dy = -kz /(yz)^2 dx/dz = -ky /(yz)^2 so dx = -[-kz/((yz)^2 ]dy - [-ky/(yz)^2]dz so k y = k z ...
July 15, 2015

precalc
well, if you are not allowed to use calculus you must complete the square to find the vertex of that parabola. 16 t^2 - 48 t -20 = -h t^2 - 3 t - 1.25 = -h/16 t^2 - 3 t = -h/16 + 1.25 t^2 - 3 t + 9/4 = -h/16 + 3.5 (t - 1.5)^2 = - 1/16 ( h - 56) so at peak t = 1.5 and h = 56...
July 12, 2015

sjrkps
By the way, if you post a physics question say physics, not sjrkps so you get a physicist.
July 12, 2015

sjrkps
v = Vi + a t v = 0 + .8 m/s^2 * 20 s = 16 m/s
July 12, 2015

math
but much more fun my way :)
July 12, 2015

math
x^2 = tan^2 +2 tan sin + sin^2 y^2 = tan^2 -2 tan sin + sin^2 x^2-y^2 = 4 tan sin = 4 sin^2/cos ____________________________________ x y = tan^2 -sin^2 = sin^2/cos^2 -sin^2 = sin^2/cos^2 - sin^2 cos^2/cos^2 = [sin^2 / cos^2] [1-cos^2] but 1 - cos^2 = sin^2 so = sin^4/cos^2 so ...
July 12, 2015

physics
weight = 320+ 4*15 + 500 + 750 + 1000 = total force up moments around one end Ff=force up from floor at far end Fn = force up at near end 320(1.2)-Fn*.3+30*.3+500*.4+750*1.2 +1000*2 +30*2.1-Ff*2.1 = 0 but Fn = (total force up - Ff)
July 12, 2015

Physics
V = Vi e^-(t/RC) .1 = e^-(10/10C) = e^-(1/C) ln .1 = -1/C
July 11, 2015

Physics
but the boat is also being pushed by the propeller m = 60 + 500 = 560 kg
July 11, 2015

physics
You are welcome.
July 11, 2015

physics
6000 Pascals is 6000 Newtons per square meter. Multiply that by the area of the wall in square meters to get the force in Newtons. The density of water is about 1000 kg /m^3 so the weight of a cubic meter of water is about m g = 1000 * 9.81 = 9810 Newtons so a column of water ...
July 11, 2015

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