Sunday

May 1, 2016
Total # Posts: 26,126

**physics & math**

sqrt ( 2*1.6*10) = 4 sqrt 2 = 5.66 m/s
*February 6, 2016*

**typos**

You mean g = - 32 ft/s^2 so h = Hi + Vi t + (1/2)a t^2 h = 105 - 9 t - 16 t^2 at ground: 0 = 105 - 9 t - 16 t^2 or 16 t^2 + 9 t - 105 = 0 t = [ -9 +/- sqrt(81+6720)]/32 t = [-9 +/- 82.5 ]/32 use positive time 2.30 seconds
*February 5, 2016*

**Physics**

V= i R 2 = .1 R and 2 = 5 R
*February 4, 2016*

**Physics help**

well electrostatic force causes hair to stand on end and gravity keeps the planets in orbit by the way
*February 4, 2016*

**Physics PLEASE PLEASE HELP! CONFUSED**

do vertical and horizontal problems separately Vertical Just plain fall, no initial velocity up or down so a) 10 = (1/2)(9.81) t^2 b) use that t to find out how far away he landed d = u t = 1.2 t c) vertical v = g t = 9.81 t horizontal u = 1.2 speed = sqrt (u^2+v^2) direction ...
*February 3, 2016*

**physics**

again that d is the part in the heavy liquid for the water depth use L-d
*February 3, 2016*

**physics**

B) rhoL L^2 d + rhoW L^2 (L-d) = rhoB L^3
*February 3, 2016*

**physics**

Force up on block = rhoL *L * L * d * g where d is the draft or distance submerged that has to equal the weight of the block which is rhoB L^3 g so rhoB L^3 g = rhoL L^2 d g d = (rhoB/rhoL) L d/L = rhoB/rhoL but we want (L-d)/L which is 1 - d/L 1 - d/L = fraction above = 1-...
*February 3, 2016*

**True & False explanations Physics**

When a projectile is fired at 45 deg. angle and is in free fall, the only point along the path that the acceleration of the object is zero is the instant when the object is at the highest point of its path. Answer: False Can someone explain how? ============================== ...
*February 3, 2016*

**physics**

v = Vi - g t v = 20 - 9.81(2) h = Vi t - 4.9 t^2 h = 20(2) - 4.9 (4)
*February 3, 2016*

**One Last Queston**

My vote is for A Nothing slows it down
*February 2, 2016*

**differential equations**

for purposes of integration n k m are constant then ds/dt = -ks (s^2/nm - S/n -s/m +1) = -k [ s^3/nm - s^2/n - s^2/m + s] =k[ -s^4/4nm +s^3/3n + s^3/3m -s^2/2 + c] You can play with this perhaps http://www.wolframalpha.com/input/?lk=3&i=plot++-s^4%2F4n+%2Bs^3%2F3n+%2B+s^3%2F3...
*February 2, 2016*

**Physics**

so weight = 4.11*9.81 = 40.3 N down Tension = 23.5 N up 23.5 - 40.3 = 4.11 a a = - 4.09 m/s^2 so a is down, weight wins
*February 2, 2016*

**but what about the weight?**

weight = m g = 4.11 * 9.81 Newtons
*February 2, 2016*

**Math**

V = pi r^2 h
*February 2, 2016*

**maths**

5/35 = x/21 x = 21 * 5 / 35
*February 2, 2016*

**Algebra**

I think you have typos but perhaps .75 x = 30
*February 2, 2016*

**Algebra**

in pennies: 4500 + 29.5 m = 9000 + 7 m 22.5 m = 4500 m = 200 miles
*February 2, 2016*

**math**

approximately 40828.19332
*February 2, 2016*

**Math**

56 * 4 = 224
*February 2, 2016*

**US History**

LOL - that was a media generated war ! It was the very origin of the term: "yellow journalism" starting with the explosion of the Battle ship Maine which seems to have been an engineering error but the press blamed on the Spanish. See: http://history.state.gov/...
*February 2, 2016*

**Which war ?**

Civil war? Vietnam ? Iraq?
*February 2, 2016*

**algebra**

100 a + 75 s = 14000 pennies a+s = 150 so a = 150-s 100(150 - s) + 75 s = 14000 15000 - 25 s = 14000 1000 = 25 s s = 40 then a = 150 - 40 = 110
*February 2, 2016*

**algebra**

2 x + 3 y = 252 4 x + 1 y = 244 multiply second equation by 3 2 x + 3 y = 252 12x + 3 y = 732 -----------------subtract - 10 x = - 480 x = 48 then y = 244-192 = 52
*February 2, 2016*

**algebra**

number = 10 x + y x+y = 12 y = 2 x so x + 2 x = 12 x = 4 then y = 8 so 48
*February 2, 2016*

