Tuesday

February 21, 2017
Total # Posts: 29,375

**Science**

two problems connected only by falling time vertical problem: Vi = initial y velocity = 0 v = Vi - g t h = Hi + Vi t - .5 g t^2 so at ground 0 = 0.6 + 0 - 4.9 t^2 t^2 = 0.6/4.9 t = 0.35 s to fall v at ground = 9.81* 0.35 horizontal velocity = 2.4 until it hits range = 2.4 * .35

*February 12, 2017*

**Algebra**

3 a + 9 c = 183 6 a + 13 c = 276 multiply first equation by 2 6 a + 18 c = 366 6 a + 13 c = 276 ---------------- subtract 5 c = 90 c = 18 etc

*February 12, 2017*

**Math**

32/8 1*8 = 8 2*8 = 16 3*8 = 24 4*8 = 32 5*8 = 40 6*8 = 48 7*8 = 56 8*8 = 64 9*8 = 72 10*8= 80

*February 12, 2017*

**English**

Is that chair related to you? Or is that the stairs groaning like your baby coyote?

*February 12, 2017*

**Science**

initial T = 0+273 P V= n R T same n and R so 2P * 2V = n R (4T) 4*273 = 1092 K which is 1092-273 = 819 C

*February 12, 2017*

**physics**

in Part A y = Vi t - 4.9 t^2 30 = Vi(2)- 4.9(4) 2 Vi = 49.6 Vi = 24.8 agreed Part B 15 = 24.8 t - 4.9 t^2 4.9 t^2 - 24.8 t + 15 = 0 t = [ 24.8 +/-sqrt(24.8^2-4*4.9*15) ]/9.81 =[24.8+/- 17.9]/9.81 use smaller t for on the way up .702 seconds

*February 11, 2017*

**physics**

I am not going to just do these for you in general magnitude = sqrt (xcomponent^2+ycomponent^2) tan angle from x axis = ycomponent/xcomponent) to do A + B say C = (Ax+Bx)i + (Ay+By)j where i and j are unit vectors in x and y directions

*February 11, 2017*

**Physiscs**

If it passes through the bar along the axis of the bar, the moment of inertia is small because the mass is close to the axis of rotation. Remember that mR^2 stuff. It is not zero though unless the radius of the bar is zero :) It is in fact a slender solid cylinder and its ...

*February 11, 2017*

**Physics**

Trace ray from the top of A and then another from the bottom of A

*February 11, 2017*

**Physics**

identical

*February 11, 2017*

**physics**

reaches top 3.6/2 or 1.8 seconds after launch at top, v = 0 but v = Vi - g t in meters, seconds g = 9.81 m/s^2 so 0 = Vi -9.81 t 0 = Vi -9.81*1.8 Vi = 17.7 meters/second

*February 11, 2017*

**math**

1.02 x = 7150 so x = 7150/1.02

*February 11, 2017*

**maths**

2*20 =

*February 11, 2017*

**pre calc**

top = L^2 bottom = L^2 4 sides = 4*13L total = 2 L^2 + 52 L

*February 10, 2017*

**algebra**

Good ! You are welcome.

*February 10, 2017*

**algebra**

no, look below carefully 3.2*10^2 LY ( 5.88*10^12 mi/LY) = 18.8 * 10^14 mi = 1.88 * 10^15 mi

*February 10, 2017*

**easy algebra question, check answer**

yes 3*10^1 * 3*10^5 = 9*10^6 because x^a * x^b = x^(a+b)

*February 10, 2017*

**can not help**

Since I do not know what it looks like. You can not copy and paste here.

*February 10, 2017*

**Math**

4*10 = 40 10 * 10 = 100 so eleven, but the raft only holds ten :)

*February 10, 2017*

**Social Studies**

You are welcome.

*February 10, 2017*

**Social Studies**

Well, I would have picked A, although I would put it much more strongly. The Soviet Union effectively took absolute control of countries like Poland, Czechoslovakia, Hungary, East Germany ..... Google "Winston Churchill Iron Curtain speech"

*February 10, 2017*

**Ms Sue?**

We are volunteers, for the most part teachers, who are happy to help students, but not to do tests for you. Force = rate of change of momentum = d/dt (m v) if m is constant ( no mass change due to exhaust or fast fuel use or what ever) then: F = m dv/dt F = m a where a is ...

*February 10, 2017*

**Physics**

40*9.81*.4 = work done power = work /second so P = 40 * 9.81 * .4/.5 = 314 Watts if you used 10 m/s^2 for g you would get C

*February 10, 2017*

**Physics**

25 * 200 = v * 900 v = 5.55 so yes, A

*February 10, 2017*

**do not see pictures**

If you tried to post diagrams, that does not work here.

