Friday

September 30, 2016
Total # Posts: 27,231

**physics 1**

unless it is a self propelled ball the acceleration is 1 g down, about 9.81 m/s^2

*August 3, 2016*

**algebra**

2/5 * 5/8 = 1/4

*August 3, 2016*

**Calculus1**

no in quadrant one you get a positive result in quadrant two you get a positive result in quadrant three the result is negative, change it to + so 1+1+ |-1| = 3

*August 3, 2016*

**pre cal Huh????**

Trig identity: sin(u+v)= sin u cos v + cos u sin v

*August 3, 2016*

**biomechanics**

power * time = work so if time the same, look at difference in work done which is change in potential energy m g h 60 g .6 = 36 g Joules 90 g .45 = 40.5 g Joules

*August 3, 2016*

**biomechanics**

ke = (1/2) m v^2 pe = m g h where h is height above one meter (1/2) m v^2 = m (9.8) h v^2 = 2 (9.8) h h = 64/19.6 total height = 64/19.6 + 1

*August 3, 2016*

**Biomechanics**

(1/2) m v^2 = m g h v^2 = 2 g h

*August 3, 2016*

**biomechanics**

to convert km/hr to m/s either use Google or head. for example 7 km/hr(1 hr/3600 seconds)(1000 m/km) = 7 /3.6

*August 2, 2016*

**math**

there are 12 + 5 + 3 = 20 marbles in the bag. We do an experiment to find out how many are blue call the probability of a blue one x She picks blue 4 out of twenty times, which is 20/100 = 0.20 Her fingers must reject blue because one would expect 12/20 = 0.60

*August 2, 2016*

**physics**

average force = change of momentum/time = 3 * 25 / .1 Newtons

*August 2, 2016*

**Chemistry**

sample of silver metal is suspected to be contaminated with zinc. A 0.2365 g portion of this metal is dissolved in nitric acid and the silver ions precipitated with excess aqueous NaCl. After filtering and drying, the mass of the precipitate is found to be 0.2865 g. What was ...

*August 2, 2016*

**Math**

A = (1/2) b h h = b - 2 so 60 = (1/2) b(b-2) 120 = b^2 - 2 b b^2 - 2 b - 120 = 0 (b-12)(b+10) = 0 b = 12 h = 10

*August 2, 2016*

**math again ?**

10, been there, done that

*August 2, 2016*

**math**

Yes, that is the desired answer. However it is not really nearly that easy. Assume you have 3438 in your back pocket. If you take that loan you will pay a total of 3960 so the easy answer is you save 522 ======================= Now the hard part. that is 261 per year interest ...

*August 2, 2016*

**science**

.5 mol in 1/5 of a liter is 2.5 mol in a liter ======================= 1 mol / 1 liter 10 mol in 10 liters

*August 2, 2016*

**maths**

b = 4 g + 3 That is all I can say without the other half of the problem.

*August 2, 2016*

**Chemistry**

for Kelvin add 273 for F F = (212-32)C/100 + 32 = (9/5)C + 32

*August 2, 2016*

**Physics**

If your textbook gave you a problem written that sloppily, best find another book.

*August 2, 2016*

**Physics**

Work is force times the distance moved in the direction of the force. 35 * 42 Joules Is the work done by that force. You do not say if there are also other forces like gravity for example or if the force is in the direction of motion here.

*August 2, 2016*

**Physics**

I assume 100 meters is the height of the hill, not the distance down the slope. loss of potential energy = 80 * 9.81 * 100 normal force on slope = 80 * 9.81 *cos 70 friction force = 0.110 * normal force = 0.110 * 80 * 9,81 * cos 70 distance moved down slope = 100 /sin 70 so ...

*August 2, 2016*

**Physics**

F = k x 54 = k * 0.20 k = 54 * 5

*August 2, 2016*

**Algebra 2**

My answer: The area of the circle enclosed by x^2 + y^2 = 100 is the times larger than the area of the circle enclosed by x^2 + y^2 = 25.

