Monday

August 31, 2015
Total # Posts: 21,819

**physics**

a. h = (1/2) g t^2 so 4.9 t^2 = 15 find t b. v = gt c. u is constant. There is no vertical force u = 4/t
*June 25, 2015*

**Physics**

work = change in Ke = (1/2)(2)(1^2-4^2) = -15 J negative because energy taken out not put in work = force * distance in direction of force -15 = F (10) F = -1.5 N impulse = change in momentum I = 2 ( 1 - 4) = -6 kg m/s
*June 24, 2015*

**whoops**

or one fourth of the way from S along the altitude from S to the line connecting O and O SHOULD BE a distance A/4 along the altitude from S to the line connecting O and O
*June 24, 2015*

**physics**

Well, I do not see your diagram. However the angle from O to S to O is usually considered to be 120 degrees so if the distance from S to O is A and the mass of an O is m then CG is along the line joining S to the midpoint of O - O How far from S ? Well we have 2 m on the left ...
*June 24, 2015*

**algebra**

Yes although 7 + 1 x is the same as 7 + x because one times anything is that same old anything.
*June 24, 2015*

**algebra**

I answered one like this a few minutes ago. You should be able to use that to figure it out.
*June 24, 2015*

**world history**

......but when I Google Neanderthal brain size I find they have bigger brains than we. What makes you think they are our ancestors? Humans and Neanderthals lived in Europe at the same time for a while. Perhaps they interbred, but I am not sure they count as our ancestors. http...
*June 24, 2015*

**world history**

picture framing? Perhaps farming? If farming, then: herding is most often practiced by nomadic tribes who do not farm (cowboys?) nomads do not usually farm farmers may hunt, but only on vacation during deer season. I suspect that to really develop the use of metals you need to...
*June 24, 2015*

**world historia**

Yes, the main thing I remember is that they were forgotten for a long time :)
*June 24, 2015*

**algebra**

5 - 3 x
*June 24, 2015*

**world history**

As far as I know both used brick walls. Also there is some evidence that Harappan script resembled Sumerian cuneiform but I am not sure it is considered cuneiform. I guess I might pick B
*June 24, 2015*

**Physics**

at one meter from the hinge at the wall you have 491 N down at 1.5 meters from the wall you have T sin 30 up moments about hinge at wall yield: (T sin 30) * 1.5 = 491 * 1 T (1/2)(3/2) = 491 T = 491 * 4/3
*June 24, 2015*

**science**

16 = .380 * Normal force
*June 24, 2015*

**Physics**

check the replies listed below your question. The numbers are different but the method should be clear. eg http://www.jiskha.com/display.cgi?id=1426366344
*June 24, 2015*

**Physics**

during free fall for 3.5 s: v = g t = 9.8*3.5 = 34.3 m/s when we pt on the brakes h = (1/2) g t^2 = 4.9 (3.5)^2 = 60 meters so far, now we stop we are going at 34.3 m/s and slow down at 2 g 0 = Vi - 2 g t so t = 34.3 /19.6 = 1.75 seconds braking h = Vi t - (1/2)(2*9.8) t^2 = ...
*June 24, 2015*

**maths**

x y = 25/42 x (-20/7) = 25/42 x = (25/42)(-7/20) x = (5/4)(-7/42) x = (5/4)(-1/6) x = -5/24
*June 24, 2015*

**Algebra**

Hey, I just did one like this for you.
*June 24, 2015*

**Algebra**

x = length y = width x + 2 y = 9000 or x = 9000 - 2 y A = x y so A = (9000-2y)y 2 y^2 - 9000 y = - A y^2 - 4500 y = -A/2 y^2 - 4500 y +(4500/2)^2 = -A/2 + 5,062,500 (y-2250)^2 = -(1/2)(A-10,125,000) so width = 2250 length = 4500 area = 10,125,000 m^2
*June 24, 2015*

**Math**

7 * pi *r^2 = 137.375 so r = sqrt (137.375/[7 pi]) then C = 2 pi r
*June 24, 2015*

**pragati s.s.h.s.s**

For example Joules is Force*distance = mass * acceleration * distance kg m/s^2 * m = kg m^2/s^2
*June 23, 2015*

**physcial science**

Well, speed of sound in air is around 343 m/s depending on pressure, humidity etc the lightning light travels so fast we will assume we see it when it happens. so d = 7.9 s * 343 m/s = 2710 m or 2.7 km away t = 2.7 km /20 km/h = .135485 hours * 60 min/hr = 8.1 minutes
*June 23, 2015*

