Tuesday

July 28, 2015

July 28, 2015

Total # Posts: 21,552

**Math**

40 /(2/3) = 120/2 = 60
*July 7, 2015*

**Chemistry-History-ish**

Good except the first sentence is misleading. Those experiments did not discover "radioactivity". They were studies into the structure of matter as described in the problem statement. For discovery of radioactivity see "Madame Curie". for example : http://...
*July 7, 2015*

**Math**

LOL, draw an equilateral triangle with centroid at origin or a circle with center at origin and radius = 1. for the circle a it just gets to be a bigger circle (so it is similar) b same deal, smaller circle but similar. c try it, I think it will be kind of elliptical (do you ...
*July 7, 2015*

**Chemistry**

carbon monoxide This makes the difference clear between carbon monoxide CO and carbon dioxide CO2 You do not need to say mono carbon monoxide or mono carbon dioxide because they are both one carbon and there is no confusion.
*July 7, 2015*

**physics**

d omega / dt = alpha = (1400-428)/6.26 = 155 rad/s^2 which is angular acceleration part b theta = 428 t + (1/2)(155)t^2 but t is 6.26 so theta = 5722 radians which is part a
*July 7, 2015*

**Physics**

For example Fx = F dot i = |F|cos of angle to x axis
*July 7, 2015*

**Physics**

Components of vectors such as components of a force vector are also scalars. They are the dot product of the vector with the unit vector in the component direction.
*July 7, 2015*

**Physics**

I am inclined to disagree. Displacement is a vector with magnitude and direction. DISTANCE is the scalar magnitude of displacement. However Work, for example in Joules, is clearly scalar and has no direction. It is a dot product of force and displacement vectors and has no ...
*July 7, 2015*

**Physics**

255 cos 60 * 15 assuming that the force is at 60 degrees from the motion. 1912 Joules
*July 7, 2015*

**American History**

The colonists made the natives miserable, and they did not even know that the Europeans brought the diseases that killed most of them. See for example http://www.history.com/topics/native-american-history/king-philips-war
*July 7, 2015*

**physics**

V entry = a t = 6.3*4.1 = 25.83 m/s v = 25.83 + 6.3 t x = 25.83 t + (1/2)(6.3) t^2 for the second car x = 70.7 t so 70.7 t = 25.83 t + 3.15 t^2 3.15 t^2 - 44.87 t = 0 t (3.15 t -44.87) = 0 so they are at the same x at sthe start of course and at t = 44.87/3.15
*July 7, 2015*

**pysics**

Immediately after drop its vertical speed is zero, so no drag. therefore m a = m g and it accelerates down at 32 m/s^2 as it builds up speed and the chute deploys, the air drag increases at about proportional to speed squared until the drag force up equals the m g down and the...
*July 7, 2015*

**math**

You are welcome.
*July 7, 2015*

**math**

on your graph mark the point where x = 1 and y = -3 from there go right one and down one (slope of -1) and mark a second point. draw a line through those two points.
*July 7, 2015*

**math**

y = m x + b put in slope m y = -1 x + b put in point y = -2 where x = 1 -3 = -1(1) + b so b = -2 so y = -x -2
*July 7, 2015*

**Chemistry**

mass * ( heat of fusion + heat capacity * 100 + heat of vaporization)
*July 7, 2015*

**physics**

mg downward 30 N upward net downward = m g - 30 g is not in Newtons but in m/s^2. It is more like 9.81 m/s^2 on earth but ok, use 10 m/s^2 net downward = 5 kg ( 10 m/s^2) - 30 = 50 - 30 = 20 Newtons
*July 7, 2015*

**statistics**

Sure looks like .7 to me. The ones not in the window have nothing to do with your problem.
*July 7, 2015*

**science**

although it also has rotational energy Kinetic spin energy = (1/2)I omega ^2 = (1/2)(2/5) (.2)(R^2) omega^2 but v = R omega so add (1/2) (2/5)(.2) (25)
*July 7, 2015*

**science**

(1/2) m v^2 = .5*.2*25 Joules
*July 7, 2015*

**physics**

west inertia before = west inertia after 2000 * 20 = 5000 * Vwest south inertia before = south inertia after 3000 * 20 = 5000 * Vsouth V = sqrt (Veast^2+Vsouth^2) tangent of angle west of south = Vwest/Vsouth compass course = 180 + that angle
*July 7, 2015*

