Tuesday

July 7, 2015

July 7, 2015

Total # Posts: 21,431

**Social Studies**

China is over 90% Han. As for the rest, think !
*November 24, 2014*

**Algebra Huh ?**

Please check for typos. If you have a line y = m x + b then the line perpendicular to that will have slope = -1/m so y = -(1/m) x + c and they cross at right angles
*November 24, 2014*

**physics**

I do not know what this means. Nothing is ever perfect, but after rounding off experimental results such as 1.51 and 1.52 to two significant figures they are both 1.5 so the difference would be zero (0.0) although it is not zero in real life.
*November 24, 2014*

**Physics**

Well, you need to ignore friction. If so then: Initial velocity up = Vi v at top = 0 so 0 = Vi - 9.8 t where t it time at top so t at top = Vi/9.8 so Vi = 9.8 t total time in air = 2 t = Vi/4.9 You measured 2 t evidently so divide your total time by 2 to get rise time t height...
*November 24, 2014*

**physics**

180 km/hr = (180/3.6) m/s so to run 1000 meters takes 1000 (3.6/180) = 20 seconds energy used = 560,000 Joules/s * 20 sec = 11,200,000 Joules 165 km/hr = (165/3.6) m/s 1000 (3.6/165) = 21.8 seconds energy used = (783) *21.8 = 17,083 Joules so 11,200,000 - 17,083 I do not ...
*November 24, 2014*

**math**

q = 2 d .25 q + .10 d = 3.6 .25(2 d) + .1 d = 3.6 .6 d = 3.6 6 d = 36 d = 6 so q = 12
*November 24, 2014*

**physics**

work = force * distance in direction of force so power = work/time = force * speed in direction of force 2.5 * 10^7 Watts This ignores and interaction between the flow around the plane in free stream and the propulsion system.
*November 24, 2014*

**Physics**

u = 40 forever so x = 40 t Vi = 0 v down = 0 + 9.8 t = 9.8 t z = height at top - 4.9 t^2
*November 24, 2014*

**science**

Vi = v sin 27.7 0 = Vi - 9.8 t t = v sin 27.7 /9.8 that is time to the top total time in air = 2 t = 2 v sin 27.7/9.8 u = v cos 27.7 d = (v cos 27.7)(2 v sin 27.7 /9.8) d = (2 v^2/9.8) cos 27.7 sin 27.7 but 2 cosA sinA = sin 2A d = (v^2/9.8) sin (55.4) either do d for v = 7.6 ...
*November 23, 2014*

**add error**

24 c = 360 c = 15 t = 20
*November 23, 2014*

**algebra**

t = c + 5 8 t + 16 c = 400 ================= 8 t - 8 c = 40 8 t + 16c = 400 ----------------- subtract -8 c = -360 c = 45 etc
*November 23, 2014*

**physics**

nope the frequency does not change. The speed of the wave changes so the length changes. There is no place to store leftover crests and troughs if you try to get five out one end per second while putting four in the other end
*November 23, 2014*

**physics**

Pe1 = 1.5 * g * h Pe2 = 4.5 * g * h so Pe2 = (4.5/1.5) (7)
*November 23, 2014*

**PLEASE HELP PHYSICS**

I think 1 is true. I can change the frequency of the sound waves from my lips by changing the frequency I generate them at. In fact the wave frequency is the generator frequency.
*November 23, 2014*

**PLEASE HELP PHYSICS**

1. sure, whistle different notes. 2. I agree false. 3. I agree true.
*November 23, 2014*

**Physics**

The paper runs out when the child has run 40 meters. The rest is irrelevant. 40 = (1/2) at^2 80 = .35 t^2 t = sqrt (80/.35)
*November 23, 2014*

**Trig- math**

You are welcome.
*November 23, 2014*

**Trig- math**

http://www.mathopenref.com/heronsformula.html
*November 23, 2014*

**physics**

work in = drag force * length of ramp (in other words the work done by the person dragging) gain in PE = m g h = 65 * 9.8 * 2 efficiency = 100(gain in PE/work in)
*November 23, 2014*

