Tuesday
August 30, 2016

Posts by Damon

Total # Posts: 26,839

Calculus
well, any old plane that is not parallel to the other two will intersect both at a point along the lines of intersection of those planes. The line of intersection will be parallel to the cross product of or two normals i j k 1 1 3 1-1 2 Find a plane that has that line of ...
July 8, 2016

Got to be kidding
Due to bending in a beam? Due to weight of mass hanging from ceiling by string? Due to compression sound wave in steel bar? Due to cooling of same bar while ends are fixed? etc etc etc etc ........
July 7, 2016

Physics
force = m g = 8 (9.81) work = potential energy gained = m g h = 8 (9.81)(12) power = work/time = 8 (9.81)(12)/15 If for some incomprehensible reason you really ant power/force, divide 12/15
July 7, 2016

Maths
amount = original * (1+r)^t 3 = (1+r)^t ln 3 = t ln (1+r) t = ln 3 / ln(1+r) r = .09 t = ln 3 / ln(1.09) t = 1.0986 / .086178 t = 12.74 years ====================== check 3 = 1 * 1.09^12.74 ?????? 3 = 2.997 yes that will do
July 7, 2016

Physics
u = horizontal speed = 73/3 = 24.3 m/s falls 8 meters in 3 seconds h = Hi + Vi t - 4.9 t^2 0 = 8 + 3 Vi - 9(4.9) Vi = 12 m/s upward speed at tree top of 8 m so let's find the top above that tree v = Vi -9.81 t 0 = 12 - 9.81 t t = 1.22 seconds rising above tree so h at top ...
July 5, 2016

Physics
find ke before child jumps (1/2)I omega^2 find new I (which you did already) find new omega (which you did already) Find new ke = (1/2) Inew (omega new)^2 now work done = new ke - old ke I went up a little but omega went down so I suspect the work will be negative In other ...
July 5, 2016

been there, done that
http://www.jiskha.com/display.cgi?id=1467694862
July 5, 2016

Physics
p = m v Ke = (1/2) m v^2
July 5, 2016

Physics
Force * time = change of momentum T (7*10^-4) = 2 * 6
July 5, 2016

Physics
impulse = change of momentum = force * time
July 5, 2016

Physics
Power * time = change in energy 20 P = m g h = 1800 * 9.81 * 15
July 5, 2016

Physics
(1/2) m v^2 = m g (45-5) v^2 = 2 (9.81)(40) --------------------------------- Second question has no real answer unless we assume that the potential energy is zero at the ground level. ONLY changes in potential have meaning,and you must always define a base If we ASSUME U = 0 ...
July 5, 2016

Physics
Maybe assume they both take the same time to stop when they crash into you Force * time = change in momentum for duck Force * time = 2.8 * .35 for goose Force * time = 3.4 * .75
July 5, 2016

Prealgebra/probability
tails, tails, heads does NOT work H H T H T H T H H Quarter, Penny could be H H H T T H T T that is four, 8 now for each so 32 so I agree
July 3, 2016

physics
add up the forces. That is one equation add up the torques (moments) about x = 0. That is the second equation
July 3, 2016

physics
C + W = 926 so 2 W = 1852 - 2 C then (1852 - 2 C) + .6 C = 736 1852 - 736 = 1.4 C etc
July 3, 2016

physics
190 down at left C up at x = .6 75*9.81 down at x = 1 W up at x = 2 forces up = forces down C + W = 190 + 75*9.81 = 926 Newtons moments about x = 0 sum to 0 -.6 C + 75*9.81*1 - 2 W = 0 or 2W +.6C = 736 Newton meters
July 3, 2016

Physics
lol, finally 33 * 50 = 12 x x = 33 * 50/12
July 3, 2016

Physics
so where is the fulcrum?
July 3, 2016

LOL - not enough known
I do not know either mass or the x of the right hand side
July 3, 2016