*August 1, 2016*

**Algebra 2**

How much larger is the area of the circle enclosed by x^2 + y^2 = 100 than the area of the circle enclosed by x^2 + y^2 = 25?

*August 1, 2016*

**Physics**

stored potential energy = (1/2)k x^2 = (1/2)(400)(.04)^2

*August 1, 2016*

**pre cal**

hypotenuse = sqrt (3+9)= sqrt 12 = 2 sqrt 3 sin = sqrt 3 / hypotenuse cos = 3/hypotenuse etc

*August 1, 2016*

**physics**

h = Vi t - 4.9 t^2 so 42 = 2 Vi -4.9*4 solve for Vi then when is h = 0 again? 0 = Vi t - 4.9 t^2 0 = t (Vi - 4.9 t) t = 0 at start of course then it comes back to ground at t = Vi/4.9

*August 1, 2016*

**Chemistry**

If the pH of a 0.46 M aqueous solution of a weak base is 9.2, estimate the Kb of the base:

*August 1, 2016*

**maths**

p = r - 15 p+5 = (1/2)(r+5) 2 p +10 = r+5 2 p = r - 5 2 p = 2 r - 30 ----------------- 0 = -r +25 r = 25

*August 1, 2016*

**Calculus**

let y = x+3 then dy =dx (y-3) ln y dy = y ln y dy - 3 ln y dy = y ln y dy - 3/y let u = ln y then dv = y dy so v = (1/2)y^2 and du = dy/y so (1/2)y^2 ln y -(1/2)ydy -3/y (1/2)y^2 ln y - (1/4)y^2 - 3/y but remember y = x + 3 :)

*July 31, 2016*

**Typos**

P(A or B) = P(A) + P(B) - P(both A and B) P(A or B) = P(A U B) P intersection which is both at once and your upside down U is P(A)P(B) = .5*.3 = .15 so P(A U B) = .5 + .3 - .15 = .65

*July 31, 2016*

**Math**

P(A or B) but not both = P(A) + P(B) - P(both A and B) P(A or B) = P(A U B) P intersection which is both at once and your upside down U is P(A)P(B) = .5*.3 = .15 so P(A U B) = .5 + .3 - .5 = .65

*July 31, 2016*

**mathfinish your question please**

sum of what equal to what?

*July 31, 2016*

**math**

How bad could it get? 1+2+3+4 = 10 so at least five slips to be sure to get a sum greater than ten.

*July 31, 2016*

**Math**

one way 2 + 1 + 2 + 1 - 4 = 2

*July 31, 2016*

**Math**

http://www.bankrate.com/partners/sem/mortgage-calculator-rates.aspx?s_kwcid=AL!1325!3!114614083448!e!!g!!mortgage+calculator+with+taxes&ef_id=V54ISwAAAH4QPBQk%3a20160731141643%3as

*July 31, 2016*

**English**

You are correct. Chang is not change.

*July 30, 2016*

**math**

Hard to say from your description. But if something came down from height h and had no loss of energy due to friction or whatever then the kinetic energy is equal to the potential energy at the start (1/2) m v^2 = m g h or v = sqrt (2 g h) = sqrt ( 64 h) in the ancient foot ...

*July 30, 2016*

**Calculus AB**

....but the last one I did was fun :)

*July 30, 2016*

**Calculus AB**

a better be 0 if it is the same for + and - x c better be 4 if 2^2 - c = 0 and (-2)^2 - c = 0 so far y = b/(x^2-4) if x = -1 y = b/-3 = 3 so I guesss b = -9

*July 30, 2016*

**Calculus AB**

tan slope angle 1 = m1 tan slope angle 2 = m2 so angle 1 = tan^-1 m1 angle 2 = tan^-1 m2 so theta = angle 2 - angle 1 = tan^-1 m2 - tan^-1 m1 tan theta = tan (a - b) where a =tan^-1 m2 and b =tan^-1 m1 so tan theta = (tan a-tan b)/(1+tan a tan b) [trig identity] = (m2 -m1)/(1...