*February 9, 2017*

**Science**

1 = 10 log P/Po where log is base 10 0.1 = log P/Po 10^.1 = P/Po P/Po = 1.259

*February 9, 2017*

**Math**

You are welcome.

*February 9, 2017*

**Math**

steps >/= 10,000 - 5,274

*February 9, 2017*

**Physics 202**

for rock: T = 2 pi sqrt (L/g) T = 2 pi sqrt (.5/g) for ball Tb = 5 T so 5 T = 2 pi sqrt (Lb/g) =================== 10pi sqrt (.5/g) = 2pi sqrt (Lb/g) 5 sqrt (.5) = sqrt(Lb) 25 (.5) = Lb Lb = 12.5

*February 9, 2017*

**Math**

dR/dx = 1500 - 3000*2/(2x+3)^2 if x = 150 dR/dx = 1500 - 6000/303^2 = $1499.93 per unit the point is that you have an initial 1000 setup cost then it is $1500 per unit but that decreases as the number goes up and you train robots

*February 9, 2017*

**maths fractions**

1/4 = 3/12 1/3 = 4/12 x/12 - 3/12 = 4/12 x/12 = 7/12

*February 9, 2017*

**20/15 in lowest terms.Express your answer mixed n**

sorry 1 1/3

*February 9, 2017*

**20/15 in lowest terms.Express your answer mixed n**

divide top and bottom by 5 4/3 = 3/3 + 1/3 = 3+1/3 = 3 1/3

*February 9, 2017*

**Math**

6 out of 20 do not like it. 6/20 = 30/100 or 30%

*February 9, 2017*

**mathematical literacy**

2 of cement 2 of lime 2*5 = 10 of sand 2 of water

*February 9, 2017*

**history please help! Check my answers!**

Flowers are major, and are only in the third choice, so yes, right.

*February 9, 2017*

**math**

ah 40,000 (1.07)^2

*February 9, 2017*

**math**

h = 9 - (x+3)^2 = 9 - x^2 -6 x - 9 = -x^2 - 6x slope = dh/dx = -2x -6 zero when x = -3 curvature = d^2h/dx^2 = -2 so that is a maximum then what is h? -x^2 - 6 x = -x (x+6) when x = -3 3 (3) = 9 which we could have said in the beginning because x^2 is always + so 9-x^2 is ...

*February 9, 2017*

**PHYSICS**

u = 1.12 forever Vi =initial vertical velocity = 0 v = Vi - 9.81 t h = Hi + Vi t - 4.9 t^2 h = 27.8 - 4.9 t^2 0 = 27.8 - 4.9 t^2 so t = sqrt (27.8/4.9) use that t to get horizontal range x = 1.12 t

*February 9, 2017*

**physics**

t cos 52 = (24/2)9.81 = 12*9.81

*February 9, 2017*

**History - please check my answers**

1. I would include the check on gov power 2. The First amendment is about Congress NOT MAKING A LAW ABRIDGING the right of the people peaceably to assemble. I am not aware of anything about public versus private property in the First Amendment, although there is case law on ...

*February 9, 2017*

**calculus**

64 = (4/3)pi R^3 from that find R dV = surface area * dR (easy way :) so dV/dt = 4 pi R^2 dR/dt 20 in^3/min = 4 pi R^2 dR/dt solve for dR/dt

*February 9, 2017*

**Calculus review**

arc tan t where t = x^2 so arc tan x^2 (it is how fast the area is changing at the right side of the area, the high limit of t)

*February 9, 2017*

**Geometry**

Diameter = 4' radius = 2' = 24 inches Area = pi r^2 = 576 pi in^2

*February 9, 2017*

**Math**

r+4 = 2(a+4) or r - 2a = 4 You need to know something more.

*February 9, 2017*

**maths**

(5/8)(152) = 5*19 = 95

*February 9, 2017*

**Physics**

does the water just stop or continue moving with the child? it it continues moving on the child for an instant, you have 90 kg, not 30

*February 9, 2017*

**Math**

Do + Da = 41 Do + 5 = 2(Da+5) 41 - Da + 5 = 2 Da + 10 etc

*February 9, 2017*

**Math**

LOL, subtract 3 from the answers to the question above.

*February 9, 2017*

**physics**

luckily a right triangle with legs of 3 and 4 has a hypotenuse of 5 so there is no need to use c^2 = a^2 + b^2 to get the magnitude. The cosine of the angle south of west is 3/5 so the angle is 53.13 degrees south of west which is 180 + 53.13 degrees counterclockwise from the ...

