Tuesday

February 21, 2017
Total # Posts: 29,375

**maths/science**

just like the other one v = - g t -63.7 = -9.81 t

*September 28, 2016*

**maths**

let g = 9.81 m/s^2 then v = -gt = -9.81*7 m/s or if using clunky units g = 32 ft/s^2 v = -32*7 ft/s

*September 28, 2016*

**Math**

I do not know what "break apart" means. But if I did not already know the answer I would think 54 = 60 - 6 = 10*6 - 1*6 = (10-1)6 distributive property = 9 * 6 so 9

*September 28, 2016*

**Math**

-1 +6 -1 +6 -1 +6 so 20-1 = 19 19+6 = 25 25-1 = 24 24+6 = 30 etc

*September 28, 2016*

**Math**

(1/4)(2/3) = 2/12 = 1/6

*September 28, 2016*

**Physics**

(a) w = normal force on floor = (9.81+2.70)8.06 (b) w = (9.81-2.70)8.06 friction force = .402 w in each case

*September 28, 2016*

**Science**

I have a sneaking suspicion that you are correct :)

*September 28, 2016*

**AP Calculus**

when slope is +, velocity is to right when slope is -, velocity is to left when curvature is + acceleration is + (holds water) when curvature is -, acceleration is - (sheds water)

*September 28, 2016*

**copy and paste does not work here**

I do not see your choices.

*September 28, 2016*

**Math**

draw it but 15 play all three 20 play b ball and hockey of which 15 are in all three so 5 play only b ball and hockey

*September 28, 2016*

**Math**

y = k x 6 = k (-2) k = -3 15 = -3 x x = -15/3 x = -5

*September 28, 2016*

**Math Help!!!**

3 1/2 → 1 1/4 no 7/2*1/2 = 7/4 = 1 3/4 5 3/4 → 2 1/8 no 23/4 * 1/2 = 23/8 = 2 7/8 3 1/6 → 1 7/12 yes 19/6 *1/2 = 19/12 = 1 7/12 4 1/2 → 2 1/4 yes 9/2*1/2 = 9/4 = 2 1/4

*September 28, 2016*

**algebra 2**

I can not see your choices but x^2 is always </=0 so y>/= 7

*September 28, 2016*

**Physics**

at h/4 total mechanical energy = m g(h/4)+(1/2)m (18)^2 at h total mechanical energy = m g h + 0 so gh = gh/4 + 9*18 for part b (1/2)m v^2 = m g h

*September 28, 2016*

**Physics**

north 7 and east 5 hypotenuse sqrt(49+25)

*September 27, 2016*

**Mechanics**

sin 30 =Fy/50 cos 30 = Fx/50

*September 27, 2016*

**English**

2. Choose the meaning of the bold word. Failing that, I could have SURREPTITIOUSLY dumped the whole outfit overboard, written off the forty or so dollars as love’s tribute. (“The Bass, the River, and Sheila Mant") happily*** slyly ##################### ...

*September 27, 2016*

**math**

first person does 1/60 job/min second does 1/90 job/min together they do 1/60 + 1/90 = 3/180 + 2/180 = 5/180 job/min so (5/180)t = 1 job t = 180/5 = 36 minutes

*September 27, 2016*

**Physics**

ride speed = 20 m/50 s = .4 m/s total speed = .4 + .5 = .9 t = d/speed = 20/.9 = 200/9 = 22.2 seconds part b speed = .5 - .4 = .1 20/.1 = 200 seconds

*September 27, 2016*

**Physics**

u = 50 cos A Vi = 50 sin A 240 = u t = 50 t cos A so t, time in air, = 24/(5cosA) time rising = t/2 = 12/(5 cos A) v = Vi - g t rising 0 = 50 sin A - 9.81(12)/(5 cos A) 250 sin A cos A = 9.81(12) now use trig to get angle A for second part you have two values of Vi = 50 sin T ...

*September 27, 2016*

**Math**

weeks = days/7

*September 26, 2016*

**Math**

5*15 does not work either :)

*September 26, 2016*

**Math**

32-17 = 15 w = 17*5 + 15*6 by the way I bet they mean centimeters not millimeters.