*July 30, 2016*

**Calculus AB**

(x-r)(x-s) = x^2 + b x + c x^2 - rx - sx + rs = x^2 + b x + c

*July 30, 2016*

**Maths**

1/3 = 2/6 1/2 = 3/6 so 1/6 on wafers so 2/3/1

*July 30, 2016*

**please use one name**

ah come on

*July 30, 2016*

**Calculus AB**

5, 12, 13 right triangle here so sec = 1/cos = 13/5 then 3, 4 , 5 tan = 1/cot = 4/3 so sin = 4/5 so 13/5 - 4/5 = 9/5

*July 30, 2016*

**Calculus AB**

h = ln (sin x) look at this at x = 0, x = pi/2, x = pi/4, x = 3 pi/4 , x = pi , note sin x must be >0 so only quadrants 1 and 2 ln sin 0 undefined ! ln sin pi/4 = -.346 ln sin pi/2 = 0 ln sin 3 pi/4 = -.346 etc :)

*July 30, 2016*

**Calculus AB**

y = a cos (k x - b) + c a and c are easy because c is average of 8 and -2 or 3 and a is thus 5 y = 5 cos (k x - b) + 3 cos is max of 1 at k x - b = 0 k*3-b = 0 so b = 3 k so y = 5 cos (k x - 3 k) + 3 cos is min of -1 at k x - b = pi kx - 3k = pi but x = 7 here so 7 k - 3 k = ...

*July 30, 2016*

**English**

a piece of ONE banana well, again ONE banana or just the singular type of fruit again not two apples but two pieces of apple

*July 30, 2016*

**Math**

if 4 t = 2 pi t = pi/2 if 6 t = 2 pi t = pi/3 so we need at least t = 0 to t = pi/2 or any other interval of length pi/2

*July 30, 2016*

**Math typo**

t = -1 + 5 t ? I doubt it then 1 = 4 t and t = 1/4 x = 2 - 3 (1/4) period

*July 30, 2016*

**Physics**

average force = change of momentum/time

*July 30, 2016*

**Physics**

NEWTON'S FIRST LAW !!!! 75 * 5 = (75+40) * v

*July 30, 2016*

**Physics**

mu static = friction force/normal force = 300/400 similarly mu dynamic = 200/400 Why are you asking questions that I am sure are covered in your text?

*July 30, 2016*

**maths**

ten sides? going around the outside we have to turn right ten times that means each time we turn right 36 degrees which is 360/10 that means the interior angle= 180 - 36 = 144 degrees in radians this is pi - 2pi/10 = 5 pi/5 - pi/5 = 4 pi/5

*July 30, 2016*

**statistics**

We need the sum of probabilities of 6, 7 and 8 This is much more advanced than your previous questions and requires use of the binomial distribution rules. P(x=k) = C(n,k) p^k p^(n-k) where C(n,k)=n!/[k!(n-k)!] so for example the P(x=6) is P(x=6)= C(8,6) .33^6 * .67^2 where C(...

*July 30, 2016*

**math**

b is bigger than a and smaller than c

*July 29, 2016*

**statics is not statistics**

....and statistics is not statics * | 1 2 3 4 5 6 _______________ 1 | 2 3 4 5 2 | 3 4 5 3 | 4 5 4 | 5 5 | 6 | so 10/36

*July 29, 2016*

**statics**

.....and you mean statistics :)

*July 29, 2016*

**statics**

I did NOT say 28 I said 28 divided by the sum

*July 29, 2016*

**statics**

You mean statistics by the way. I replied because I do statics and dynamics. It is just luck I knew the probability question answer.