**Math**

.2*2 + .3*1 -.3*2 -.2*0 .4 + .3 -.6 - 0 .1 I agree
*July 5, 2015*

**American history**

............I have already intimated to you the danger of parties in the State, with particular reference to the founding of them on geographical discriminations. Let me now take a more comprehensive view, and warn you in the most solemn manner against the baneful effects of ...
*July 5, 2015*

**Calculus**

dy/dx = slope = 2*5 x - 4 + 0 The 12 has no effect on the slope The slope is a straight line with y intercept of -4 and slope of 10 The 5 is half the slope of the derivative
*July 5, 2015*

**math**

5,747 * 1.021^n = 36,000,000 1.021^n = 36,000,000/5,747 = n = log (36,000,000 / 5,747)/log 1.021 = 421 ============================ check 1.021^421 = 6307 6307*5,747,000 = 3.6*10^10 = 3.6*10,000,000,000 =36,000,000,000 sure enough
*July 5, 2015*

**science**

weight * tan 4 = m a m g tan 4 = m a a = g tan 4
*July 5, 2015*

**maths**

LOL, should have checked that !
*July 5, 2015*

**maths**

We know that (x-sqrt 2) is a factor 6 x^3 + 2 x^2 - 10 x -4 sqrt 2 = 0 (x-sqrt 2)( a x^2 + b x + c) = 0 well, c better be 4 (x-sqrt 2)(a x^2 + b x + 4) = 0 now I will use distributive property to split this up x (a x^2 + b x + 4) -sqrt 2 (a x^2 + b x + 4) = 0 x terms: 4 x - b ...
*July 5, 2015*

**Math**

The first roll has no effect what so ever on the results of the second roll. They are independent events. Dependent events are those where the first outcome has an effect on the second. For example if you have two green balls and two red balls in a hat. The probability of ...
*July 5, 2015*

**physics**

There is no such thing as a force of 2 kg, sorry
*July 5, 2015*

**Math**

x^2 = t^2 cos^2 y^2 = t^2 sin^2 x^2 + y^2 = t^2(cos^2+sin^2) = t^2 but t^2 = z^2 so x^2+y^2 = z^2
*July 5, 2015*

**math**

36 + .2(450-100) assuming one day
*July 4, 2015*

**physics**

oh max acceleration magnitude = A w^2 = 5.6*10^-7 * (5040)^2
*July 4, 2015*

**physics**

harmonic motion with w = 2 pi *frequency or 2 pi/period y = A sin w t dy/dt = v = A w cos w t d^2y/dt^2 = a = -A w^2 sin wt = -w^2 y here v max = Aw = 2.82*10^-3 and A = 5.6*10^-7 so w = 2 pi f = 2 pi/T = 2.82/5.6 * 10^4 = .504*10^4 = 5040 radians/s f = 5040/2pi = 801 Hz T = 1...
*July 4, 2015*

**physics**

You are welcome.
*July 4, 2015*

**physics**

F = k x k = 82/.0191 F = (82/.0191) * .0520
*July 4, 2015*

**phys**

(I wonder if whoever gave you this problem really thought out the implications of the landing :)
*July 4, 2015*

**phys**

h = Hi + Vi t - 4.9 t^2 assume the road was level so Vi = 0 1.5 = 20.2 + 0 - 4.9 t^2 4.9 t^2 = 18.7 t = 1.95 seconds in the air to fall 18.7 meters so how far did he go horizontal in those 1.95 seconds? d = u t 60 = u * 1.95 u = 30.7 meters/second horizontal for the whole jump...
*July 4, 2015*

**science 207 lab wk 5**

How on earth would we know what is in wk 5 of science 207? We are not at your school or perhaps even in your country.
*July 4, 2015*

**Science**

4.9 t^2
*July 4, 2015*

**Science Help Not sure**

Ui = initial speed = 126*10^3/3600 = 35 m/s 65-126 = -61*10^3 meters / 3600 seconds = -16.94 m/s speed change -16.94/8 = -2.12 m/s^2 acceleration d = Ui t - (1/2) a t^2 = 35*8 -(1/2)(2.12)(64) = 212 m so A
*July 4, 2015*