**trig**

need to know mu, friction coef if there is no friction, let mu = 0 F - mu (70) cos A = (70) sin A if mu is zero then F = 90 sin A so sin A = 36/90
*November 23, 2014*

**Statistics**

http://davidmlane.com/hyperstat/z_table.html
*November 23, 2014*

**Physics**

so what is the question?
*November 23, 2014*

**science**

well, baking soda and vinegar make models go fast. Vinegar is acid, baking soda is what you want. Lye soap is pretty caustic. Bleach maybe Borax. Mostly stuff you use for cleaning.
*November 23, 2014*

**Math**

60 - (-29) = 60 + 29 = 89
*November 23, 2014*

**Physics**

well, not quite the last part after you find t, the time, is d = (1/2) a t^2
*November 23, 2014*

**Physics**

Now that is quite enough. You are asking really the same question over and over again.
*November 23, 2014*

**Physics**

same as your last question 0 = 215/3.6 + a (2.7) a will be negative because braking
*November 23, 2014*

**Physics**

90 km/hr = (90*1000/3,600) m/s v = 0 + a t 90/3.6 = a (10) a = 9/3.6 m/s^2
*November 23, 2014*

**math**

9 + (9+.5 b) + b but b = (9 + 9 + .5 b = 18+.5 b .5 b = 18 b = 36 so 18 + 18 + 36 so answer: 72 or six feet check head = 9 body = 36 tail = 36-9 = 27 9 + 36 + 27 = 72 sure enough
*November 23, 2014*

**physics**

normal force = 400 g cos 35 friction force up slope = .6 (400 g) cos 35 weight component down slope = 400 g sin 35 400 a = 400 g sin 35 - .6 (400 g cos 35) a = g (sin 35 - .6 cos 35) = .082 g
*November 23, 2014*

**Algebra**

first 10,000 for 3 years 10,000 (1.10)^3 then second year deposit 10,000 (1.10)^2 then 10,000 (1.10) or 10,000 (1.1^3 + 1.1^2 + 1.1)
*November 21, 2014*

**Physics**

You are welcome.
*November 21, 2014*

**Physics**

I w before = I w after by conservation of angular momentum 3.1 * 8 - 10.2 * I = -2.6 (3.1+I)
*November 21, 2014*

**ET1210- Dc/Ac Circuits**

p = V i but i = V/r so p = V^2/R and thus R = V^2/p
*November 21, 2014*

**ET1210-Dc/Ac Circuits**

the voltage drops equally through each resistor if in series (same current through each and V=iR) so V/number
*November 21, 2014*

**Math**

I do not know. Make sure you have no typos. I think it was meant to be easier.
*November 21, 2014*

**Math**

81 = 3^4 so 3^4x = 64 27 = 3^3 so we want 3^(3x+3) 3^4x = 2^6 4x log 3 = 6 log 2 x = 6 log2 /4 log 3 = 1.5 log2/log3 = whatever, calculator so y = 3^(3x+3) log y = (3x+3) log 3 find log y take 10^log y = y
*November 21, 2014*

**Physics**

it has not only (1/2) m v^2 but also (1/2) I w^2 where w = angular velocity if it does not slip then w = v/r I = (2/3) m r^2 for thin spherical shell so ke = (1/2) m v^2 + (1/2) m (2/3) r^2 v^2/r^2 mgh = (1/2) m ( v^2 + 2/3 v^2) h = (1/2g) (5/3) (3.83)^2
*November 21, 2014*

**science**

Density is mass/unit volume Inertia is resistance to change in motion mass is a scalar measure of how many neutrons and protons you have degrees is either a measure of temperature or angle or something you get when you graduate
*November 21, 2014*