**Algebra**

No way. I just did one like this for you.
*June 23, 2015*

**Algebra**

do you know about completing the square? (3x + y)(3x+y)= 9 x^2 + 6xy + y^2 6 y = 16 y = 8/3 y^2 = 64/9 so 9 x^2 + 16 x + 64/9
*June 23, 2015*

**Algebra**

(z-2+3i)(z-2-3i) = 0 now multiply
*June 23, 2015*

**Algebra**

when b^2 - 4 a c is negative a^2 - 400 <0 -20 < a < +20
*June 23, 2015*

**Science**

radius = 5 meters .18 m/s^2 is probably the centripetal acceleration. I can not imagine why it is called "rate". acceleration = v^2/R v^2 = .18 * 5 = .9 v = .95 m/s
*June 23, 2015*

**ICP**

By the way I have no idea what ICP is and I just happened to stumble on your question. Identify your subject next time please.
*June 22, 2015*

**ICP**

10 * 30 cos 25 Work is component of force in direction of motion times distance moved.
*June 22, 2015*

**history**

Assume you mean France. Other countries (eg: USA) managed to install something like democracy without anything like happened in France, but you better read up on the subject and say a lot more than I just did. In particular read previous responses to this question below.
*June 22, 2015*

**Algebra**

22.5 x + 35 (1250 -x) = 27.5 (1250)
*June 22, 2015*

**typo**

You gave grades for 4 tests not five. I will assume total of 5 (70 + 80 + 79 + 69 + x)/5 = 80 (298 + x) = 80 * 5 x = 80 * 5 - 298 x = 102 I think this kid is in trouble :(
*June 22, 2015*

**algebra**

first = x second = x+10 third = 2x-5 sum = 45
*June 22, 2015*

**physics**

20 g ( 4.18 J/g deg C )(30 deg C-10 deg C) = 1672 J which is closer to 1700 than to anything else on your list.
*June 22, 2015*

**MATH**

Henry x sister 12 friend 12 - 6 = 6 so gave away 12+6 = 18 so he was left with 2*18 = 36 so he had 36 + 18 = 54
*June 22, 2015*

**Math**

Needs a modern fuel efficient car, or a newer text book :)
*June 22, 2015*

**Math**

144.6/4 = miles per hour 144.6/12 = miles per gallon
*June 22, 2015*

**physics**

25 = .40 a
*June 22, 2015*

**Science**

2.34/12 = .195 .16/1 = .16 (I assume hydrogen atoms not molecules?) .46/14 = .0329 1.04/16 = .065 for every nitrogen atom we have .065/.0329 = 1.97 O and .195/.0329 = 5.9 C and .16/.0329 = 4.86 H C6 H5 N O2
*June 22, 2015*

**physics**

for part b kinetic energy at ground - F * h = potential energy at top (1/2) (1) (23)^2 - F (17.8)= 1*9.81*17.8 264.58 - 17.8 F = 174.6 F = 5.05 Newtons I get
*June 21, 2015*

**Calculus(math)**

To get distance from the velocity you must integrate.
*June 21, 2015*

**Physics**

circumference = 2 pi r = 19.48 meters a) 36/360 = .1 .1 * 19.48 = 1.948 meters b) angle in radians * r = distance 36 * 3.1 = 111.6 meters c) 36 * 19.48 = 701
*June 21, 2015*

**physics 1401**

-5 - -3 = -2 -4 - 8 = -12 sqrt (4 +144) = 12.2
*June 21, 2015*

**physics**

m g h = (435-205) h = (435-25)/( 30*9.81)
*June 21, 2015*

**physics**

initial Ke = (1/2)(54.5)(1.95)^2 = 104 J energy added = 80-265 = - 185 J so if no change in elevation final ke would be 104-185 = - 81 J actual final ke = (1/2)(54.5)(5.95)^2 = 965 J so the gravitational PE loss (dropped down to gain speed) = 965 + 81 = 1046 J or delta PE = -...
*June 21, 2015*

**physics**

work done by push = 154 * 6.4 J positive work done by friction = -50*9.81*.24*6.4 J negative work done by normal = work done by weight = ZERO because force perpendicular to displacement
*June 21, 2015*