**algebra**

f+4 = 3 (s+4) f-6 = 7(s-6)
*February 2, 2016*

**math Chem formula wrong**

3 % C 10 % Ca 87 % O Like no way CaCO3 40 + 12 + 48 = 100 molar mass 40% Ca, 12% C , 48% O so the real answer is 400 g , 120 g 480 g BUT using your strange numbers: in 100 grams: .03 * 100 = 3 g .1 * 100 = 10 g .87 * 100 = 87 g
*February 2, 2016*

**Math**

That is high precision. For low I would pick 3*10^3
*February 1, 2016*

**Science**

I guess they stick together. 8*10 - 6*50 = (6+8) v -220 = 14 v v = -15.7 m/s
*February 1, 2016*

**Math**

F = k x 10 = k (.5) k = 20 lb/in 15 = 20 x x = 0.75 in
*January 31, 2016*

**mathematics**

(6^5 /6^3) + 7^0 ??? 6^2 + 1 37
*January 31, 2016*

**science**

50 v = .1(50) v = .1 m/s
*January 31, 2016*

**Science**

Those are VECTORS You need BOTH magnitude and direction to add them. The resultant could have any magnitude between 20 and 70 meters
*January 31, 2016*

**Science**

r and Re F = G Mm/r^2 = (.25) G Mm/Re^2 or .25/Re^2 =1/r^2 .25 r^2 = Re^2 .5 r = Re r = 2 Re height = 2Re-Re = Re
*January 31, 2016*

**physics**

h = Hi + Vi t - 4.9 t^2 0 = 29 - 8.95 t - 4.9 t^2 t = [8.95+/-sqrt(8.95^2 + 4*29*4.9)]/(2*4.9) t = [8.95 +/-25.46 ] /9.81 use + t 3.51 seconds
*January 31, 2016*

**physics**

v = 19 - 9.81 t at top v = 0 t = 19/9.81 = 1.94 seconds to top at top h = 0 + 19 t - 4.9 t^2 h = 18.4 m high at top the same as the rise time 1.94 s the same 19 m/s but down now
*January 31, 2016*

**physics**

v = 0 = 81 - 5 t 800 = 81 t - 5.2 t^2 use that same stopping time t
*January 31, 2016*

**physics**

I guess we are to do this all in feet and seconds? v = 205 mi/h *5280ft/mi*(1h/3600s)) = 301 ft/s a = 301/2.7 = 111 ft/s^2 d = (1/2)(111)(2.7)^2 =406 ft
*January 31, 2016*

**Physics**

9.7*3 + 7.6*0 = 9.7 Va + 7.6 Vb so Va = (29.1 -7.6Vb)/9.7 then .5(9.7)(9)= .5(9.7)Va^2+.5(7.6)Vb^2
*January 31, 2016*

**Physics**

if acceleration is constant their average speed during the stop = 10/2 = 5 m/s 5 m/s * 30 s = 150 meters
*January 30, 2016*

**math**

21/x = 7/10 ? multiply both sides by 10 x 21 * (10 * x)/x = 7 * (10 * x)/10 210 = 7 x x = 210/7
*January 30, 2016*

**Science**

Yes, the answer is c
*January 30, 2016*

**Math**

2 y + 6 + 4 y =
*January 29, 2016*

**MATHS**

x + (5x-7) = 59 6x = 66 x = 11 and 5x - 7 = 55-7 = 48
*January 29, 2016*

**math**

(9 miles/ hour )(2 hours) = 18 miles note that the hours canceled top and bottom
*January 29, 2016*

**Math**

Hey- you can do that ! x-2 = 0 so x = 2 x-3 = 0 so x = 3 x+3 = 0 so x = -3
*January 29, 2016*

**Algebra 2**

boring ! x-4y-6z=-34 times 5 -7x+5y-7z=-24 times 4 +5 x -20 y - 30 z = -170 -28x +20 y - 28 z = -96 --------------------------add -23 x + 0 -58 z = - 266 now the last 2 -7x+5y-7z=-24 times 7 +5x-7y-1z=-18 times 5 -49 x + 35 y - 49 z = -168 +25 x - 35 y - 5 z = -90...
*January 29, 2016*

**Algebra 2**

http://www.gregthatcher.com/Mathematics/GaussJordan.aspx I get (4, 5, 3)
*January 29, 2016*

**Algebra 2**

http://www.gregthatcher.com/Mathematics/GaussJordan.aspx
*January 29, 2016*

**Math**

y = 4 - x x^2 + (16 - 8 x + x^2) = 16 2 x^2 - 8 x = 0 x( 2x-8 ) = 0 x = 0 or x = 4 y = 0 or y = 4 of course, symmetry :) (0,4) or (4,0)
*January 29, 2016*