**Science**

v = a t hey, try some of these yourself !
*July 4, 2015*

**Physics**

Vi up = 15 sin 30 = 7.5 m/s initially u = 15 cos 30 = 13 m/s forever Hi = 40 then h = Hi + Vi t - 4.9 t^2 0 = 40 + 7.5 t - 4.9 t^2 or 4.9 t^2 - 7.5 t - 40 = 0 t = [ 7.5 +/- sqrt(56.25 + 784) ] / 9.8 use + root of course t = 3.72 seconds then v = Vi - 9.8 t = 7.5-36.5 = -29 m/s...
*July 4, 2015*

**physics**

3 sin thete = 2 theta = 41.81 V across = 3 cos theta = 2.24 mi/hr (1/4)/2.24 = .112 hr = 6.7 minutes He has zero velocity parallel to the shore (that is the whole point) However he has speed of 2.24 mi/hr perpendicular to the shore.
*July 4, 2015*

**Physics**

well, I suppose they both have the same acceleration, call it a The total mass is 5000 kg The total force on the system is 6000 N so a = 6000/5000 = (6/5) m/s^2 Now how much of that is on the truck? F = 3000 a = 3000 (6/5) = 3600 Newtons from the car on the truck so the force ...
*July 3, 2015*

**physics**

All yo can really find in this world is DIFFERENCES in potential energy. In this case, whoever wrote the question probably expected you to define zero potential at the FLOOR so the h you use for part 1 which is 6.5 -2.5 = 4 is NOT the h you use for part 2 for part 2, use the ...
*July 3, 2015*

**physics**

LOL, it takes time, it is almost midnight, and I have to work tomorrow.
*July 2, 2015*

**physics**

v = omega r 1. 6.12 * 2.20 = 13.464 m/s 2. 6.12 * 15.2 = 93.024 3. 6.12 * 3.15 = 19.278 (1/2) m v^2 1. .5 * 6.36 * 13.464^2 = 577 Joules 2. you can do the next two 3. add them I = m r^2 1. 6.36 (2.2)^2 = 30.8 2. you can do 3. you can do add them for total I Ke = (1/2) I omega^...
*July 2, 2015*

**physics**

There are only two horizontal forces in this problem, at the wall and at the ground. Therefore they are equal and opposite, call the magnitude F now balance vertical forces 886 + 350 = force down = 1236 N that is therefore the normal force up at the ladder base the max ...
*July 2, 2015*

**math**

4 = 2^2 so (2^2)^(x+2) = 2^x but (a^b)^c = a^(bc) so 2^(2x+4) = 2^x 2x+4 = x x = -4
*July 2, 2015*

**math**

Now you can solve what I gave you for x which is the pounds of nuts with cashews.
*July 2, 2015*

**math**

5 t^2 - 7 t - 1 = 0 t = [ 7 +/- sqrt(49+20) ]/ 10 t = [ 7 +/- sqrt(69) ] / 10
*July 2, 2015*

**math**

3.95 x + 1.15 = 1.70 3.95 x = .55 x = .139 yes then .5 - x = .361 ------------------ check 6.25 * .139 = .869 2.30 * .361 = .830 ------------------- add ****** .5 lbs = 1.699 or in other words 1.70
*July 2, 2015*

**math**

x with cashews costs 6.25 x (.5-x) with peanuts costs 2.30 (.5-x) so 6.25 x + 2.30(.5-x) = 1.70
*July 2, 2015*

**Math**

if she works 40 hours per week (we are just guessing that), then she worked 80 hours for $383 383/80 = $4.7875 per hour
*July 2, 2015*

**Math**

The y intercept is where the line hits the y axis, in other words when x = 0 that means that in the equation of the line y = m x + b the y intercept is where x = 0 and y = b saying a point is on -3 and the other on + 5 does not help me You have to say for example at one point ...
*July 2, 2015*

**Finite**

maximize p = 8x + 10y subject to .6x + .45y <= 400 .4x + .55y <= 300 =============================== Vertex Lines Through Vertex Value of Objective (566.666667,133.333333) .6x+.45y = 400; .4x+.55y = 300 5866.666667 Maximum (666.666667,0) .6x+.45y = 400; y = 0 5333.333333...
*July 2, 2015*

**Finite**

http://www.zweigmedia.com/RealWorld/LPGrapher/lpg.html
*July 2, 2015*

**Finite**

cc = .6 x + .45 y </= 400 rb = .4 x + .55 y </= 300 income = i = 8 x + 10 y objective, maximize graph those functions, check the corners
*July 2, 2015*