*July 29, 2016*

**statics**

sum = 33 + 34 + 30 + 28 answer = 28 / sum

*July 29, 2016*

**statistic**

recipe is here: http://davidmlane.com/hyperstat/z_table.html

*July 29, 2016*

**physics**

d = .05 meter Fx = k [Q^2/.05^2]cos 30 from each Fy cancels so it is just 2Fx (repels of course because same sign)

*July 29, 2016*

**general solution**

Call the time, which I think is a typo, T distance is d t1 = time out t2 = time back t1 + t2 = T t1 = d/55 t2 = d/330 so d/55 + d/330 = T d = T /(1/55 + 1/330)

*July 29, 2016*

**too long a time**

7 seconds?

*July 29, 2016*

**math**

Trick question (1/cos A)(cos A) = 1 unless cos A = 0 but what is cos 90 ? If A = 90. in fact the secant is just plain not defined. http://socratic.org/questions/what-is-the-exact-value-of-sec-90

*July 29, 2016*

**probability**

Consider these events independent because there are a lot more than 4 children in Ghana. Use binomial distribution. C(4,4)(.65)^4 (.35)^0 1 * .65^4 * 1 .65^4 note C(n,k) = n!/[k!(n-k)!] defined as 1 for k = 0 see http://www.mathsisfun.com/data/binomial-distribution.html

*July 29, 2016*

**Stats**

http://www.google.com/search?q=david+m+lane+normal+curve&ie=utf-8&oe=utf-8

*July 29, 2016*

**Chemistry**

C2D3 has a solubility product constant of 9.14×10−9. What is the molar solubility of C2D3? Express your answer with the appropriate units.

*July 28, 2016*

**Math**

92 + 64 - (73+89) - (66-49) etc down to -42-(-81)-(-73)=? = -42 + 81 + 73

*July 28, 2016*

**makes no sense**

how much time? how many km, whatever?

*July 28, 2016*

**math**

One faucet fills 100 gal in 18 min so a faucet does (50/9) gal/min 6 *(50/9) t = 25 6*(2/9)t = 1 t = 9/12 = 3/4 minute

*July 28, 2016*

**math**

2016 - 2000 = 16 16 * 7 = 112 224 - 112 = 112 half the original

*July 28, 2016*

**mathematics**

x(g+b) have not finished .65 g have not finished .55 b have not finished .65 g + .55 b = x(g+b) but g = 3 b so .65(3 b)+.55 b = x ( 4 b ) (1.95+.55)b = 4 x b x = 2.5/4 = .625 so 62.5 %

*July 28, 2016*

**world history**

First of all, who says? Although the habit is to treat Chinese dynasties as succeeding, there is no reason they should not have overlapped. That said, they had, as the Chinese always had, nomadic tribes to the north and west and the bleak ocean to the east. Mostly mountains ...

*July 27, 2016*

**science(physics)**

momentum = 0.100 * 20 = 2 kg m/s distance into plank = .020 meter average speed in plank = 20/2 = 10 m/s time in plank = .020/10 = .002 s average force = change in momentum/time = 2/.002 = 1000 Newtons

*July 27, 2016*

**math**

(9/36)*900 = 900/4 = 225

*July 26, 2016*

**Math**

This is not a submarine but a research submersible. Submarines do not go much deeper than a couple of boat lengths. 8 * 60 + 37 = 517 seconds 517 seconds * 25 ft/s = 12,925 feet Although that is far deeper than a submarine dives, it is less than half as deep as the Mariana ...

*July 26, 2016*

**Chemistry**

How much H3PO4 is needed to neutralize 1 liter of a 0.75M solution of NaOH? (in moles)

*July 26, 2016*

**Math**

8 sin 30 + 8 sin 120 8 (1/2) + 8 (1/2) sqrt 3

*July 26, 2016*

**math**

must be combined age? p = 2 j p-17 + j-17 = 33 p + j = 67 2 j + j = 67 3 j = 67 j = 67/3 = 22 1/3 so p = 134/3 = 44 2/3

*July 26, 2016*

**physics**

h = Hi + Vi t - 4.9 t^2 v = Vi - 9.81 t when is v = 0 ? (the top) t = 30/9.81 = 3.06 seconds coasting up to a stop so h = 50 + 30 (3.06) - 4.9 (3.06)^2

*July 26, 2016*

**Physics**

You kidding? 200 - 3(45)

*July 26, 2016*

**physics**

v = Vi - 9.81 t h = Hi + Vi t - 4.9 t^2 42 = 0 + Vi(2) - 4.9(4) Vi = 30.8 meters/ second when it hits ground, v = -30.8 m/s v = Vi - 9.81 t -30.8 = 30.8 - 9.81 t t = 6.28 seconds

*July 25, 2016*

**Chemistry**

Thank you so much!