*September 26, 2016*

**physics**

46 N

*September 25, 2016*

**maths**

5(x+iy)(x-iy)+3(x+iy -x +iy) =42-15i 5x^2+5y^2 + 6iy = 42-15i 5 x^2 + 5 y^2 = 42 6 i y = -15i y = -15/6 5 x^2 + 5 (225/36) = 42

*September 25, 2016*

**Physics**

kinetic energy at planet surface = potential energy at max height (1/2) m v^2 = m g h h = v^2/2g so if g is g earth/6 then the height is h earth * 6

*September 24, 2016*

**Science**

http://www.jiskha.com/display.cgi?id=1474739216

*September 24, 2016*

**Math**

combinations of 9 taken 3 at a time = 9!/[ (9-3)!(3!)] = 9*8*7/(3*2) = 3*4*7 = 12*7 = 84

*September 23, 2016*

**Physics**

g force down slope = mg sin phi friction force up slope = mu mg cos phi a = F/m = g sin phi - mu g cos phi = g (sin phi - mu cos phi)

*September 23, 2016*

**Physics**

To raise something to a power please use ^ symbol To divide please use / symbol work done = kinetic energy gained = (1/2)mv^2 power = work done/time = (1/2) m v^2 t = m v^2 /(2t)

*September 23, 2016*

**Physics**

average speed = .568/2 = .284 m/s time = t = .389/.284 = 1.37 seconds a = change in speed / change in time = .568/1.37 = .415 m/s^2 F = m a = 79.5*.415 = 33 Newtons

*September 23, 2016*

**Physics**

Well, yes but it was the change in POTENTIAL energy m g h. The velocity is assumed negligible.

*September 23, 2016*

**Physics**

400*9.81 = 3924 Newton weight I guess the mechanic is also on the ground?mechanical advantage needed = 3924/250 = 15.7 since pulleys do not come in fractions we will need 16 times 16*3 = 48 meters

*September 23, 2016*

**Physics**

+i +j +k -5 -3 -4 +0 +1 +0 = 5 k + 4 i or 4i +0j +5k (note obviously perpendicular to j so no j component)

*September 23, 2016*

**Social studies**

I would claim horses. Try: http://latinamericanhistory.about.com/od/theconquest/a/09armsconquest.htm

*September 23, 2016*

**Social Studies**

no, please read what I said.

*September 23, 2016*

**Social Studies**

Native to Brazil. Portuguese brought it to West Africa.

*September 23, 2016*

**Engineering Math**

x = Xi e^-kt .41 = e^-120k ln.41 = -120 k k = .00743 .5 = e^-.00743 t ln.5 = -.00743 t t= 93.3 daya so I pretty much agree with you .77 = e^-.00743 t t = 35.2 days

*September 23, 2016*

**Math**

You are welcome.

*September 23, 2016*

**Math**

|-13| = +13 which is not -13

*September 23, 2016*

**Social studies NEED HELP**

What does your book say? Does it discuss the Portuguese going east around Africa to the Indian Ocean and East Indies? Does it mention that other European countries might want to find another way to get there and that Columbus thought he could get to the East Indies by sailing ...

*September 23, 2016*

**algebra**

a + (n-1)d .5 + (n-1).5

*September 23, 2016*

**algebra**

http://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html

*September 23, 2016*

**algebra**

.5 , 1 , 1.5 , 2.0 , 2.5 is .5 , 1.5 3.0 , 5.0, 7.5 on day 5 of course this is an arithmetic sequence with d = .5

*September 23, 2016*

**physics**

assume you mean 10^7 and 10^-16 etc How long to move 35*10^-3 m ? t = 35*10^-3/1.9*10^7 so t = 18.4 * 10^-10 seconds a = F/m = 6*10^-16 / 9.11*10^-31 = .659 * 10^15 m/s^2 d = (1/2) a t^2 = (1/2)(.659*10^15)(339*10^-20) = 112*10^-5 = .00112 meters or 1.12 mm

*September 23, 2016*

**Math**

n-1 , n , n+1 4(n-1)-13 = n+1 4 n - 4 - 13 = n+1 3 n = 18 n = 6 5, 6, 7

*September 23, 2016*

**Social Studys**

How about "no taxation without representation" ?

*September 21, 2016*

**jay**

P/2 = L+w w = P/2 - L

*September 21, 2016*

**jay**

A = h (a+b)/2 2 A/h = a + b a = 2A/h - b

*September 21, 2016*

**equation is wrong !**

h(a+b)/2 not times 2 average base times height, common sense

*September 21, 2016*

**Math**

use 4y-6 for x y = 4 - 3 (4y-6) y = 4 - 12 y + 18 13 y = 22 y = 22/13 x = 4(22/13) - 6 x = 88/13 - 78/13 x = 10/13

*September 21, 2016*

**Math**

I think you mean 12 grams and 40% 12 = .4 x so x = 12/.4

*September 21, 2016*

**Science**

How about mountain ranges for example ?