**Finite Math**

well, in that first column I would like to see 1 0 0 so I would multiply row 1 by 2 subtract the result from row two and put that result where row 2 is then I would multiply row 1 by 3 instead of by 2 and subtract the result from row three, placing the result in row three.
*July 2, 2015*

**Applied Mathematics ( Mechanices**

a ) m g b ) m(g+5) c ) m(g-5) on earth g is about 9.81 m/s^2
*July 2, 2015*

**physics**

the braking force is opposite to the direction of motion, so we are doing negative work on the train delta W is negative Are we putting heat into the train? I think not. In fact heat is going out into the air as the brakes heat up. delta Q is negative So I suspect that the ...
*July 2, 2015*

**mathematics**

0.400 * 6.00 = $2.40
*July 2, 2015*

**Physics**

a = dv/dt = 4 i + 14 t F = m a 40 = 4.6 sqrt (4^2 + 14^2 t^2) (40/4.6)^2 = 16 + 196 t^2 solve for t use that t to get v and a Then v dot a = |v||a| cos theta
*July 2, 2015*

**Physics**

tension T force F horizontal vertical: T cos 32.9 = m g horizontal: T sin 32.9 = F
*July 2, 2015*

**algebra**

or ln (2-x) = 14 e^{ln(2-x) = 2-x so 2-x = e^14 x = 2 - e^14 x = - 1202602
*July 1, 2015*

**Differential Equation**

hmmm, not sure but dy/dx = [(1-y^2)/(1-x^2) ]^.5 dy/(1-y^2)^.5 = dx/(1-x^2)^.5 let y = sin p let x = sin r dy = cos p dp and dx = cos r dr cos p dp/cos p = cos r dr/cos r dp = dr
*July 1, 2015*

**Basic electrical engineering**

electron charge = e in coulombs i = how many coulombs pass a point in a second 65.5 coulombs/second = e * electrons per unit volume * area *length they move in one second which is .0153 inched I think I need the density of electrons in electrons per cubic inch
*July 1, 2015*

**Math**

8 a + 8.0 c = 72 8 a + 4.5 c = 58 ----------------- subtract 3.5 c = 14 c = 4 so a = 5
*July 1, 2015*

**Calculus Derivative**

let z = x^x y = e^z dy/dz = z e^z = x^x (e^x^x) dy/dx = dy/dz * dz/dx so we need dz/dx when z = x^x look here http://www.analyzemath.com/calculus/Differentiation/first_derivative.html for dz/dx = (ln x + 1) x^x so x^x ( e^x^x) (ln x + 1) x^x =x^2x e^x^x (ln x + 1)
*July 1, 2015*

**Algebra 1**

.08*12 + .20*x = .16 (12+x)
*July 1, 2015*

**Chem 105**

P1V1/T1 = P2V2/T2 750 * 36 /(273+10) = P2 * 15 /(273+78)
*July 1, 2015*

**Math**

10!/12! = 1/(12*11) 7!/5! = 7*6 7*6 /(12*11) = 7/22
*July 1, 2015*

**calc**

We agree, if that is indeed the question :)
*July 1, 2015*

**calc Huh??**

do you mean product of x and y? dy/dx = 8 x y or do you mean dy/dx = 8 x / y or what ? if the latter then y dy = 8 x dx y^2/2 = 8 x^2/2 + C y^2 - 8 x^2 = constant
*July 1, 2015*

**Geography**

In fact, just Angles, Saxons, Danes and Norse including former Vikings from Normandy in France are worth a few books covering their effect on culture and settlement of England :) Are you writing a PhD dissertation ?
*July 1, 2015*

**Geography**

This question is out of control !!! I do not know where to start. Perhaps divide up into regions of Europe: 1. Eastern Med and Black Sea - Greece, Balkans 2. Western Med - Italy(Etruscan, Roman), French Med coast, Spain 3. Atlantic coast, southern - Portugal, Basques, Frence, ...
*July 1, 2015*

**algebra**

10 * 2^(4 x - 5) = 41 ? 2^(4 x - 5) = 4.1 agree ln 2^(4 x - 5) = (4x-5) ln 2 = ln 4.1 agree 4 x - 5 = ln 4.1 / ln 2 = 2.036 4 x = 7.036 x = 1.76
*July 1, 2015*