**World War 2**

Google "peace in our time "
*June 21, 2015*

**physics**

oh well, I suppose I can pretend to know what the question is. v = vertical speed Vi = initial vertical speed so Vi = 10 sin 53.1 How long rising? v = Vi - g t = Vi - 9.81 t at top, v = 0 so tt = Vi/9.81 at the top (calling tt the top time) How high at top? h = 24 + Vi tt - 4....
*June 21, 2015*

**math**

Your initial velocity component up which you are calling Vo is 1750 sin 10 so Vo = 304 ft/s ( I can hardly believe you are using feet not meters but well here g will be 32 ft/s^2) Your distance down range, x = u t where your constant horizontal speed u = 1750 cos 10 (that is ...
*June 21, 2015*

**Math**

Oh and also it is imaginary for (2-x) negative or x > 2 In other words the new inverse curve is open to the left with a vertex at (2,-3)
*June 21, 2015*

**Math**

well, first of all that is a parabola as you know. If you invert it, it is likely to have two values of the ordinate for every value of the abscissa. In other words the inverse will not likely really be a function. However to do what you want to do, use x for y and y for x and...
*June 21, 2015*

**Chemistry**

nah, 10^23/10^23 = 1 perhaps write it as (6.70/6.02)(10^23/10^23) * 18.02
*June 21, 2015*

**Math 11 u**

Or now that I know the answer: w^2 + 4 w - 117 = 0 (w-9)(w+13) = 0
*June 21, 2015*

**Math 11 u**

w^2 + 4 w - 117 = 0 Do you know how to use the quadratic equation? w = [ -4 +/- sqrt (16 + 468) ] /2 w = -2 +/- (1/2) sqrt 484 ) w = -2 +/- (1/2)22 w = -2 +/- 11 use the + root w = 9 then L = 13 ============== check 9 * 13 = 117 sure enough
*June 21, 2015*

**Chemistry**

Fe = 56 2N =2*14 = 28 6O = 6*16 = 96 so the stuff is 180 grams/mol .555 * .650 = .361 mols present .361 * 180 = 65 grams
*June 21, 2015*

**Physics**

both go distance d car A takes time t car b takes time (t - 1) d = 50 t d = 60 (t - 1) so 50 t = 60 t - 60 10 t = 60 t = 6
*June 21, 2015*

**Typos, math, physics**

Would everyone who posted math and physics problems this morning please go back and check for typos? It is difficult to guess what you mean and we do not have your text book.
*June 21, 2015*

**Nobody knows**

You did not tell us: 1. radians per second or rpm or something about speed. 2. jow high the axis of the wheel is.
*June 21, 2015*

**chem**

http://www.google.com/search?q=potassium+carbonate+formula&ie=utf-8&oe=utf-8
*June 21, 2015*

**chem**

CO3-- is negative two In other words it has two more electrons than protons K + is plus one. in other words it is missing an electron To make it all come out a neutral solid salt you need two K ions for every one carbonate ion so K2CO3 GOOGLE potassium Carbonate https://www....
*June 21, 2015*

**physics**

kg * m/s * m/s = kg m^2/s^2 By the way force = mass * acceleration which is kg m/s^2 in Newtons force * distance = work which is energy in Joules so energy = kg m/s^2 * m = kg m^2/s^2
*June 20, 2015*

**Algebra**

The y axis intercept is when x = 0 Here when x = 0 y = (-3)^2(-9) = 9 * -9 = -81 The x intercepts are when y = 0 which is when x = 3 (just barely hits the axis) and when x = 9 On the right is when x is very large positive. That is y ---> x^2 (x) = x^3 rising on the left x ...
*June 20, 2015*

**homewrok**

(tagged/total) = (8/60)= 200 / x 2/15 = 200/x 1/15 = 100/x x = 1500
*June 20, 2015*

**Calculus**

Perhaps you mean x = delta x = 1 ??? y = 7 x^-1 dy/dx = 7 (-1)x^-2 = -7 x^-2 if x = 1 y = 7/1 = 7 dy/dx = -7 delta y = -7 delta x if delta x = 1 delta y = -7 Y + delta Y = 7-7 = 0 real answer y (2) = 7/2 = 3.5
*June 20, 2015*

**ALGEBRA**

let age = x x/4 + x/5 + x/3 + 13 = x LCD = 60 60 x/4 + 60 x/5 + 60 x/3 + 13*60 = 60 x 15 x + 12 x + 20 x + 13 * 60 = 60 x 47 x + 13 * 60 = 60 x 13 x = 13 * 60 x = 60
*June 20, 2015*

