Tuesday

September 30, 2014

September 30, 2014

Total # Posts: 583

**chemistry**

If He(g) has an average kinetic energy of 7590 J/mol under certain conditions, what is the root mean square speed of F2(g) molecules under the same conditions?
*September 28, 2014*

**chemistry**

Hydrogen gas produced by this reaction is typically collected via water displacement, during which time the hydrogen gas becomes saturated with water vapor. If 238.4 mL of gas with a total pressure 1.27 atm was collected via water displacement at 29.4 °C, what is the ...
*September 27, 2014*

**chemistry**

Imagine there is a tank of unknown gas that contains 53.31% carbon, 35.51% oxygen, and 11.18% hydrogen by mass. At 35.0 °C and 0.470 bar, 2.0 L of the gas has a mass of 3.3 g. Using this information, answer the following questions. a.) What is the empirical formula of the ...
*September 27, 2014*

**chemistry**

A 8.50-g sample of solid AlCl3·6H2O was heated such that the water turned to steam and was driven off. Assuming ideal behavior, what volume would that steam occupy at 1.00 atm and 100.0 °C?
*September 27, 2014*

**chemistry**

Air is 78.1% nitrogen, 20.9% oxygen, and 0.934% argon by moles. What is the density of air at 22 °C and 760 torr? Assume ideal behavior.
*September 27, 2014*

**Biology**

Why does biomass decrease as we move up the biomass pyramid?
*September 27, 2014*

**science**

Is it possible that free Internet content might one day replace textbooks?
*September 13, 2014*

**physics **

A skydiver weighs 158 lb. When the skydiver reaches terminal speed, how much air drag does the skydiver experience?
*September 9, 2014*

**math**

2/5+1/10 is 5/10. But in my book it states that the answer is 7/15, without an explanation.
*August 15, 2014*

** math**

A jar contains four blues marbles and two green marbles. Without looking, two marbles are drawn from the jar. What is the probability that two marbles with the same color will be selected?
*August 15, 2014*

**Chemistry**

Orange juice clams that 200ml of their product contains 2.5 times the average daily allowance of Vitamin C. Calculate the average daily allowance of vitamin c (in mg) if the orange juice contains 0.040% (w/v) of vitamin C.
*July 28, 2014*

**math **

The product of two numbers is 35. one of the numbers is n, what expression represents the other number?
*July 9, 2014*

**science**

LIFE
*June 16, 2014*

**chem**

Three of the primary components of air are carbon dioxide, nitrogen, and oxygen. In a sample containing a mixture of only these gases at exactly one atmosphere pressure, the partial pressures of carbon dioxide and ni- trogen are given as PCO2 = 0.285 torr and PN2 = 593.297 ...
*May 30, 2014*

**chem**

A gas occupying 10 mL at standard conditions is heated to 10◦C while the pressure is reduced to 0.92114 atm. What is the new volume occupied by the gas? Answer in units of mL
*May 30, 2014*

**Chemistry**

Did I break this up correctly? NaHclO3 breaks into Na+ and HClO3-, and that further breaks into H+ and ClO3-
*May 28, 2014*

**chemistry**

Is that the right way to break down NaHClO3?
*May 28, 2014*

**chemistry**

NaHclO3 breaks into Na+ and HClO3-, and that further breaks into H+ and ClO3-, is that right?
*May 28, 2014*

**chemistry**

How did you get .99 for the molality value?
*May 27, 2014*

**chemistry**

Instead of NaCl, can I pick any other salt, as long as it has a Van't Hoff factor/ i value of 2?
*May 27, 2014*

**chemistry**

Something that will lower the freezing point of water to -3.7 degrees Celsius if one mole were placed in 1000 grams of water? To solve this I know I have to use the equation Tf= IKfm, Tf= 3.7, but how I go about the problem there if I don't know Kf or the the mole of ...
*May 27, 2014*

**chemistry**

M= mol/L, so it would be Liters x(mol/Liters), liters cancels out with liters so you are left with the amount of mols
*May 27, 2014*

**English**

Thank you, Ms. Sue! Housing is a very important issue.
*May 27, 2014*

**English**

Please Help!!! I just need some ideas to right a short essay. I've already though of allergies as one problem. Language Arts Essay: A law requiring everyone to have a pet might cause serious problems for some people. What problems do you thinks such a law could cause? In ...
*May 27, 2014*