Physics
v = Vi + a t 0 = 30 + a (6) a = -5 m/s^2 ==================== v = Vi - 5 t 0 = 40 - 5 t t = 8 seconds
July 3, 2016

physics
work = force * distance so how far? assume v =0 at start F = m a 4 = 20 a a = (1/5) m/s^2 v = Vi + a t v = 0 + 3 a x = Xi + Vi t + (1/2) a t^2 x = 0 + 0 + (1/2)(9) x = 4.5 meters so W = F x = 4 * 4.5 = 18 Joules
July 3, 2016

math
2 (L+w) = 270 L + .75 L = 135 1.75 L = 135 L = 135/1.75 etc
July 3, 2016

math
a + 3 a = 80 so 4 a = 80 a = 20 etc
July 3, 2016

Math
b = (5/8) s so g = (3/8) s now g = (3/8) s + 6 and number of students = s + 6 b = 5/8 s = (3/8)s +6 so (2/8)s = 6 s = 24 that was original s s+6 = new total = 30
July 3, 2016

better
http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/atomic/covalentrev4.shtml
July 3, 2016

CHEMISTRY
http://search.yahoo.com/yhs/search?p=dot+and+cross+diagram+H2O+bond&ei=UTF-8&hspart=mozilla&hsimp=yhs-001
July 3, 2016

Physics
find resultant and do the opposite. north 11 + 22 sin 30 east 22 cos 30 magnitude = sqrt(north^2 + east^2) tan angle north of east = north/east you want that magnitude but opposite direction, same angle south of west
July 2, 2016

PHYSICS
vol = 20 cm^3 ????? Your typing is very confusing then upward force = weight of water displaced (Archimedes) = 10 cm^3 * 1 gram/cm3 * g = 10 grams * g = .010 kg * 9.81 = .098 Newtons upward buoyancy but weight = volume * density * g = 20 * 2.5 * 9.81/1000 = 0.49 N difference...
July 2, 2016

Math
no if she made 65 out of 100 that will take less than if she made 650 out of 1000
July 2, 2016

Physics
(1/2) m v2^2 = 1.23 (1/2) m v1^2 so v2 = sqrt(1.23) v1 v2 = 1.11 v1 well, that is an 11% increase
July 2, 2016

Mathematics
25 letters allowed for first spot 25 for second spot so 625 letter combinations 9 digits 9*9*9*9 = 9^4 so 625*9^4 = 4,100,625
July 2, 2016

physics
or to do it the physics way: (4585 drops/ft^2)*(1 ft^2/15 tiles) = (4585 drops/ 15 tiles)
July 2, 2016

physics
4585/15
July 2, 2016

patel
must be bigger than 1 because 1^2 = 1 must be smaller than 2 because 2^2 = 4 so between 1 and 2 by the way sqrt 3 = 1.732050808 approximately
July 2, 2016

Sciencr
Yes, hot air holds more water. Fog happens if air saturated with all the moisture it can hold cools down. Similarly if saturated air comes in contact with a cool surface like a basement wall that air cools and the water condenses out. Interestingly by the way, hot water holds ...
July 2, 2016

physics
Are you sure the captain is a novice? Despite the fact that he will land downstream from his starting point, his fastest path across the water is to head straight across. Anyway I will pretend I am not a navigator and do what your book wants you to do. For example: He could be...
July 2, 2016

gibberish
please check what you wrote "Earth is 2R times far away from earth " makes no sense to me.
July 2, 2016

physics
force 1215 m what is that about? Anyway all that matters is depth p = rho g h = 1000 kg/m^3 * 9.81 * 3 = about 30,000 Pascals that is the pressure abouve the one atmosphere at the surface or "gage" pressure. That one atmosphere is about 100,000 Pascals so the total ...
July 2, 2016

Math(Assignment Due
http://davidmlane.com/hyperstat/z_table.html
June 29, 2016

Math(Assignment Due
Google David Lane normal distribution
June 29, 2016

Math
6*5*4*3= 30*12 = 360
June 29, 2016

Math1
165 * 1.04
June 28, 2016

Calculus
x^2 dy+2xydx - 2ydy +(1/xy)(xdy+ydx) = 0 [x^2-2y+1/y]dy + [2xy+1/x]dx = 0 dy/dx = -[2xy+1/x] / [x^2-2y+1/y]
June 28, 2016

Math
small left ---> large right 5467
June 28, 2016

Probability and statistic
http://davidmlane.com/hyperstat/z_table.html
June 27, 2016

physics
60,000 /3600 = 16.7 m/s 45,000 /3600 = 12.5 m/s v =Vi + a t 12.5 = 16.7 + 10 a a = -0.42 meters/second^2
June 27, 2016

physics
d = (1/2) a t^2
June 27, 2016

Math
in the slope/intercept form: y = m x + b m is the slope b is the y axis intercept where x = 0 here the slope is positive 0.5 so the line goes up to the right from the point (0,-2) (and of course down to the left :)
June 27, 2016