**physics**

It fell 100 meters. h = (1/2) g t^2 100 = 4.9 t^2 t = 4.52 seconds
*June 20, 2015*

**Physics**

yes If you were a ship designer you would know that for a model and full scale under gravitation v/sqrt(gL) is the same model and full scale. if you divide the lengths by 100, you divide the speeds by 10 Google Froude number - here : http://www.engineeringtoolbox.com/froude-...
*June 20, 2015*

**Physics**

The forces will certainly not be the same but much smaller on the model. The acceleration is the question. h = H/10^2 m = M/10^6 because volume is 1/100^3 V = sqrt (2 g H) v = sqrt (2 g h) so v = V/10 acceleration is velocity /time time is distance/velocity so acceleration = k...
*June 20, 2015*

**Physics**

mass = 9/g = 9/9.81 kg = .917 friction or other force holding it back = 15 Newtons so F - 15 = ma = .917 (a) but a = 14/4 so F = 15 + .917(14/4) = 18.2 N
*June 19, 2015*

**Physics**

F = m g down - 40 up = 10(9.81)-40 = 58.1 N down a = F/m = 58.1/10 = 5.81 m/s^2 down
*June 19, 2015*

**math**

Note Mathmate response to the question below titled Calculus AB
*June 18, 2015*

**math**

be careful with parentheses like use dy/dx= (x^2+3y^2)/ ( 2xy ) http://www.wolframalpha.com/widgets/view.jsp?id=e602dcdecb1843943960b5197efd3f2a y = +/- x (cx-1)^.5
*June 18, 2015*

**Math**

s = 2 f/3 s = 4 (f+5) /7 -------------------- 2 f/3 = 4 f/7 + 20/7 2*21 f/3 = 4*21 f/7 + 20*21 /7 14 f = 12 f + 60 2 f = 60 so f = 30 s = 2 f/3 = 20 ======================= check s/f = 20/30 = 2/3 yes s/(f+5) = 20/35 = 4/7 yes, it worked
*June 18, 2015*

**stats**

http://davidmlane.com/hyperstat/z_table.html
*June 18, 2015*

**Chemistry**

CH3CH2OH + 3O2 => 2CO2 + 3H2O CH3CH2OH is 2*C = 24 + 6*H = 6 + 1*O = 16 = 46 grams/mol so that is 775/46 = 16.85 mols of ethanol so we would get 2*16.85 = 33.7 mols of CO2 CO2 = 12+32 = 44 grams/mol 33.7 *44 = 1483 grams of CO2 Oh my, greenhouse galore
*June 18, 2015*

**Public speaking**

https://www.google.com/search?q=articulate+definition&ie=utf-8&oe=utf-8
*June 18, 2015*

**Public speaking**

I am having trouble articulating a reply.
*June 18, 2015*

**Math Trigonometry**

tan angle = 6/8 = .75
*June 18, 2015*

**science**

For example from that link: " Reason #1: Without wolves and other large predators, ecosystems can go haywire. A 2001 study (PDF) found that when wolves went extinct in Yellowstone, for example, the moose population ballooned to five times its normal size and demolished ...
*June 18, 2015*

**science**

Here, click through these 10 pictures http://www.motherjones.com/slideshows/2011/04/wolves-protect-climate-change/seated-gray-wolf-yellowstone
*June 18, 2015*

**science**

The animals the lynx eats would get more numerous. The plants and animals that those target animals eat would get scarcer. Whatever they in turn feed on multiplies. The effects work down from that top predator and equilibrium populations of everything in the forest changes. ...
*June 18, 2015*

**physics**

v = Vi - g t here Vi = 150 sin 30 = 75 m/s at top v = 0 0 = 75 - 10 t solve for t at top t = 7.5 seconds then if they ask for the height h = (1/2) g t^2 to fall from top = 5 * (7.5)^2 then if they ask for range u = 150 cos 30 range = u t = 150 cos 30 * 7.5 * 2 the 2 is because...
*June 18, 2015*