**Chemistry**

What element(s) are more polarizable than oxygen? How can you tell? Wouldn't fluorine be most polarizable, because it is the most electronegative?
*May 26, 2014*

**Maths Probability**

5) 8
*May 20, 2014*

**math**

what is tan 3pi/4
*May 19, 2014*

**Maths Probability**

I am in need of the above soln if anybody knew solution please give answers...
*May 15, 2014*

**Algebra**

Let k(x) = -3.7e^0.8x + 8.2 Find the asymptote, y-intercept, k(-2), and k(6.25) 1. Asymptote = 2. Y - intercept = 3. k(-2) = (leave answer in terms of e) 4. k(6.25) = (leave answer in terms of e)
*May 12, 2014*

**History Re-post **

1) The essential question for the last few lessons asks "How did Canada seek to establish economic security and social justice from the period of the depression to the patriation of the Constitution? What kind of economic security did the Canadians seek? What kind of ...
*May 9, 2014*

**history **

1) The essential question for the last few lessons asks "How did Canada seek to establish economic security and social justice from the period of the depression to the patriation of the Constitution? What kind of economic security did the Canadians seek? What kind of ...
*May 9, 2014*

**Probability**

We are given the following statistics about the number of children in the families of a small village. There are 100 families: 10 families have no children, 40 families have 1 child each, 30 families have 2 children each, 10 families have 3 each, and 10 families have 4 each. ...
*May 1, 2014*

**Probability**

A single dot is placed on a very long length of yarn at the textile mill. The yarn is then cut into pieces. The lengths of the different pieces are independent, and the length of each piece is distributed according to the same PDF fX(x). Let R be the length of the piece that ...
*May 1, 2014*

**Probability**

Consider a Poisson process with rate λ. Let N be the number of arrivals in (0,t] and M be the number of arrivals in (0,t+s], where t>0,s≥0. In each part below, your answers will be algebraic expressions in terms of λ,t,s,m and/or n. Enter 'lambda' ...
*May 1, 2014*

**Probability**

All ships travel at the same speed through a wide canal. Each ship takes t days to traverse the length of the canal. Eastbound ships (i.e., ships traveling east) arrive as a Poisson process with an arrival rate of λE ships per day. Westbound ships (i.e., ships traveling ...
*April 30, 2014*

**Probability**

Can someone please answer?
*April 30, 2014*

**Probability**

In parts 1, 3, 4, and 5 below, your answers will be algebraic expressions. Enter 'lambda' for λ and 'mu' for μ. Follow standard notation. Shuttles bound for Boston depart from New York every hour on the hour (e.g., at exactly one o'clock, two o&#...
*April 30, 2014*

**Probability**

Suppose that you have two laptops, both of which you begin using at time 0. Each laptop will eventually fail, and we model each one's lifetime as exponentially distributed with the same parameter λ. The lifetimes of the two laptops are independent. One of the laptops ...
*April 30, 2014*

**Probability**

Fred is giving away samples of dog food. He makes visits door to door, but he gives a sample away (one can of dog food) only on those visits for which the door is answered and a dog is in residence. On any visit, the probability of the door being answered is 3/4, and the ...
*April 30, 2014*

**Astronomy**

12435
*April 25, 2014*

**Probability**

For any given flight, an airline tries to sell as many tickets as possible. Suppose that on average, 10% of ticket holders fail to show up, all independent of one another. Knowing this, an airline will sell more tickets than there are seats available (i.e., overbook the flight...
*April 23, 2014*

**Probability**

Let X be a continuous random variable. We know that it takes values between 0 and 3, but we do not know its distribution or its mean and variance. We are interested in estimating the mean of X, which we denote by h. We will use 1.5 as a conservative value (upper bound) for the...
*April 23, 2014*

**Probability**

For each of the following sequences, determine the value to which it converges in probability. (a) Let X1,X2,… be independent continuous random variables, each uniformly distributed between −1 and 1. Let Ui=X1+X2+⋯+Xii,i=1,2,…. What value does the ...
*April 23, 2014*

**Probability**

Let Θ be an unknown random variable that we wish to estimate. It has a prior distribution with mean 1 and variance 2. Let W be a noise term, another unknown random variable with mean 3 and variance 5. Assume that Θ and W are independent. We have two different ...
*April 20, 2014*