Math
y = 35 + 15 x
June 27, 2016

maths
(x-3)(3x+2)=0 alpha = 3 beta = -2/3 so (x-9)(x-4/9) = y x^2 -9x -4x/9 + 4 = y y = x^2 - (85/9) x + 4
June 27, 2016

English
One says "at". I suppose if you live in a tunnel, you eat "in" it :) However is you say: "What about dinner in my house?", You probably mean instead of in my yard or garage.
June 26, 2016

GEOMETRY
p(a)+ p (b) - p(a and b) 1,2,3,or 4 out of 6 = 4/6 tail = 1/2 = 3/6 4/6 + 3/6 - 2/6 = 5/6
June 26, 2016

GEOMETRY
prob of first one blue = 5/16 now we have 15 in the bag prob of white = 5/15 = 1/3 so 5/16 * 1/3 = 5/39
June 26, 2016

GEOMETRY
Hey, it is time you should be able to do these.
June 26, 2016

GEOMETRY
A and B could be 6 A and C - impossible B and C - impossible
June 26, 2016

GEOMETRY
the attempts are independent so (3/7)^3
June 26, 2016

GEOMETRY
2 out of 15 2/15
June 26, 2016

GEOMETRY
1/16
June 26, 2016

math
18,000 * 1.07^18
June 26, 2016

GEOMETRY
p even = 3/6 = 1/2 p A = 1/3 they are independent so 1/2 * 1/3 = 1/6
June 26, 2016

Math
cos T * sin T = 1/4 so 2 cos T * sin T = 1/2 so sin 2 T = 1/2 thus 2 T = 30 deg or pi/6 radians T = pi/12 radians or 15 deg now cos * sin must be + so T in quadrant 1 or quadrant 3 so actually T = pi/12 or T = 13pi/12 which is 195 deg pi/12 + 13 pi/12 + (2pi+pi/12) = (1/12 +13...
June 26, 2016

Biology
http://shenndesigns.weebly.com/my-physical-trait---curly-hair.html half of each assuming no one has only a little curly so 4:4
June 26, 2016

maths
a b a + b = 9 a = (1/2) b ============================== (1/2) b + b = 9 so (3/2) b = 9 so b = 18/3 which is 6 which means a = 3 and a b is 36
June 26, 2016

math
3 of anything + 3 of the same thing = 6 of them 6/30 = 1/5
June 26, 2016

Science
.05 * 90 = 4.5 mL
June 26, 2016

math - incomplete problem statement
(L+3)(w+3) = 84 + L w L w + 3 L + 3 w + 9 = 84 + L w 3 L + 3 w = 75 need another piece of information to solve Suspect you were given how much longer it was than wide
June 25, 2016

Physics
time t at 80 time t at 40 80 t + 40 t = 60 120 t = 60 t = (1/2) hour at each speed distance = 80(1/2) + 40(1/2) = 60km av speed = 60 km/1 hour
June 25, 2016

physics
north = 400 - 400 = 0 west = 300 d = sqrt (0^2 + 300^2) = 300 I have a hunch you have a typo.
June 25, 2016

Physics
capacitance is charge per unit voltage 60/40=1.5 Farads
June 25, 2016

Maths Year 10
x = k - 5 k x = k(k-5) = k^2 - 5k
June 25, 2016

math
54 = 15 + 3.25 x
June 25, 2016

Science
Will all that NaCl dissolve? I suspect not.
June 25, 2016

math
12 - 3 = 9 21 - 12 = 9 hmmm x - 21 = 9 maybe or x = 30 etc
June 25, 2016

Mathematics
a - (2/5)a = 24 3a/5 = 24 a/5 = 8 a = 40 yes
June 25, 2016

CHEMISTRY
NO-3 ? , SO2-4 ?, PO3 -4 Where did you get these strange charges for the ions? eg PO3 normally -3 ASSUMING your strange valences: In +3 NO -3 then to be neutral InNO In+3 * 4 = +12 SO2-4 * 3 = -12 so In4(SO2)3 similarly In4 (PO3)4 But I suspect you have the original statement ...
June 24, 2016

trig
north = -3*14+2*14*cos 60 east = 2*14*sin 60 d^2 = north^2 + east^2
June 24, 2016

