Wednesday

January 18, 2017
Total # Posts: 28,793

**Science**

potential energy at top = kinetic energy at bottom m g h = (1/2) m v^2 h = v^2/(2g)

*September 5, 2016*

**Probability**

p = 3/13 1-p = 10/13 binomial P(1 in 6)=C(6,1)(3/13)^1 *(10/13)^5 = 6 (3/13)(6.54*10^-4) = 9.06 * 10^-4

*September 5, 2016*

**Physics**

E = ke = (1/2) m v^2 that goes into the brake pads and into the water heating both up to T (1/2)1500 (400) = 4200*8.5 (T-20)+ 890*4(T-25)

*September 5, 2016*

**physics**

20 = 17.7t -(1/2)(2.5)t^2 1.25 t^2 - 17.7 t + 20 = 0 solve quadratic for t t = 1.24 or t = 12.9 well, of course it will get there in 1.24 seconds then, while we are looking the other way, it keeps deaccelerating until it stops, then comes screaming back at the guy taking ...

*September 5, 2016*

**math**

I did one, now you try.

*September 5, 2016*

**math**

g/2 on each bus b-17 on ac bus, 17 boys on hot bus g + b = 73 so b = 73-g on ac bus: 3/5[ g/2 + (b-17)] = g/2 6 [g/2 + (56-g)] = 5g 3 g - 6 g + 336 = 5 g 8 g = 336 g = 42 girls total b = 73 - g = 31 boys total so on ac bus g/2 = 21 b-17 = 14 35 total on ac bus

*September 5, 2016*

**Maths**

Did you try to do it? What did you get?

*September 5, 2016*

**falcon**

http://davidmlane.com/hyperstat/z_table.html

*September 5, 2016*

**physics**

x component = 2 cos 40 + 4 cos 127 y component = 2 sin 40 + 4 sin 127 magnitude = sqrt(x^2+y^) tan^-1 A = y/x where A = angle from x axis

*September 5, 2016*

**Science**

500 (100-T) = 300 (T-20) does not matter what the stuff is as long as it does not change phase (it was not steam at 100).

*September 5, 2016*

**Math**

1/5 = x/25 x = 5

*September 5, 2016*

**chemistry**

I suspect so; both are Ionic compounds but you need a chemist not a physicist.

*September 5, 2016*

**Math**

x - x/5 = 160 4 x /5 = 160 x = 5 * 40 = 200 x/5 = 40

*September 5, 2016*

**value**

.7 pi = c if you mean speed at the rim then v = 25 c/10 meters/second

*September 5, 2016*

**Math**

17, 1 and 2 13, 2 and 5 11, 2 and 7 are there others ?

*September 5, 2016*

**Math**

5 x - 14 + 28 x = ?

*September 5, 2016*

**Differential Calculus**

dV/dt = surface area of water * dh/dt

*September 5, 2016*

**Math**

IF it were three n-1 + n + n+1 = 645 3 n = 645 n = 2 1 5 Now you do it for 5

*September 5, 2016*

**Math**

14*10 - 10*6

*September 5, 2016*

**Statistics**

12 * 5 * 16 * 3

*September 5, 2016*

**College Algebra**

domain in years 0</= x </= 4 range in dollars 0 </= y </= 1000

*September 5, 2016*

**Math**

humm 3^(x-2) = 18 ? = 2 * 9 3^(x-2) = 2 * 3^2 2 = 3^(x-4) log 2 = (x-4) log 3 ================ e^(3x+1) = 10 ? 3x + 1 = ln 10 3x = ln 10 - 1 x = (1/3)ln 10 - 1/3 ====================== xlog 8 = x log 2^3 = 3 x log 2 3 x log 2 = 2 x log 5 - log 5 log 5 = x (2 log 5 -3 log 2) x...

*September 5, 2016*

**Algebra**

sin^2 x = sin x * sin x square root (sin^2 x) = sin x sometimes, can also be -sin x

*September 4, 2016*

**physics**

huh? if it is balanced then zero.

*September 4, 2016*

**Math**

but zero?

*September 4, 2016*

**Math**

say the number is +2 -2 + |2| = 0 which is not 2 say the number is -2 +2 +|-2| = 4 which is not true say the number is +zero -zero + |zero| = zero so sometimes (if zero :)

*September 4, 2016*

**math**

1 car would need 16 days so a car removes 1/16 pile/carday 1/16 pile /carday * 4 days *2 cars = 1/2 pile in 4 days so we need 1/16 pile/carday * n days * 3 cars = 1/2 pile n = 1/2 * 16/3 = 8/3 more days = 2 2/3 more so 4 + 2 2/3 = 6 2/3

*September 4, 2016*

**math**

Hey, I did one. Now you try.