*September 21, 2016*

**Algebra**

I knew the slope m so I used y = m x + b I put in 2 for x and -3 for y that is the point (2,-3) -3 = (1/3)(2) + b

*September 21, 2016*

**Algebra**

slope = m = (-4+3)/(-1-2) = -1/-3 = 1/3 -3 = (1/3)(2) + b b = -9/3 - 2/3 = -11/3 y = (1/3) x -11/3 3 y = x - 11 x -3 y = 11

*September 21, 2016*

**PHYSICS**

yf = yo + vo t + (1/2) a t^2 yf = 0 yo = unknown vo = 0 (dropped not thrown) vf irrelevant ( = a t) a = -4.9 indeed t = 3.5 so 0 = yo + 0 -4.9 (3.5)^2 or yo = 4.9 (3.5)^2

*September 21, 2016*

**statistics**

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

*September 21, 2016*

**Science**

Huh? v = a t so a = 15/10 = 1.5 m/s^2 not 2.5 m/s^2 Something is wrong with the problem statement.

*September 20, 2016*

**Math**

(4 km/cm)(4 cm) = 16 km

*September 20, 2016*

**science**

water is neutral lime juice and HCl are acidic NaOH is basic

*September 20, 2016*

**Chemistry**

What do you think? Imagine doing this and measuring how much is in the beaker by the lines on the side.

*September 20, 2016*

**physic**

so the increase in speed of the dropped one cancels the slow down of the other and height = initial speed up * time = 20*3 = 60

*September 20, 2016*

**World History**

I would say the competent leadership, perhaps B

*September 19, 2016*

**science**

m g = 200 * 5 Newtons work = PE = m g h = 200 * 5 * 1 Joules work/time=power = 200 * 5 * 1 / 100 Joules/second or Watts

*September 19, 2016*

**Algebra**

well, I think I would multiply the first one by three and the second one by two 15 x + 12 y = -42 6 x + 12 y = 12 ------------------ subtract 9 x = -54 or x = -6 then -18 + 6 y = 6 6 y = 24 y = 4 (-6 , 4 )

*September 19, 2016*

**Influential Ideas and Events Quiz( Check Answers)**

Those were my choices as opposed to your choices. The First Amendment one I feel strongly about though :) The Bill of Rights starts off with freedom of speech, the very first thing.

*September 19, 2016*

**my guesses**

d) people who live together under a sovereign government c) It mediates conflicts and supports international projects b) self-reliance c) The leader of Britain is chosen by the legislature (Parliament) (Prime Minister) First Amendment!!!! Congress will make no law abridging ...

*September 19, 2016*

**math**

4 c + 2 h = 78 c+h = 35 so 2h = 70-2c 4 c + 70 - 2c = 78 2 c = 8 c = 4 35 - 4 = 31 hens

*September 19, 2016*

**Algebra 2**

fifth root of n = n^(1/5)

*September 19, 2016*

**Algebra 2**

x^(3/5) i^2 = -1 i^3 = -i i^4 = 1 i^5 = i i^6 = -1 i^7 = -i i^8 = 1 note pattern i^64 = 1 and i^63 = -i

*September 19, 2016*

**physics**

the center of gravity moves up 1.5 meters m g h = 20 * 9.81 * 1.5

*September 19, 2016*

**maths help me**

energy/second: mgh + (1/2) m v^2 where m = mass/second what is mass/second? m = 1000 kg/m^3 * pi (.05^2)m^2 * 50 m/s

*September 19, 2016*

**physics**

1000 * 9.81 * Vol = 25-15 = 10 N so Vol is about .001 m^3 25/.001 = 25,000 N/m^3 or about 2500 kg/m^3 or about 2.5 times that of water

*September 19, 2016*

**Physics**

h = 20 t - 4.9 t^2 15 = 20 t -4.9 t^2 4.9 t^2 -20 t + 15 = 0 solve quadratic for two values of t little t on the way up big t on the way down

*September 18, 2016*

**Physics**

acceleration F = m A dF/dt = m dA/dt (unless the mass changes:)