**Math**

You are welcome.
*January 29, 2016*

**Math**

y = a x^2 + b x + c 12 = a (1) + b(-1) + c 5 = a(0) + b(0) + c so c = 5 15 = a(4) + b(2) + 5 7 = a - b so a = b + 7 10 = 4 a + 2 b 10 = 4(b+7) + 2 b 10 = 4 b + 28 + 2 b 6 b = -18 b = -3 then a = b+7 = +4 so y = 4 x^2 - 3 x + 5
*January 29, 2016*

**mistake in division**

assuming the first 5 x = 3 x + 6 2 x = 6 x = 3
*January 29, 2016*

**Geometry**

Do you mean: x/3 = (x+2)/5 or x/3 = x + 2/5 ? assuming the first 5 x = 3 x + 6 2 x = 6 x = 2 assuming the second (which you wrote) x/3 = 3x/3 + 2/5 5 x = 15 x + 6 -10 x = 6 x = -3/5
*January 29, 2016*

**math**

You have to give us some dimension, like how far away
*January 29, 2016*

**Physics**

G M1 M2 / 19^2 6.67 * 10^-11 (1.45*10^4)(6.4*10^3) / 361
*January 29, 2016*

**mathematics**

I am not telling. Look at: http://www.mathsisfun.com/associative-commutative-distributive.html Hint - it starts with A
*January 29, 2016*

**Quick calc question**

calc question? LOL s(4) = 4*16 + 4 = 68 miles s(1) = 5 miles distance traveled = 63 miles time = 4 - 1 = 3 hours av speed = 63/3 = 21 miles/hour
*January 29, 2016*

**Quick calc question**

dy/dx = 2 + 4 cos 4 x so cos 4x = -1/2 4x = 180 - 60 degrees = 120 degrees = (2/3) pi so x = pi/6 or 4x = 180+60 or 4 pi/3 so x = pi/3 4 x = 360+180 - 60 = 480 =8 pi/3 so x = 2 pi/3 4 x = 360+180 + 60 = 600 = 10 pi/3 so x = 5 pi/6 too big so pi/6 , pi/3 , 2 pi/3
*January 29, 2016*

**Physics**

(1/2) a t^2
*January 29, 2016*

**No idea**

What ? what is the function ? Use parentheses if needed.
*January 29, 2016*

**Math**

15/2 is 7.5
*January 29, 2016*

**Science**

Yes, that is the only chemical reaction on your list.
*January 29, 2016*

**PHYSICS**

There is a direct answer? Please post it if you find it.
*January 29, 2016*

**Physics help**

http://www.jiskha.com/display.cgi?id=1454030373
*January 28, 2016*

**Physics help**

I have done #4 several times
*January 28, 2016*

**Physics help**

V2n = 1.20 V2e = -.00155 v = sqrt (1.2^2 + .00155^2) or about 1.2 and about North Yes, we agre Hey I am not going to do all these. You have the idea
*January 28, 2016*

**Physics help**

call m = 1 since they are the same Initial momentum N = V2n + 0 Initial momentum E = V2e + 0 final momentum N = 1.25cos44 + .92 cos 71 final momentum E =1.25sin44 -.92sin71 so V2n = 1.25cos44 + .92 cos 71 V2e = 1.25sin44 -.92sin71
*January 28, 2016*

**please use same name**

http://www.jiskha.com/display.cgi?id=1454030373
*January 28, 2016*

**oh my**

4. initial momentum N = 1800 Hey, I just did this
*January 28, 2016*

**Algebra 1**

1. geometric series a r^(n-1) a = .5, r = -2 .5 *(-2)^(n-1) 2. same deal 5 *(-1/3)^n-1 and on and on .....
*January 28, 2016*

**college**

I suspect that the proposed developer EMPLOYS only .....
*January 28, 2016*

**Physics help**

north momentum before = 1800*22 east momentum before = 3200*14 north momentum after = 5000 Vn east momentum after = 5000 Ve so Vn = 1800*22/5000 Ve = 3200*14/5000 v = sqrt (Vn^2 + Ve^2) tan angle east of north (compass heading) = Ve/Vn
*January 28, 2016*

**before you type any more,**

Go back and understand the ones Bob and I have done.
*January 28, 2016*

**maths/physics**

F = G M1 M2/r^2 dF/dr = G M1 M2 [ -2 r /r^4 } = - G M1 M2 (2/r^3)
*January 28, 2016*

**maths/physics**

V = (4/3) pi r^3 dV/dr = (4/3) 3 pi r^2 dV/dr = 4 pi r^2 OF COURSE this is the surface area of the sphere, see why?
*January 28, 2016*