*September 4, 2016*

**math**

13/13 x - 7/13 x = 6/13 x 2/3 * 6/13 x---> brother two 1/3 * 6/13 x --->brother 3 = 6 so 2/13 x = 6 x = 3*13 = 39

*September 4, 2016*

**Chemistry**

They both sink because they both have density greater than water (about 1 g/cm^3) Therefore the one with the greater volume will displace a greater volume of water. If they have the same mass, the one with more volume will be the diamond, because it has lower density.

*September 4, 2016*

**physics**

How could I do this without knowing the force required? Work done = energy in = force in direction of motion * .04 meters

*September 4, 2016*

**Calculus**

maybe take ln of top and bottom (1+2 lnx) --------- 2 lnx 1 + 1/(2 lnx) 1 + 1/lnx^2

*September 3, 2016*

**physics (Simple harmonic motion)**

A sin = .054 A cos = .132 sin/cos = tan(.2+P) = .054/.132 inverse tan for .2+P in radians

*September 3, 2016*

**physics (Simple harmonic motion)**

x= A sin (wt+P v = Aw cos (wt+P) a = -Aw^2 sin (wt+P) = -w^2 x f = m a -kx = -m w^2 x so as you probably know w^2 = k/m here w^2 = 2/.5 = 4 so w = 2 now at t = .1 .263 = A(2)cos(.2+P) -.216 = -A (4)sin (.2+P)

*September 3, 2016*

**Physics**

You had it right. If the tow line does not stretch, they accelerate together. Add masses

*September 3, 2016*

**Physics**

You are welcome :)

*September 3, 2016*

**Physics**

first 8 seconds: v = 0 + 3 *8 = 24 m/s at t = 8m/s x = 0 + 0 t + (1/2)(3)(64) = 96m the brakes for four seconds Vi = 24 a = -5 Xi = 96 t = 4 x = 96 + 24(4) - (1/2)(5)(16) x = 96 + 96 - 40 x = 152

*September 3, 2016*

**Physics**

In your car you measure speed with your speedometer, no negative about it. Tho get velocity you need both speedometer and compass, speed which is absolute value and also direction. If east is positive, west is negative.

*September 3, 2016*

**Physics now the rest**

t = .9 seconds up and .9 seconds down now it is just like the other problem 0 = Vi - 9.81 t 0 = Vi - 9.81(.9) Vi = 9.81*.9 which is about 9 m/s up LOL, final speed down is the same as initial speed up also Vi Note it asks for speed, not velocity, no plus and minus, just speed ...

*September 3, 2016*

**Physics**

The net displacement was ZERO That is a trick question It ended up exactly where it started. It moved a distance, but did NOT displace.

*September 3, 2016*

**Physics**

well, it pauses for in ten zillionth of a second. In other words the velocity goes from upward to downward so it goes through zero :)

*September 3, 2016*

**Physics**

go ahead and post them separately above.

*September 3, 2016*

**Physics**

No, 0 at max height. It stops at the top, then falls

*September 3, 2016*

**Physics**

v = Vi - g t 0 = 24 - 9.81 t t = 24/9.81 h = 24 t -4.9 t^2

*September 3, 2016*

**Algebra**

I bet you mean 4√(490k^2 ) which is 4k √(490) which is 4k √(7*7*10) which is 28 k √10

*September 3, 2016*

**Calculus**

x = 2+ln(y-5) x-2 = ln(y-5) e^(x-2) = y-5 y = e^(x-2) + 5

*September 3, 2016*

**Calculus**

e^0 = 1 2x = 7 x = 3.5

*September 3, 2016*

**math/Calculus**

x = csc y = 1/sin y sin y = 1/x y = sin^-1(1/x)

*September 3, 2016*

**Calculus**

if g' is-1 which is as negative as it could be then g will be +1 at x=1 which is as low as it could be anywhere in the interval. Meanwhile f' could be+1 which would also make f = +1 at x = 1 which is a big as it could be. therefore f is always less than 1 and g always ...

*September 3, 2016*

**algebra**

after a year x = x + .03x = 1.03 x every year multiply by 1.03 2000 (1.03)^6

*September 3, 2016*

**Algebra**

You are welcome and I am from a fishing town north of Boston where we rise early.