*February 9, 2017*

**physics**

west = 2.5 km south = 10 km magnitude = sqrt(6.25 +100) tan of angle south of west = 10/2.5 = 4 angle south of west = 76 degrees south of west

*February 9, 2017*

**Math - Derivatives**

dy/dx = x^3 +2x^2 -5x +6 = 12 x^3 + 2 x^2 - 5x -6 = 0 x = -3 , -1 , +2 http://www.wolframalpha.com/widgets/view.jsp?id=b858339e64fa997454dd12f77cb1ece1

*February 9, 2017*

**physics**

32 s more,

*February 8, 2017*

**Math 8th grade**

well six one hours plus 2 half hours = 7 hours

*February 8, 2017*

**Algebra**

.5 D + 1 B </= 6

*February 8, 2017*

**Math**

T = L + 19 T + 4 = 2 (L+4) =================== L+19 + 4 = 2 L + 8 L = 15 T = 34

*February 8, 2017*

**Oh maybe it means**

does not do 40 for the whole 20 sec, but only for 20 - 4 = 16 s so 100 + 40*16 = 640 + 80 = 820 ..... not a choice though.

*February 8, 2017*

**physics**

The trick is to use average speed for a time of constant acceleration v = Vi + a t Vf = final v = Vi + a t Vf -Vi = a t so a = (Vf -Vi)/t d = Vi t + .5 a t^2 d = Vi t + .5 (Vf-Vi)t^2/t d = Vi t -.5 Vi t + .5 Vf t d = .5(Vi+Vf) t BUT .5(Vi+Vf) IS the average speed during ...

*February 8, 2017*

**physics**

average 20 for first 5 so 100 m go 40 for 20 s so 800 more now brake average 20 for 4 = 80 980 so I agree

*February 8, 2017*

**math**

What does full mean? Multiply by 3 every day? That is called geometric sequence http://www.mathsisfun.com/algebra/sequences-sums-geometric.html Say A is amount on day 1 then on day 12 you have A(3)^11 and on day 4 you have A(3)^3 3^11/3^3 = 3^8 = 6561 so you have 6561 times as...

*February 8, 2017*

**World history**

LOL, I guess you would not have a list of answer choices for this. In fact this requires at least a bookcase full of history texts and research papers and I am not sure how to do anything but point you to a few web sites. I guess start with the rivers (Tigris and Euphrates) ...

*February 8, 2017*

**Math**

-3 / (1/2) = -3(2/1) = -6/1 = -6

*February 8, 2017*

**Maths**

common multiple 5 2*2*2 2*2*3 need 5 2 2 2 3 120

*February 8, 2017*

**Math**

lol, square has at least 4 how many does a circle have ? ;)

*February 8, 2017*

**Maths**

alpha^.5 = [b +sqrt(b^2-4c)]/2 beta^.5 = [b -sqrt(b^2-4c)]/2 alpha =(1/4) [ b^2 +2bsqrt(b^2-4c)+b^2-4c] beta =(1/4) [ b^2 -2bsqrt(b^2-4c)+b^2-4c] alpha + beta = (1/4) [4 b^2 -8 c] = b^2 - 2 c etc ....

*February 8, 2017*

**physics**

10^4 km = 10^7 meters !!!! well the force on 1kg is the value of g there :) F = G * 1 * M /R^2 F =6.67*10^-11 * 6 *10^6 /(16*10^14) I think you probably have a typo

*February 8, 2017*

**Math**

-5 = -a+b-c dy/dx = 3 a x^2 + 2 b x + c = 4 at x = -1 so 3a - 2b + c = 4 d^2y/dx^2 = 0 = 6ax +2b = -6a+2b so b = 3 a 3 a -6a + c = 4 -5 = -a +3a -c -3a + c = +4 +2a - c = -5 ------------ 5 a = 9 etc check my arithmetic

*February 8, 2017*

**Math Independent & Dependent.**

the cost depends on how many c = 7 s http://nces.ed.gov/nceskids/help/user_guide/graph/variables.asp

*February 8, 2017*

**Calculus unit review**

draw a graph point A is (1/11) f(5) = f(1) + integral 1 to 5 (f' dx) = 11 + 9 = 20 or just say integral from 1 to 5 of (dy/dx) dx = y(5)-y(1)

*February 8, 2017*

**Math**

before x students 5x/8 boys and 3x/8 girls so later 3x/8 + 6 = 5x/8 3 x + 48 = 5 x 2 x = 48 so x = 24 students before x+6 = 30 after 6 girls arrived

*February 8, 2017*

**how many minutes**

hours = minutes/60 speed = 63 miles/those hours

*February 7, 2017*

**math**

1.20 x

*February 7, 2017*

**Math**

(7/8)(16/1) = 7*16/8 = 7*2 = 14

*February 7, 2017*

**Math**

hat is zero at -3, -3 , 2 ,2 , -5 the double roots mean the curve just touches the axis at: -3 and +2 when x is big positive, it is big positive when x is big negative it is big negative y = 180 when x = 0 so starts at lower left crosses x axis at x=-5 goes up then dips down ...