*July 25, 2016*

**Chemistry**

What volume of nitrogen dioxide (in L) is produced from the complete reaction of 16.87 of lead (ii) nitrate at STP

*July 25, 2016*

**college physics**

time for one wave = period = 1/f = 10/30 so f = 3 Hz

*July 25, 2016*

**physics**

u = 10 m/s forever v = -gt = -9.81 (3) = - 29.4 m/s check if it hit the ground d = (1/2) g t^2 = 4.9 * 9 = 44.1 so still in the air speed = sqrt (10^2 + 29.4^2)

*July 25, 2016*

**Maths**

a + 20 = 3 (180-a) a + 20 = 540 - 3 a 4 a = 520 a = 130 180-a = 50

*July 25, 2016*

**Maths**

(n + m)/2 = 15 so n + m = 30 m = (30-n) (n m )^.5= 9 n m = 81 n(30-n) = 81 -n^2 + 30 n = 81 n^2 -30 + 81 = 0 (n-3)(n-27) = 0 3 and 27

*July 25, 2016*

**General Mathematics**

http://www.jiskha.com/display.cgi?id=1469428320

*July 25, 2016*

**Maths**

7 +8 +3 = 18 so 2 are white 2/20 = 0.1

*July 25, 2016*

**huh? typos?**

maybe 2 meters deep and find volume not height? if so v = w L d = 20 *100 *2 = 4,000 m^3

*July 25, 2016*

**Math (Rational Inequality)**

x^2 h = 8 x = sqrt(8/h) if h = x x = h = 2 if x > h, not allowed if x < h then h > 2 so x < 2

*July 25, 2016*

**algebra**

Well, you know 48 = 16*3 You know that 3/3 = 1 so multiply 3/16 by 3/3 and get 9/48

*July 25, 2016*

**ststistics**

binomial distribution p = .24 1-p = .76 n = 10 P(2) = C(10,2).24^2 (.76^8) but C(10,2) = 45 so 45 * .0576 * .111 = .288 P(1) = 10 * .24 * .76^9 = .203 so answer to b is 1 - .288 - .203 c is same way but boring. you do it

*July 25, 2016*

**Hey wait a minute**

This is very, very similar to one I already helped you with. Please try them yourself. It does not do you any good to have us do all the problems for you. The idea is that we can help, but not do virtually the same problem over and over for you. http://www.jiskha.com/display....

*July 24, 2016*

**MATH**

let x = tan t then dx = sec^2 t dt sec^2 t dt/[ tan t (1+tan^2 t) ] NOTE: 1+tan^2 t = sec^2 t !!! wow that helps :) so we have dt/tan t = ctn t dt = ln (sin u)

*July 24, 2016*

**Math**

u = 1 - y^2 du = -2 y dy or dy = du/-2y ((y^3)/(u^2))[du/-2y] (-1/2)y^2 du/u^2 but y^2 = 1-u so -(1/2)(1-u) du/u^2 = (u/2)du/u^2 - (1/2)du/u^2 = (1/2) du/u - .5 u^-2 du finish and check my arithmetic :)

*July 24, 2016*

**Someone Please Help me- PreCalc**

x^2 + y^2 = 1 16/49 + y^2 = 49/49 y^2 = 33/49 y = +/- sqrt (33) /7 so since in Q IV where y is negative (4/7, -sqrt(33)/7 )

*July 24, 2016*

**physics**

10 * 100

*July 24, 2016*