*September 3, 2016*

**Algebra**

and in the second one a sign error (x-4y+5)(x-4y-5)

*September 3, 2016*

**Algebra**

Yes, you are right

*September 3, 2016*

**Algebra**

maybe complete the square? (x^2-8xy+16y^2) -16y^2 +16y^2-25 (x-4y)^2 - 5^2 (a-b)^2 = (a+b)(a-b) (x-4y+5)(x-4y+5)

*September 3, 2016*

**Algebra**

I am not sure what you want but 8 = 2^3 125 = 5^3 64 = 2^6 = 4^3 (2x/5)^3 + (4/y)^3 but a^3 + b^3 = (a+b)(a^2-ab+b^2) (2x/5+4/y)(4x^2/25-8x/y+16/y^2)

*September 3, 2016*

**Algrebra**

first line 5 y = 3 x - 9 slope = -3/5 second line assume you mean 2x+ky=11 k y = -2 x + 11 slope = -2/k now for parallel, same slope -3/5 = -2/k k = 10/3 for perpendicular new slope = -1/oldslope 5/3 = -2/k k = -6/5

*September 3, 2016*

**Math**

S + (70+S) + (70 + S + 50) = 730 3 S + 190 = 730 3 S = 540 S = 180 (70 + S + 50) = 120+180 = 300

*September 2, 2016*

**math typo**

1st case (x+1)/(y+1)= 3/4 2nd case. (x-3)/(y-3)= 1/2 not y-4

*September 2, 2016*

**Physics**

755/18 I have a sneaking suspicion that there is more to this question. Surely they then ask for the average velocity for the entire round trip which is zero because you return to the same spot and the total displacement is zero.

*September 2, 2016*

**Physics**

v = g t = 9.8 * 3.5 = 34.3 m/s I agree with you.

*September 2, 2016*

**Physics**

Vi = 3 0 = 9.5 + 3 t - 4.9 t^2 solve for t

*September 2, 2016*

**Algebra 1**

33 - g = 2 g - 9 42 = 3 g g = 14 m = 33-g = 19

*September 2, 2016*

**MISSION**

(pi d^2/4)h = V h = 4 V/(pi d^2)

*September 2, 2016*

**Math concepts**

in the ones place two. 3, 5 note: --- in higher places can be zero, like 010 = 10 so 10 of them in the tens place ten so 20 to date in the hundreds place ten so 200 in the thousands place ten so 2000 10003 is too big so none allowed in ten thousands place so I get 2000

*September 2, 2016*

**Algebra**

maybe you mean h(n) = -3 • 4^(2n+1) ????? h(2n) = -3 * 4 ^(2{2n] +1) = -3 * 4^(4n+1)

*September 2, 2016*

**geometry**

SR = TQ midpoints of equal lengths < SRQ = < TQR base angles of isoceles triangle RQ = QR same line segment so side, angle, side

*September 2, 2016*

**geometry**

ADB is congruent to ADC --- side, side, side the end really

*September 2, 2016*

**S.S**

I guess so, but living in a fishing town I do not call salt marshes an "obstacle".

*September 2, 2016*

**Science**

initial x momentum = .3*5 initial y momentum = 0 final x momentum = .3 Ux + .4(2)cosA final y momentum = .3 Vx + .4(2)sinA tanA = Vx/Ux = sin A / cos A

*September 2, 2016*

**Math**

I do not see your geometry arrangement. However in general change in volume = surface area of liquid * change in surface height dV = Area * dh dV = pi r^2 dh so dV/dt = pi r^2 dh/dt (1/4) = pi r^2 dh/dt so dh/dt= 1/( 4 pi r^2) You will have to find r from your geometry at ...

*September 2, 2016*

**physics**

I guess it goes (you do not tell me) spring x = 0, S down Pivot at x = 0.30, P up Board wt of 30*10 = 300 N at x = 1 down Diver wt of 60*10 = 600 N at x = 2 down P = S + 900 moments about x = 0 .3 P = 300*1 + 600*2 .3 P = 1500 P = 15000/3 = 5,000 N S = P - 900 = 600 N

*September 2, 2016*

**someone please help!! i need to finish this!!**

Too many, ask specific question if stuck. eg cross out first row and column | -2 +6 | | +3 -6 | = 12 - 18 = -6

*September 2, 2016*

**Science help immediately**

Yes, feedback

*September 2, 2016*

**College Physics**

so how many Joules do you need? potential energy = m g h = 3 *10^-3 *9.81* 10^-2 = .5*9*10^-6 V^2 30*9.81 = .5*9 V^2

*September 1, 2016*

**Physics**

the acceleration is about 9.81 m/s^2 down the entire trip velocity is zero at the top. It stops then falls. it went up for 1.9/2 = 0.45 s v = Vi - g t at top v = 0 0 = Vi - 9.81 (.45) so Vi = 9.81*.45 h = Vi (.45) - 4.9 (.45)^2 h is height above your hand

*September 1, 2016*

**Singapore way ? someone expert?**

I suspected from the phrasing of the question that the student is taking a subject based on the Singapore approach. My underlines (like _ ) are intended to be boxes. Did I do this right? I know 18 is right, but the explanation is new for me.