**Math (PLEASE HELP!)**

divide length dimension by sqrt 2 to get half the area
*June 18, 2015*

**Math (PLEASE HELP!)**

w(w+5) >/= 84 w^2 + 5 w - 84 >/= 0 solve for zero, anything bigger works w = [ -5 +/- sqrt(25 + 336) ]/ 2 w = [ -5 + 19 ]/2 = 7 then L = 12 so anything at least 7 by 12
*June 18, 2015*

**Math (PLEASE HELP!)**

parabola opens down (sheds water) when is it between the vertex and 22 feet? 16 t^2 - 42 t - 3.75 = -22 16 t^2 - 42 t + 18.25 = 0 t = [ 42 +/- sqrt (1764 - 1168) ] / 32 t = [ 42 +/- 24.4 ] /32 t = .55 to 2.07 seconds
*June 18, 2015*

**physics**

or in other words half the radius -->4 g then 4 times the earth mass --> another 4 times g
*June 18, 2015*

**physics**

mstudent = 810/9.81 = 82.6 kg THE MASS, m in kg, DOES NOT CHANGE WITH g, ONLY THE WEIGHT F = G * Mplanet* mstudent /r^2 on earth 810 = G Mearth * mstudent /rearth^2 on Nerdland F = G Mnerd *82.6 / rnerd^2 so F = G (4 Mearth) * 82.6 / (.25 rearth^2) F = 16 G Mearth * 82.6 /...
*June 18, 2015*

**PHYSICS**

(1/2) m Vi^2 + m g h = (1/2) m Vfinal^2 or Vfinal^2 = Vi^2 + 2 g h = 225 + 2 (9.81)(20) = 617.4 sqrt 617.4 = 24.8
*June 18, 2015*

**physics**

a - gravity down, air friction up b - friction force exerted on roadway by horseshoe, equal and opposite force exerted by horseshoe on roadway, horse then exerts pull on shaft, shaft pulls back on horse and forward on cart, roadway exerts friction force back on cart c - ...
*June 18, 2015*

**System of Equation**

That is substitution.
*June 18, 2015*

**physics**

As I said a few minutes ago, you try first.
*June 15, 2015*

**Physics**

delta L/L = (1.1*10^-5)(45) = 49.5 * 10^-5 meters/meter of hypothetical stretch that delta L/L is strain delta L/L = sigma/E which is stress/young's stress = 4.95*10^-4 * 2*10^11 = 9.9 *10^7 N/m^2 tension = stress * area =9.9*10^7 * 4*10^-6 = 396 N b) well we got 9.9*10^7 ...
*June 15, 2015*

**physics**

Just like the balloon A and B problem. I will be happy to review your results.
*June 15, 2015*

**physics**

Now Alex, enough already, draw picture with all forces. There is one, the weight F = - m g so F = m a = - m g so a = -g THE WHOLE TIME, NOT JUST AT TOP Now no more questions until you try yourself !!!!
*June 15, 2015*

**algebra 2**

GRAPH IT !!!!! when x = 5 , f(5) = 25 when x = 2 , f(2) = 4 check when x = -2 , f(-2) = -4 when x = 1 , f(1) = 5 check
*June 15, 2015*

**physics**

huh? 5 + 7.5
*June 15, 2015*

**physics**

well, do the power thing first v = 0 + a t v = Vi = 20 * 4 = 80 m/s at power cutoff at what height did the power stop? h = 0 + 0 t + (1/2)(20)(16) = 160 meters so we have Vi = 80 m/s at Hi = 160 meters now coast up v = Vi - g t at top v = 0 , using g = 9.8 0 = 80 - 9.8 t t = 8...
*June 15, 2015*

**algebra2**

well, let's look at the zeros first x(x^2-9) - 1(x^2-9) = 0 (x-1)(x-3)(x+3) = 0 so y = 0 for x = 1 and for x = 3 and for x = -3 that is three values of x for a single value of y, not a good symptom.
*June 15, 2015*

**Calculus**

The max is where |sin x| = 1, cos x = 0 the min is where sin x = 0, |cos x| = 1 but really all you really have to say is |sin x | </= 1 so |sin^2 x| </= 1 so max is 1 and that is when |sin x|=1
*June 15, 2015*

**Calculus**

You already did it. f(0) = 0 f(pi) = 1 etc, at the four points where the derivative is zero
*June 15, 2015*

**Calculus**

You mean cos x sin x = 0 when cos x = 0 or when sin x = 0 when cos x = 0, then sin x = 1 and you have a max when sin x = 0, then cos x = 1 and you have a min
*June 15, 2015*