*September 18, 2016*

**Maths**

2 km + (3/8)j + (1/2)j = 1 j 2km = (8/8 - 4/8 - 3/8)j 2 km = j/8 j = 16 km total you do the rest now :)

*September 18, 2016*

**Math**

n + n+1 = 2n + 1 2n is even the next one is odd :)

*September 18, 2016*

**Math**

.41 L + .21 (8-L)= 2.08 .41 L + 1.68 - .21 L = 2.08 .20 L = .40 L = 2 p = 8-L = 6

*September 18, 2016*

**Math**

x-4 + x-2 + x + x+2 + x+4 = 50 5 x = 50 x = 10

*September 18, 2016*

**Math**

n-2 + n + n+2 = 3 n which you can divide by 3 :) It does not matter that they are odd

*September 18, 2016*

**Use parentheses**

I do not know what you mean x^3 + 1/(1/x^3) or what you said which is x^3 + 1 + 1/x^3 ???? if the first multiply top and bottom of second term by x^3 x^3 + x^3/1 = 2x^3

*September 18, 2016*

**whoops, go with Reiny**

I missed that this is a binomial distribution problem. The combinations are not equally likely.

*September 18, 2016*

**Math**

easier grid for me h -> 0 1 2 3 4 t -> 4 3 2 1 0 I see five possible outcomes of which 2 work so I get 2/5 HHTT is the same here as TTHH or HTTH

*September 18, 2016*

**Physical Science**

work = force * distance in direction of force 310 = force * 1.5 force = 310 J/1.5 m = 207 Newtons

*September 18, 2016*

**Math**

10 a + 5 s = 1700 so s = 340 - 2 a s+a = 270 340 - 2a + a = 270 a = 340-270 a = 70

*September 18, 2016*

**Physics**

v = a t = 2.46 t x = -10 + (1.23) t^2

*September 18, 2016*

**Math**

15 + .25 t = 20 +.05 t .20 t = 5 t = 25

*September 18, 2016*

**science**

4*12+10 = 58 grams/mol 14.17/58 = .244 mol 2C4H10 + 13 O2 ---> 10H2O + 8 CO2 mols CO2 produced = .244(8/2)=.977 mol 2*12+16 = 40 grams/mol 40 g/mol * .977 mol = 39.1 grams

*September 18, 2016*

**Math**

t = 4 c t+c = 360 5 c= 360 c = 72 t = 288

*September 18, 2016*

**calculus and chemistry**

T = Ts + (To-Ts)e^-(kt) Ts = T surrounding = 10 To = initial T = 160 60 = 10 +(150)e^-(5k) e^-(5k) = .333333 -5k = -1.1 k = .22 so 20 = 10 + 150 e^-.22t e^-.22 t = .0666666 .22t = 2.71 t = 12.3 min 12.3 - 5 = 7.3 min more

*September 18, 2016*

**Maths**

r = triangle leg = 20 so is the base 20 so equilateral so 60/360 = 1/6 of circle (1/6)2 pi r =(1/3)pi 20 = 20.94 cm

*September 18, 2016*

**Physics**

work done = loss of ke = (1/2)m v^2 = 1000*625 Joules power = work/second = 1000 * 625 / 5 Watts

*September 18, 2016*

**Integrated Math**

correct

*September 18, 2016*

**messed up link**

http://en.wikipedia.org/wiki/Galileo%27s_Leaning_Tower_of_Pisa_experiment

*September 18, 2016*

**physics**

The weight does not matter (Google Galileo, http://en.wikipedia.org/wiki/Galileo%27s_Leaning_Tower_of_Pisa_experiment) about 9.81 m/s^2

*September 18, 2016*

**scince**

10 log base ten of power ratio or in this case 10 log 20 about 13 dB If by "intensity" the question means amplitude rather than power then it is 20 log or about 26 dB

*September 18, 2016*

**Physics**

http://www.bbc.com/news/business-27021610

*September 17, 2016*

**Physics**

a = change in velocity/change in time = (-10 - 10)/5 = -20/5 = -4 m/s^2 v = vi + a t at t = 2 v = 10 -4*2 = 2 m/s at t = 3 v = 10 -4*3 = -2 m/s

*September 17, 2016*

**PRE-CAL**

yes, about 55 years 10% doubles in about 7 years :)

*September 17, 2016*

**Physics (Mechanics)**

straight up I guess (1/2) m v^2 = m g h h = 22^2/(2*9.81) total height = .8 + h

*September 17, 2016*