Math: PreCal
yes, amplitude is five and period is 3 pi when x = 0: y = 5 cos (-pi/6) = 5 (.866) that is not a max or a min or and x intercept However there is always a reflection about the points where the argument of the cos function is zero because cos -z = cos z that is when (4/6)x = pi...
June 24, 2016

physics
some point (0,y) on y axis between y = -3 and y = +6 field up = k(-12)/(6-y)^2 field down = k(-5)/(y-3)^2 so 12(y-3)^2 = 5(6-y)^2
June 22, 2016

physics
find the linear velocity of the car from v = a t then angular velocity = v/R
June 21, 2016

maths
Ah, there, on a new computer that would not let me post link unless I typed my Jiska name in :)
June 21, 2016

maths
http://www.mathsisfun.com/numbers/dividing-by-zero.html
June 21, 2016

English
4-1 and 4-2 are correct although 4-2 is unlikely. 4. and 4-3 are incorrect.
June 21, 2016

whoops, forgot what I did before
I mean a = (F/m)e^-(bt/m)
June 19, 2016

physic mechanic
Friction force, unlike gravitational or electrostatic is not directed toward a source like a center of mass or a charge. Friction is therefore not a central force. Did you get your earlier one about a = F/m (1- e^(bt/m) ) alright?
June 19, 2016

algebra
each year value = 0.92 value year before v = Vi (0.92)^n v = 25,000 (0.92)^6
June 19, 2016

Scient
a mL of water is a gram 4.5 / x = .09 x = 50 grams water remains so 450 grams evaporated
June 18, 2016

Physics
7 m * 2 v = 14 m v (1/2)(7m)(2v)^2 = (1/2)(7)(4) mv^2 = 28 * (1/2)m v^2
June 18, 2016

Physics (Normal force and static coefficient)
F down slope = m g sin 42 = 2 * 9.8 * sin 42 = 13.1 Newtons down the slope so 13.1 = mu m g cos 42 or sin 42 = mu cos 42 mu = tan 42 mu = 0.900 At least 0.900 could be more
June 18, 2016

Maths
J = A - 15 J+10 = (1/2)(A+10) A - 15 + 10 = A/2 + 5 A/2 = 10 A = 20 J = 5 ========== check 2(5+10) = 20+10 30 = 30 sure enough
June 18, 2016

Math
In quad 2 sin is + cos is - of course we can look up the angle knowing the tangent and then find the sin etc but that is too easy. tan T = -5 = sin T/cos T cos T = sqrt (1 - sin^2 T) so -5 = sin T / sqrt(1-sin^2 T) 25 (1-sin^2 T ) = sin^2 T 25 = 26 sin^2 T sin^2 T = 25/26 sin ...
June 17, 2016

Geo Quiz
No way you could help the guy below you, Momen, who asked a far more difficult question luckily answered by Bob Pursley elsewhere.
June 17, 2016

Geo Quiz
All of your choices are nonsense the way you typed them without parentheses (x+3)^2 + (y-6)^2 = 25
June 17, 2016

Geo Final
surface area is 6 times area of one face = 6 (9) = 54
June 17, 2016

social studies.
You do not need help. You are doing just fine. For number four I might say the poor unemployed people of the country rather than the Republic itself.
June 17, 2016

Calculus
If you use right endpoints for the height of each rectangle, Bob has it I think and the answer would be 8. If you use trapezoids you get a more accurate answer, 9 , but they asked for the inaccurate answer.
June 17, 2016

CALCULUS
well, try this backwards assuming you answered correctly y = -4 cos [ ln(6x) ] dy/dx = -4 (-sin [ln(6x)]*6/6x = 4 sin [ln(6x)] / x I see nothing wrong with your answer.
June 16, 2016

geometry
(x+3) / (3x-1) = 1/2 2 x + 6 = 3 x - 1 x = 7 GR = 3(7) - 1 = 20
June 16, 2016

Math
subtract 3 t from both sides 2 c = 35 - 3 t divide both sides by 2 c = (35/2) - (3/2) t or c = 17.5 - 1.5 t
June 14, 2016

Math
well, they all amount to the same thing. add -2 x + 5 to both sides 4 x - 2 x = 9 + 5 2 x = 14 x = 7
June 14, 2016

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