**Math**

a (2)^r = 1 so a = 1/2^r a (32)^r = 4 but 32 = 2^5 a (2)^5r = 4 2^5r / 2^r = 4 2^4r = 4 so 4 r = 2 r = 1/2 check a = 1/sqrt 2 a sqrt(32) = sqrt 32/sqrt 2 = 4 sqrt 2/sqrt 2 = 4 sure enough
*November 21, 2014*

**Math - makes no sense**

You either have a typo or your text was written in some other universe. r ? what r? from your first constraint a = 1/4 that does not work for your second constraint
*November 21, 2014*

**Algebra Help please!**

No, do P2 now P2 = 6,000 (1.03)^16 then find P2 -P1
*November 21, 2014*

**s.s**

cold and hungry committed to General Washington and the cause of independence
*November 21, 2014*

**Physics**

20 radians = (1/2)alpha t^2 20 = (a/2) (8.7)^2 a = 40/8.7^2 = .528 v = a t = .528 * 8.7 = 4.60 rad/s yes Ac = v^2/r = omega^2 r = 8.7^2 (.25)
*November 21, 2014*

**algebra 2**

6 x^2 - x - 1 = 0 x = {1 +/- sqrt (1 +24) } /12 (1 +/-5) /12 1/2 or -1/3
*November 21, 2014*

**science**

water is about 1000 kg/m^3 we have 140 m^3 of water so 140,000 kg of water the force of gravity on that is 9.81 * 140,000 = 1,373,400 Newton's third law says the bottom of the pool has to push up with that same force 1,373,400 Newtons pressure = force/area = 1,373,400/(10*...
*November 21, 2014*

**Math**

4/3 = 8/6 7/2 = 21/6
*November 21, 2014*

**Physics**

It goes up, then down for 1.05 s do the vertical problem Hi = 2 final h = 0 h = Hi + Vi t - 4.9 t^2 0 = 2 + 1.05 Vi - 4.9 (1.05)^2 -2 + 5.4 = 1.05 Vi Vi = 3.24 m/s initial speed up Now the horizontal problem max speed * sin 10 = 3.24 so speed = 18.7 m/s so u = 18.7 cos 10 = 18...
*November 21, 2014*

**Math**

interest = 5 * 10,000 * .07 = 3500 interest = 10,000 * 1.06^5 - 10,000 = 3382.26 subtract
*November 21, 2014*

**Physics**

well, then you have your answer F = (1/2) 217 (.625)^2 / .195
*November 21, 2014*

**Physics**

I = (1/2)m r^2 F (.195) = I alpha since you did not say what the angular acceleration alpha is, I can not do anything more for you
*November 21, 2014*

**physics**

impulse = change in momentum = 9*11 + 9*8 kg m/s
*November 21, 2014*

**Chemistry**

H2O = 18 g/mol, 16 of which is O so we have in the water (16/18)(10) = 8.89 kg of O that is 8890 grams or 556 mols of O or 278 mols of O2 in the water how many mols of O2 did we end up with in the air T = 273+25 = 298 do P V = n r T, solve for n or know that 1 mol is 22.4 ...
*November 21, 2014*

**physics**

.001 * .065 Nm
*November 21, 2014*

**mixture problems**

fat = f .45 f + .03 (500) = .05 (500+f) or .40 f = .02(500)
*November 21, 2014*

**Algebra**

25 x = y - 500 so x = (1/25)y - 20 y is already solved for
*November 21, 2014*

**Math Help!!!**

x = xi + delta x -2+1 = -1 y = yi + delta y -5+3 = -2 (-1,-2)
*November 21, 2014*

**Math Help!!!**

5 - no idea 8 - no idea 7 - NO - y is the same, x changes sign so (-8,-10) the first on the list
*November 21, 2014*

**physics**

by conservation of momentum 2.8 * speed of rifle back = .00984*726 solve for speed of rifle back, Vr Ke = (1/2)(2.8)(Vr)^2 + (1/2)(.00984)(726)^2
*November 21, 2014*