**Probability**

Consider a fire alarm that senses the environment constantly to figure out if there is smoke in the air and hence to conclude whether there is a fire or not. Consider a simple model for this phenomenon. Let Θ be the unknown true state of the environment: Θ=1 means ...
*April 20, 2014*

**Probability**

Manhole explosions (usually caused by gas leaks and sparks) are on the rise in your city. On any given day, the manhole cover near your house explodes with some unknown probability, which is the same across all days. We model this unknown probability of explosion as a random ...
*April 20, 2014*

**Probability**

???
*April 20, 2014*

**Probability**

Let N,X1,Y1,X2,Y2,… be independent random variables. The random variable N takes positive integer values and has mean a and variance r. The random variables Xi are independent and identically distributed with mean b and variance s, and the random variables Yi are ...
*April 20, 2014*

**Probability**

Let X be a random variable that takes non-zero values in [1,∞), with a PDF of the form fX(x)=⎧⎩⎨cx3 if x≥1, 0,otherwise. Let U be a uniform random variable on [0,2]. Assume that X and U are independent. What is the value of the constant c? c= P(X...
*April 20, 2014*

**Probability**

Let U, V, and W be independent standard normal random variables (that is, independent normal random variables, each with mean 0 and variance 1), and let X=3U+4V and Y=U+W. Give a numerical answer for each part below. You may want to refer to the standard normal table. What is ...
*April 20, 2014*

**Statistics**

1. For the following research question, specify the parameter and give the null and alternative hypotheses. "Is there a difference in the proportions of male and female college students who smoke cigarettes? 2. For the following research question, specify the parameter ...
*April 6, 2014*

**Probability**

The random variable X is uniformly distributed over the interval [θ,2θ]. The parameter θ is unknown and is modeled as the value of a continuous random variable Θ, uniformly distributed between zero and one. Given an observation x of X, find the posterior ...
*April 3, 2014*

**Probability**

Let N be a geometric r.v. with mean 1/p; let A1,A2,… be a sequence of i.i.d. random variables, all independent of N, with mean 1 and variance 1; let B1,B2,… be another sequence of i.i.d. random variable, all independent of N and of A1,A2,…, also with mean 1 and ...
*April 3, 2014*

**Probability**

Let X=U+W with E[U]=m, var(U)=v, E[W]=0, and var(W)=h. Assume that U and W are independent. The LLMS estimator of U based on X is of the form U^=a+bX. Find a and b. Express your answers in terms of m, v, and h using standard notation. a=- unanswered b=- unanswered Suppose we ...
*April 3, 2014*

**Probability**

Caleb builds a particle detector and uses it to measure radiation from a remote star. On any given day, the number of particles, Y, that hit the detector is distributed according to a Poisson distribution with parameter x. The parameter x is unknown and is modeled as the value...
*April 3, 2014*

**Probability**

We have k coins. The probability of Heads is the same for each coin and is the realized value q of a random variable Q that is uniformly distributed on [0,1]. We assume that conditioned on Q=q, all coin tosses are independent. Let Ti be the number of tosses of the ith coin ...
*April 3, 2014*

**probability**

The lifetime of a type-A bulb is exponentially distributed with parameter λ. The lifetime of a type-B bulb is exponentially distributed with parameter μ, where μ>λ>0. You have a box full of lightbulbs of the same type, and you would like to know ...
*April 3, 2014*

**Probability**

Let T1,T2,…,Tn be i.i.d. observations, each drawn from a common normal distribution with mean zero. With probability 1/2 this normal distribution has variance 1, and with probability 1/2 it has variance 4. Based on the observed values t1,t2,…,tn, we use the MAP rule ...
*April 2, 2014*

**probability**

The vertical coordinate (“height") of an object in free fall is described by an equation of the form x(t)=θ0+θ1t+θ2t2, where θ0, θ1, and θ2 are some parameters and t stands for time. At certain times t1,…,tn, we make noisy ...
*April 2, 2014*

**Probability**

Let Θ be a Bernoulli random variable that indicates which one of two hypotheses is true, and let P(Θ=1)=p. Under the hypothesis Θ=0, the random variable X is uniformly distributed over the interval [0,1]. Under the alternative hypothesis Θ=1, the PDF of X ...
*April 2, 2014*