**Physics (**

m = mass = rho * (4/3) pi r^3 A =cross section area = pi r^2 m/A = rho * (4/3) r d/dr (m/A) = (4/3) rho NOTE DISAGREE I guess the density of your sphere is one? Vt is when m g = C * p (1/2)Vt^2 A Vt^2 = 2 m g /(pCA) Vt = [2 m g /(pCA)]^.5 let MA = m/A then Vt = [2 g/pC]^.5 [ m...
*January 28, 2016*

**Physics (**

LOL - she sure has tough ones. It took me a while to figure out the landing on an optimal radius plant one.
*January 28, 2016*

**Well, you asked for it :)**

CHECK THAT ARITHMETIC ! I think you can get the picture from what I did but I did it fast.
*January 28, 2016*

**Physics (Gravitation)**

v = sqrt [ 2 G M/r ] v = [ 13.6 *10^-11 (10^22+r^4)/r]^.5 form is v = [ k (a+r^4)/r ]^.5 we want where dv/dr = 0 0 =dv/dr = .5 k^.5[ (a+r^4)/r ]^-.5 * [r (3 r^3)- (a+r^4)] /r^2 luckily that is zero when [r (3 r^3)- (a+r^4)] = 0 3 r^4 - r^4 = a 2 r^4 = a r^4 = a/2 but a = 10^22...
*January 28, 2016*

**Pre-calc**

Boat A east: x = 13 t Boat B north y = 20 (t-1) d = sqrt (x^2+y^2) d = sqrt [169 t^2 + 400 (t^2-2 t +1) ] d = (569 t^2 -800 t + 400 )^(1/2
*January 28, 2016*

**World History**

How much do we count slaves when figuring how many representatives a state gets in congress these day? When was it legal to drink alcohol? When was it not? What about the entire Bill of Rights, the first ten Amendments to the constitution? Have we always had an income tax? How...
*January 28, 2016*

**Math**

ds/dt = 14 t if t = 7 14 * 7 = 98
*January 28, 2016*

**Math**

58/62 = x/100 x = 93.54 % which rounds to 93.5 %
*January 28, 2016*

**algebra**

I do not understand the problem. If the bridge is 20 feet across the cut, it will stick up 20 feet when you raise it 90 degrees.
*January 28, 2016*

**Math**

The real question is: 33/88 = x/100
*January 28, 2016*

**Math**

33*100/88 = 37.5 % You did it right but to get percent from fraction multiply by 100 and your arithmetic is wrong. 33/88 = .375
*January 28, 2016*

**Ihave about ten times no C in NaCl**

Na = sodium Cl = chlorine no C, carbon
*January 28, 2016*

**Science**

I suspect that you could separate these by distillation
*January 28, 2016*

**Math**

coin 1 **h t coin 2 h 6 4 coin 2 t 4 0 p(6 points) = 1/4 p(4 points) = 1/2 p(0 points) = 1/4 (1/4)6 + (1/2)4 = 2 + 1.5 = 3.5 so I agree with you
*January 28, 2016*

**Physics**

weight = 2 * 10^3 * 9.81 = 19.62*10^3 N mechanical advantage = .75/.005 = 150 (19.62/150)* 10^3 = 130.8 N
*January 28, 2016*

**Science**

salt only has sodium (Na) and Chlorine (Cl) They are however both compounds which are held together by chemical bonds.
*January 28, 2016*

**physics**

10 protons * 1.6*10^-19 C per proton = 16*10^-19 C per atom 16*10^-19 C/atom * 6*10^23 atoms/mol = 96*10^4 C/mol 96*10^4 C/mol * 1 mol/20.2 g = 4.75*10^4 C/gram 4.75*10^4 C/gram * 800 grams = 3801*10^4 = 3.8 *10^7 C Luckily the neutral atoms have an equal number of electrons ...
*January 28, 2016*

**physics**

Oh k is about 9*10^9
*January 28, 2016*

**physics**

F = m a = k Q1 Q2/d^2 so a = F/m m = 27 g = .027 kg Q1 = 32*10^-6 Q2 = -22*10^-6 so F is attractive between them F=(1/.027)k (32)(22)(10^-12)/.79^2
*January 28, 2016*

**physics**

F = k Q1 Q2 / d^2 = 9*10^9 (46)(46)/(36*10^6)
*January 28, 2016*

**Science**

Na = sodium Cl = chlorine no C in there
*January 28, 2016*

**physics**

T = 20.6/4 = 5.15 seconds period between crests wave goes 2.97 m in 5.15 seconds speed of crest = 2.97/5.15 m/s frequency = 1/T since you did not include a question, I am guessing that is what you want
*January 28, 2016*