*February 7, 2017*

**Physics**

total energy is constant until it hits the ground. Potential turns to kinetic. m g h = 8 * 9.81 * 100 Joules

*February 7, 2017*

**History**

I am inclined to agree with you. See: http://en.wikipedia.org/wiki/Freedmen's_Bureau_bills although in practice it turned out more like B and even that was undermined by the KKK etc.

*February 7, 2017*

**Math - limits**

in radians sin t --> t + t^2/2! -t^3/3!..... so in radians sin t/t --->1 as t--->0 however we are doing degrees do t degrees which is (pi t/180) rad so we have sin (pi t/180) /t which becomes (pi t/180 +(pi t/180)^2/2 ... divided by t ----> pi/180 as t--->0...

*February 7, 2017*

**Math**

15/12 = 5/4

*February 7, 2017*

**Math**

agree

*February 7, 2017*

**Math**

1 / 3

*February 7, 2017*

**math**

Smith: 1 teen drinks 2/3 case / 5 weeks so 1 teen drinks 2/15 case / 1 week ===============================Jones 1 teen drinks 5/6 case / 4 weeks so 1 teen drinks 5/24 case / 1 week ======================== smith 2/15 jones 5/24 which is bigger? 15 = 3*5 24 = 3 * 8 3*8*5 = 120...

*February 7, 2017*

**math**

Once again 192 - 150 = 42 NOT 142

*February 7, 2017*

**Social studies**

ok :) Then I agree with you.

*February 7, 2017*

**spelling ?**

mass crowding maybe? If so yes.

*February 7, 2017*

**error**

192=k+54c............................. (1) 150=k+14c. ........................... (2) subtract (1) from (2) 142=40c ============================= whoops 42 not 142

*February 7, 2017*

**physics**

mg + mv^2/r = 1000 Newtons g = 9.81 m/s^2 v = 7.4 m/s r = 11.2 m solve for m

*February 7, 2017*

**statistics**

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

*February 7, 2017*

**Physics**

yes, true power = V i but V = i R so Power = i^2 R = V^2/R Joules per second or "Watts" Energy (or heat) = Power * time so indeed H = i^2 R t = V^2/R Joules Now how much heat do we need? H = mass * specific heat * change in temp H = 0.5 * 4.19*10^3 * 70 Joules so in ...

*February 7, 2017*

**Science**

x = sin (2 pi t/T) 1/2 = sin (2 pi t/24) 2 pi t/24 = pi/6 because pi/3 radians= 30 degrees and sin pi/6 = 1/2 t/12 = 1/6 t = 2

*February 7, 2017*

**Math**

L = 31.5 w = (4/7)31.5 = 18 p = 2 * 31.5 + 2 * 18 A = 31.5 * 18

*February 7, 2017*

**Science**

force = change in momentum/time 10 N = 10 kg *V / 10 s V = 10 m/s ============= or F = m a 10 = 10 a a = 1 m/s^2 v = a t v = 1*10 = 10 m/s

*February 7, 2017*

**physics**

v = a t 100 m/s = a ( 5 s) s = 20 m/s^2

*February 7, 2017*

**Physics**

By the way, GOOGLE Archimedes

*February 6, 2017*

**Physics**

weight in water = WW Newtons weight in air = WA Newtons mass = WA/9.81 kilograms (if your scale reads in kilograms, multiply by 9.81 m/s^2 on earth to get Newtons) difference = WA-WW = buoyant force = volume*density of water * 9.81 density of water = 1,000 kg/m^3 so difference...

*February 6, 2017*

**algebra**

typo maybe?

*February 6, 2017*

**algebra**

you have 0k so you can not solve for k

*February 6, 2017*

**physics**

a = dv/dt = 6.24 so v = constant + 6.24 t at t = 0, v = Vi so v = Vi + 6.24 t 9.36 = Vi + 6.24 * .44

*February 6, 2017*

**Math**

think ! 1. It starts in 1990 at 1,000,000 2. it DECREASES and you meant to the POWER t, not times t a k^t not a k t to check at 2010, t = 20 years y = 1,000,000* .98^20 ?

*February 6, 2017*

**order does matter, typo by me**

Write the number of permutations in factorial form, then simplify. How many differnet ways can you and four of your friends sit in the backseat of a limousine? A. 4!;24 b.4!120 C.5! 120 D. 5! 720 There are 5 of you. Order does matter so permutations of 5 taken 5 at a time 5! =...

*February 6, 2017*

**PLLZ!PLLZ help with math quick!!!!!**

Ariel wants to choose 5 players for her basketball team. There are 7 players to choose from.How many different teams can Ariel make? A. 21 B.32 c.42 D.56 =============================== combinations in grade seven? C(n,r) = n!/[r!(n-r)!] = 7!/[5!(2!)] = 7*6/2 =21...

*February 6, 2017*