**Probability**

Alice has two coins. The probability of Heads for the first coin is 1/3, and the probability of Heads for the second is 2/3. Other than this difference, the coins are indistinguishable. Alice chooses one of the coins at random and sends it to Bob. The random selection used by ...
*April 2, 2014*

**Probability**

A defective coin minting machine produces coins whose probability of Heads is a random variable Q with PDF fQ(q)={3q2,0,if q∈[0,1],otherwise. A coin produced by this machine is tossed repeatedly, with successive tosses assumed to be independent. Let A be the event that ...
*April 2, 2014*

**Biology**

Why does an increase in light intensity cause the rate of photosynthesis to increase?
*March 26, 2014*

**Math**

Thank you Ms. Sue.
*March 20, 2014*

**Math**

4. Your article will be featured on the front page of the World section of the newspaper, as well as on-line. The article is to be placed in the shaded section below, which measures 4 inches wide by 9 inches long (not drawn to scale). Your editor has stated that your graph is...
*March 20, 2014*

**math**

Thank you Steve. That was my thinking as well. Appreciate it!!
*March 20, 2014*

**math**

Date US Population Jul 1, 2012 313.85 million Jul 1, 2011 311.59 million Jul 1, 2010 309.35 million Jul 1, 2009 306.77 million Jul 1, 2008 304.09 million Jul 1, 2007 301.23 million Jul 1, 2006 298.38 million Jul 1, 2005 295.52 million Jul 1, 2004 292.81 million Jul 1, 2003 ...
*March 20, 2014*

**Math**

Check please. Bar chart for each one because you have the values up the left side and item listed/categorized along the bottom for a more reader friendly chart for the data.
*March 20, 2014*

**Math**

20146/1650=12.21%
*March 20, 2014*

**physics**

What is the gravitational field strength at a height h above the surface of the Earth? R is the radius of the earth gR2(R+h)2 gR(R+h) g(R−h)R g(R−h)2R2 2 The instrument used for experimental determination of the value of the universal gravitational constant G is ...
*March 14, 2014*

**physics**

An object is thrown upward from the edge of a tall building with a velocity of 10 m/s. Where will the object be 3 s after it is thrown? Take g=10ms−2
*March 14, 2014*

**Physics**

Similarities between distance and displacement similarities between speed and velocity
*February 18, 2014*

**Grammar**

I thought it was natural to use "her", but I guess it is a common mistake.
*January 26, 2014*

**Mathh**

A certain state taxes the first $400,000 in property value at a rate of 1%; all value over $400,000 is taxed at 1.75%. Find a piecewise-defined function T that specifies the total tax on a property valued at x dollars. (Simplify your answer completely.) 0.01x if 0<x<400,...
*January 21, 2014*

**PHYSICS**

Can someone teach us how to do b,c?
*January 11, 2014*

**PHYSICS(help)**

did someone how to do 3,5,6b....?
*January 10, 2014*

**Engineering**

Thank you. I can find it now. But can you tell me how to do 2d,e , please?
*December 15, 2013*

**Engineering**

yes, I know...but I don't know how to find n and eta? can you teach me how to find it?
*December 15, 2013*

**Engineering**

how are about b,c? can you calculate it?
*December 15, 2013*

**Engineering**

In the process of electrolysis, electrical power is used to separate water into oxygen and hydrogen molecules via the reaction: H2O --> H2 + ½O2 This is very much like running a hydrogen fuel cell in reverse. We assume that only the activation potential for the ...
*December 15, 2013*

**Engineering**

Here we consider instead dissolving guns (which we will assume are pure iron) with sulfuric acid. Fe+H2SO4->FeSO4+H2 The characters realize that their hideout has been discovered by the police and they still have a last handgun that weighs 0.25 kg to dissolve. The cops will...
*December 15, 2013*

**Engineering**

Here we consider instead dissolving guns (which we will assume are pure iron) with sulfuric acid. Fe+H2SO4->FeSO4+H2 It is apparent that they must use an outside source of electrical power to drive the dissolution of the iron. They use a small current so that the ...
*December 15, 2013*

**Astronomy help**

I have already solve the problems in many time, but still cannot get the correct answer, can someone kindly help me to solve the problem, please? 1. Suppose the Moon is at a (center-to-center) distance D from Earth. Find an exact expression for the magnitude of the tidal force...
*December 12, 2013*