*September 1, 2016*

**Math**

lion _ monkeys _ _ _ total _ _ _ _ what times 4 = 24 6 so Lion 6 monkeys 6 6 6 or 6*3 = 18 (I am trying to learn Singapore math :)

*September 1, 2016*

**Math**

18 4/6 - 17 5/6 17 10/6 - 17 5/6 5/6

*September 1, 2016*

**History! Help!**

When that wild Mongol Tamerlane destroyed the irrigation systems in Mesopotamia (Iraq now) in around 1400 AD it was several thousand years old so surely a few thousand BC

*September 1, 2016*

**math**

By the way there are multiple answers to these for example sin 50 = sin 130 = cos 40 = -cos130

*September 1, 2016*

**math**

Hint: Draw the four Quadrants on a graph Draw line length 1 at 50 degrees up from the x axis Draw line length 1 at 50 degrees up from the -x axis sadme sine for 50 degrees and 180 - 50 degrees so sin 50 = sin 130

*September 1, 2016*

**Social Studies**

I wonder which side of the Interexcolony War Ethan Allen and the Green Mountain Boys took.

*September 1, 2016*

**You decide**

I am simply not going to just give you the answer. What do you think? Meanwhile I will contemplate the state militias at war.

*September 1, 2016*

**English Check**

Whew, that is settled.

*September 1, 2016*

**English Check**

The advice was meant for YOU. ok The advice was meant for ME. ok so which do you think ? Would you really say: "The advice was meant for I" ? They are objects

*September 1, 2016*

**Social studies**

I think the last one, religion.

*September 1, 2016*

**Social studies**

Protestants versus Catholics

*September 1, 2016*

**Social studies**

yes no - property owners. Originally you had to be a Puritan.

*September 1, 2016*

**Social studies**

In North America it was the imported diseases from Europe that wiped out the natives. I suspect the same happened to the south.

*September 1, 2016*

**Social studies**

We are pretty proud of our public school history around here.

*September 1, 2016*

**History**

By the way, during most of WW2, I never really understood that the Japanese were enemy. I thought it was just Germans because I did not know any Germans. Japanese people were friends and neighbors in my life. It was impossible that they were bad guys.

*September 1, 2016*

**History**

They assumed that since they were Japanese in ancestry they might help the enemy Japan. It turned out to be nonsense. { My story: I was in Kindergarten in Honolulu when the Japanese bombed us. Many of my school mates and friends were Japanese Americans. In fact I think the ...

*September 1, 2016*

**History**

I bet you mean "code talkers". That usually refers to Navajo Indians who served the US Army in WW2 as communicators. Foreigners might be able to break most codes but had trouble with Navajo. See for example: http://en.wikipedia.org/wiki/Code_talker

*September 1, 2016*

**Statistics**

http://davidmlane.com/hyperstat/z_table.html

*September 1, 2016*

**chemistry**

Well, I suppose mass was conserved 10.2 + 66.9 = 77.1 ------------------------ You can stop there. ------------------------ Now let's check if they are in the right ratio 2 H2O ---> 2 H2 + O2 2 mols of H2 for every mol of O2 mol of H2 has mass 2 g mol O2 has mass 32 g ...

*September 1, 2016*

**science**

always multiply b something that is the same top and bottom except for the name of the unit for example 100 cm / 1 m is the same top and bottom so is 1 m/ 100 cm so if I have 105 m and I want cm I do 105 m (100 cm/m) = 10500 cm or 2000 mL (1 L / 1000 mL) = 2 L or 3400 g (1 kg/...

*September 1, 2016*

**Math**

slope = m = 4 y = 4 x + b -1 = 4(-5) + b b = 19 y = 4 x + 19

*September 1, 2016*

**Mathematics**

60 * 1/4 = 60/4 = 15 km 36 t = 15 t = 15/36 hour 15/36 * 60 = 25 minutes

*September 1, 2016*