**phisics**

vertical problem first Vi = 551 sin 12 v = Vi - 9.8 t v = 0 at top so t = Vi/9.8 at top total time in air = 2 t = Vi/4.9 now horizontal: u = 551 cos 12 distance = u (Vi/4.9)
*November 21, 2014*

**Math**

5 times Greg's age is 55, 5 G = 55 so Gregg's age is 55/5 or G = 55/5 which is 11 11 + 11 + 11 + 11 + 11 = 55
*November 21, 2014*

**math**

do it this way (distributive property of multipication): = -q(q^2-2) + 3(q^2-2) then combine like terms or use FOIL if you happen to know the system. It is really the same thing.
*November 21, 2014*

**math**

-1 (p+5)(p-5) in general a^2-b^2 = (a+b)(a-b) so this is -1(p^2-25) which is 25-p^2 or use distributive property as I did in your other problem
*November 21, 2014*

**Math**

You left t out ! max at 15 min min at 15+14 = 29 so 14 min from sin = +1 to sin = -1 that is half a period so T = 28 min 2pi t/T = 2 pi at t=T we disagree about all this so pi t/14 is 2 pi when t = T = 28 range from max to min = 2 A = 125-99 = 26 so A = 13 (check with you :) ...
*November 21, 2014*

**Physics**

I * omega = the same I gets smaller so omega gets bigger
*November 21, 2014*

**math**

v+c=23 v-c=11 ========add 2 v = 34 v = 17 mph
*November 21, 2014*

**physics**

a = -7 miles/s^2 I assume you mean but your units look screwy. Perhaps you mean -7 miles per hour/second and I will do that alternative at the end but please read what you wrote in the future before posting. Vi = 40/3600 miles/second v = Vi - 7 t 0 = 40/3600 - 7 t t = .0016 ...
*November 20, 2014*

**math 3**

z = (x-mean)/sigma so x = mean + z*sigma 1.25*7 = 8.75 cents 1.25 + .0875 = $1.34
*November 20, 2014*

**algebra**

I need 2 mol of H2SO4 so I need 2/10.01 dm^3 of concentrate = .1998 dm^3 of concentrate
*November 20, 2014*

**physics**

.045 kg / (25 *10^-6 m^3) = 1800 kg/m^3 1.8 times density of water ? Are you sure data is correct? 25 cm^3 of water has mass of 25 grams
*November 20, 2014*

**math**

210 = (h+3) (L +2) = h L + 3 L + 2 h + 6 or h L + 3 L + 2 h = 204 L(h+3) = 204-2h L = (204-2h)/(h+3) A = L h A = h(204-2h)/(h+3) for max dA/dh = 0 = h[(h+3)(-2) -204+2h]/(h+3)^2 +(204-2h)/(h+3) =h[-2h-6-204+2h]/(h+3)^2 +(204-2h)/(h+3) =-210 h/(h+3)^2 + (204-h)(h+3)/(h+3)^2 = ...
*November 20, 2014*

**physics - need radius**

need radius of wire, not just current R = V/i = .0320/1.35 = .0237 Ohms = resistivity * Length/area so resistivity = .0237 * pi r^2 /2.8 table of conductivity and resistivity here http://hyperphysics.phy-astr.gsu.edu/hbase/tables/rstiv.html
*November 20, 2014*

**math**

y = k sqrt x 6 = k (2) k = 3 y = 3 sqt x y = 3 (5) y = 15
*November 20, 2014*

**Math**

17,000 + 3 $/gal * (1/22) gal/mi * Mi = 23,000 + 3 * (1/50) * Mi
*November 20, 2014*

**Algebra2**

log2 [(x+8)/5] = 4 (x+8)/5 = 2^4 = 16 x+8 = 80 x = 72
*November 20, 2014*

**math please help**

no, see my reply below.
*November 20, 2014*

**thermodynamics**

(1/2)m v^2 = 625(1600) Joules divide by 1000 for kJ that is also the work to stop it in kJ
*November 20, 2014*