**Language arts help!!**

You don't learn anything by just copying answers.
*December 10, 2013*

**Physics Classical Mechanics**

You are holding a ball of mass m2 in your hand. In this problem you will solve for the upward force T⃗ that the tendon of your biceps muscle exerts to keep the forearm horizontal and the downward force F⃗ that the upper arm exerts on the forearm at the elbow joint...
*November 26, 2013*

**Physics Classical Mechanics**

A person of mass m2= 85.0 kg is standing on a rung, one third of the way up a ladder of length d= 3.0 m. The mass of the ladder is m1= 15.0 kg, uniformly distributed. The ladder is initially inclined at an angle θ= 35.0∘ with respect to the horizontal. Assume that ...
*November 26, 2013*

**Physics Classical Mechanics**

A uniform steel beam of mass m1= 300.0 kg is held up by a steel cable that is connected to the beam a distance L= 5.0 m from the wall, at an angle θ= 40.0∘ as shown in the sketch. The beam is bolted to the wall with an unknown force F⃗ exerted by the wall on ...
*November 26, 2013*

**Physics Classical Mechanics**

A crane is configured as below, with the beam suspended at two points l1 and l2 by each end of a cable passing over a frictionless pulley. The two ends of the cable each make an angle θ with the beam. A counterbalance object C with mass mC is fixed at one end of the beam...
*November 26, 2013*

**Math**

Solve for B: A=1/2(b+B) h show work. I am struggling with the above equation can someone please help? Thanks
*November 10, 2013*

**Physics Classical Mechanics**

A rod is lying at rest on a perfectly smooth horizontal surface (no friction). We give rod a short impulse (a hit) perpendicular to the length direction of the rod at X. The mass of the rod is 3 kg, and its length is 50 cm. The impulse is 4 kg⋅m/sec. The distance from ...
*November 7, 2013*

**Physics Classical Mechanics**

A solid disk 1 with radius R1 is spinning freely about a frictionless horizontal axle l at an angular speed ω initially. The axle l is perpendicular to disk 1, and goes through the center S of disk 1. The circumference of disk 1 is pushed against the circumference of ...
*November 7, 2013*

**Physics Classical Mechanics**

A physical pendulum consists of a disc of radius R and mass m fixed at the end of a rod of mass m and length l . (a) Find the period of the pendulum for small angles of oscillation. Express your answer in terms of m, R, l and acceleration due to gravity g as needed (enter m ...
*November 7, 2013*

**Physics Classical Mechanics**

A uniform stick of mass m and length l is suspended horizontally with end B at the edge of a table as shown in the diagram, and the other end A is originally held by hand. The hand at A is suddenly released. At the instant immediately after the release: (a) What is the ...
*November 7, 2013*

**Physics Classical Mechanics**

A yo-yo of mass m rests on the floor (the static friction coefficient with the floor is μ). The inner (shaded) portion of the yo-yo has a radius R1, the two outer disks have radii R2. A string is wrapped around the inner part. Someone pulls on the string at an angle β...
*November 7, 2013*

**Physics Classical Mechanics**

A light inflexible cable is wrapped around a cylinder of mass m1 , radius R , and moment of inertia about the center of mass Ic . The cylinder rotates about its axis without friction. The cable does not slip on the cylinder when set in motion. The free end of the cable is ...
*November 7, 2013*

**Physics Classical Mechanics**

A pulley of mass mp , radius R , and moment of inertia about the center of mass Ic=12mpR2 , is suspended from a ceiling. The pulley rotates about a frictionless axle. An inextensible string of negligible mass is wrapped around the pulley and it does not slip on the pulley. The...
*November 7, 2013*

**Physics Classical Mechanics**

A playground merry-go-round has a radius of R= 2 m and has a moment of inertia Icm= 9×103kg⋅m2 about a vertical axis passing through the center of mass. There is negligible friction about this axis. Two children each of mass m= 30kg are standing on opposite sides ...
*November 7, 2013*

**Physics Classical Mechanics**

A turntable is a uniform disc of mass m and radius R. The turntable is initially spinning clockwise when looked down on from above at a constant frequency f0. The motor is turned off at t=0 and the turntable slows to a stop in time t with constant angular deceleration. (a) ...
*November 7, 2013*

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