**Maths**

(x+11)(x+8) = 208 x^2 + 19 x + 88 = 208 x^2 + 19 x - 120 = 0 (x+24)(x-5) = 0 so five
*July 1, 2015*

**math in distress**

LOL, English units bother me almost as much as the confusion between bearing and heading in mathematics texts :)
*July 1, 2015*

**math in distress**

Metric spoils all the fun. Remember: 1 slug = 1 pound/g = (1/32.174049)pounds on the surface of earth only.
*July 1, 2015*

**Statistics**

This might help: http://davidmlane.com/hyperstat/z_table.html
*June 30, 2015*

**typo**

2 inches = 1/6 foot
*June 30, 2015*

**math**

volume of stuff is 2 inches times (area of outer circle - area of inner circle) 22 inches = 1/6 foot 1 yard^3 = 27 ft^3 so 27 = (1/6)(pi)(R^2 - 5^2) solve that for R then width of path = R-5 in feet
*June 30, 2015*

**Chemistry**

You are welcome. Good luck.
*June 30, 2015*

**Chemistry**

I prefer that to your cathode ray tube, but you better add explanation of why some are falling and some are rising :)
*June 30, 2015*

**Chemistry**

I think it might be a good idea to read up on the Millikan oil drop experiment. For example: http://felix.physics.sunysb.edu/~allen/252/PHY251_Millikan.html
*June 30, 2015*

**physics**

East velocities + momentum before = 0 so momentum after = 0 1 * 8 + 5 * v = 0 v = 8/5 west
*June 30, 2015*

**mathematics :geometric progression**

k-3 = a r a = 2k-4 r^2 a = 4k-3 ------------------- r= (4k-3)/(2k-4) = (2k-4)/(k-3) so (2k-4)^2= (k-3)(4k-3) 4 k^2 -16 k + 16=4 k^2 - 15k +9 -k = -7 k = 7 go back and find a and r
*June 30, 2015*

**Differential calculus**

I think you probably mean V = Vo e^(-t/RC) where Vo is 300 volts and the chrge is discharged through the resistor here 1/RC = 1/(.12*4) = 2.08 so V = 300 e^-2.08 t dV/dt = -2.08(300) e^-2.08 t = -625 e^-2.08 t volts/second obviously when t = 0 this is -625 you can put in .5 or...
*June 30, 2015*

**Math**

distance = rate * time :)
*June 30, 2015*

**Physics 12-grade**

If W1 = f(x1,y1,z1) and W2 = f(x2,y2,z2) then the work from point 1 to point two is W2-W1 the work going back is W1 - W2 the net work for the round trip is zero. That is the point. If you can define potential as a function of position, the field is conservative. It is really a...
*June 30, 2015*

**Physics 12-grade**

That is the whole point of a potential field. It does not matter you you get from point x1,y1,z1 to point x2,y2,z2 The work done is the same by any path. It may not seem that way if you are taking different trails, steep ones that go up and down and easy ones with a constant ...
*June 30, 2015*

**Physics 12-grade**

If the work done is a function of x y and z, then the force is conservative.
*June 30, 2015*

**statistics**

Now wait a minute. You are asking a lot of questions some of which I am sure you can do. For example in number 31, it is clear that only 1,3,and 7 are in both A and B Please do not ask us questions without trying yourself and posting your attempt. I do not have your font for ...
*June 30, 2015*

**math**

I guess you mean that 70% studied? If so then if there were 100 students: 70 studied, 66.5 passed 30 did not study, 18 passed so out of 100 students 84.5 pass so .845
*June 30, 2015*

**math**

as n---> oo the term -----> n^2/(4n) or n/4 or oo so for sure it does not convergerge. n=1, 1/5 etc down to n = 5, 25/21 now try n = 10 100/41 , starting to climb
*June 30, 2015*

**physics**

You are welcome.
*June 29, 2015*

**physics**

(1/2) m v^2 = m g h v^2 = 2 gh v = sqrt (2 g h) = sqrt(2*9.81*4) = 8.86 m/s
*June 29, 2015*

**physics**

u = 5 m/s forever v = -g t h = 5 - 4.9 t^2 h = 0 at ground so 4.9 t^2 = 5 t = 1.01 seconds so v = - 9.81 * 1.01 = - 9.91 m/s speed = sqrt (5^2 + 9.91^2) = 11.1 m/s in other words I dissagree with jzee11
*June 29, 2015*