**math thanks for your help**

3 (-2)^3 +5(-2) - 6 every term is negative for x = -3 so no way
*November 20, 2014*

**science**

P V = n R T same pressure ? V/T = n R/P = consatnt V1/T1 = V2/T2 6/(2T2) = V2/T2 V2 = 3 in^3
*November 18, 2014*

**geometric progression**

a , ar , ar^2 , ar^3 , ar^(n-1) ar^2 = 10 ar^5 = 80 ar^5 / ar^2 = 8 r^3 = 8 r = 2 ====================================== now you do the second one.
*November 18, 2014*

**physics**

d = (1/2)(9.8)t^2 10 = 4.9 t^2 t = 1.43 seconds falling v = a t v = 9.8 (1.43) = 14 m/s , yes right Your way is fine. I just cheated to get it faster.
*November 18, 2014*

**physics**

P = m V m (2) = 100 m = 50 kg
*November 18, 2014*

**Algebra**

power = V i = V( V/R) = V^2/R sure enough to triple the power at the same V, use 1/3 the resistance R This can be done easily and very understandably by running three of the original Rs in parallel, like turning three stove burners on instead of one.
*November 18, 2014*

**Algebra**

Yes, it makes sense, 7 times further is 1/49 th of brightness
*November 18, 2014*

**Algebra**

7*7 = 49 which is about 50
*November 18, 2014*

**Math**

12 - 18 = -6
*November 18, 2014*

**Math**

2 is D.
*November 18, 2014*

**algebra 1**

-64 = -4*-4*-4 = -4^3 (x^8)^1/3 = x^(8/3) (x^5)^(1/3) = x^(5/3 -4 x^(8/3) y^(5/3)
*November 18, 2014*

**Physics**

sin^-1 (1/1.49)
*November 18, 2014*

**Physics**

NET force = 2100 - 1800 !!!!!!!
*November 17, 2014*

**Physics**

1. a = F/m = (2100-1800)/1200 2. d = (1/2) a t^2 = 50 a 3. v = a t = 10 a
*November 17, 2014*

**Algebra - quick question**

if y = a e^kx then dy/dx = = k a e^kx = k y if it is discrete yn+1 = yn + k yn = (1+k) yn hen yn+1 - yn = k yn in other words the change = constant times present value
*November 17, 2014*

**math**

t = FINAL tuna e/(t-15) = 2/3 e/t = 1/3 so finally t = 3 e e/ (3e -15) = 2/3 3 e = 6 e - 30 e = 10 t = 3 t = 30
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

if interest rate is 2% per year compounded yearly then Yn+1 = Yn + .02 Yn = Yn (1.02) and in general Y = Yinitial * (1.02)^n
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

The important thing here is that the rate of change is proportional to your present value, so the change keeps changing. The most common example is compound interest
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

I believe 1 and 6 are the same question asked different ways.
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

Yes, it told you to keep doing it until you get to 11.04, that was after 5 days (I cheated and took the log of both sides so solve directly)
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

10.82 fifth day 10.82*1.02 = 11.04 done
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

I guess I did not explain very well in the first question for example it asks you to plug and chug from 0 to 11.04 I did not bother but first day 10*1.02 = 10.2 second day 10.2 * 1.02 = 10.4 third day 10.4 * 1.02 = 10.61 fourth day 10.61 * 1.02 = etc until you get to 11.04
*November 17, 2014*

**Algebra - Can you PLEASE check - I**

11.04 = 10 (1.02)^n I am not going to try lots of days, boring log 11.04 = log 10 + n log 1.02 4.996 days so five days 2. n>0 and <the life of the plant 3. when n = 0, height = 10 4. the height of the plant when we bought it 5. F(n+1) = F(n) * 1.02 6. calculate F(1) = 10...
*November 17, 2014*