# Posts by help

Total # Posts: 1,444

**chemistry**

For all deexcitations that result in the visible spectrum of hydrogen, what is n ?

*November 15, 2010*

**chemistry**

The X-X bond energy in the hypothetical gas, X2 is 153 kJ/mol. a. How much energy, in joules, is required to break the bond in a single X-X molecule? b. What wavelength of electromagnetic radiation would have the energy required to break the X-X bond? c. In what region of the ...

*November 15, 2010*

**chemistry**

The red line in the Helium spectrum is longer than the red line in the hydrogen spectrum. What does that tell us about the distance between n2 and n3 in helium as compared with the distance between n2 and n3 in hydrogen?

*November 15, 2010*

**chemistry**

In the emission spectrum of hydrogen, some lines are in the infra red range. h l Suggest an electron transition (specify n and n) that is in this range and calculate its corresponding wavelength and delta E.

*November 15, 2010*

**algebra**

are you sure? thank you :)

*November 10, 2010*

**bobpursley???**

i did that and i also wrote the answers next to each question and i just want to know if they are right. are they right? please respond

*November 10, 2010*

**science**

what is the difference between a control and a variable

*November 10, 2010*

**science**

thank you :)

*November 10, 2010*

**science**

what is concentration please say it in an easy to understand answer thank you!

*November 10, 2010*

**8th grade**

According to the U.S. Census Bureau in 2009 there were 21,854,374 veterans in the United States. Veterans of the Korean War accounted for 12.4% of that total, while 10.7% were veterans of World War II. What is the positive difference between the numbers of veterans of the ...

*November 9, 2010*

**math**

According to the U.S. Census Bureau in 2009 there were 21,854,374 veterans in the United States. Veterans of the Korean War accounted for 12.4% of that total, while 10.7% were veterans of World War II. What is the positive difference between the numbers of veterans of the ...

*November 8, 2010*

**11th grade physics**

the horizontal range of a projectile is 4 root 3 times of its maximum height. calculate the angle of projection.

*November 8, 2010*

**11th grade physics**

if action and reaction are always equal and opposite, why don't they always cancel each other and leave no force for acceleration of the body?

*November 8, 2010*

**11th grade physics**

find the value of 60 joule per minute on a system which has 10 cm,100gm, and 1 minute as fundamental units.

*November 8, 2010*

**11th grade chemistry**

thank you so much drbob222. u are a genius. could you check out my physics questions too?

*November 8, 2010*

**11th grade chemistry**

a vessel contains 12 gm of methane gas at t degree celcius temp. and 1 atm. pressure. when the temp. is increased by 10 degree celcius at the same volume, the pressure increases by 10%. calculate the volume and initial temp.

*November 8, 2010*

**math**

when is these rational function equal to zero? 6x^2/(x^3+1)^2=0 -2x/(x^2-1)^2=0

*November 7, 2010*

**math**

verify that the function satisfies the hypothesis of the mean value theorem on the given interval. then find all numbers c that satisfy the conclusion of the mean value theorem. f(x) = x/(x+2) , [1,4]

*November 7, 2010*

**calculus**

use the methods of this section to sketch the curve. y=x^3-3a^2x+2a^3, where a is a positive constant. What do the members of this family of curves have in common? How do they differ from each other?

*November 7, 2010*

**Statistics**

Are these statements true or false? 1. The sample mean, the sample proportion and the sample standard deviation are all unbiased estimators of the corresponding population parameters. 2. If the population is normally distributed with known variance then the sample mean may not...

*November 5, 2010*

**math**

what is the best parking space/shortest that would take the from store 1 to store 2 and back to the car?use the following information: -the distance between store 1 to store 2 is 25 yds wide. -driveway between the sidewalk and parking lot is 10 yds this all they give me please...

*November 4, 2010*

**Math**

y = |x − 4| + 8 Find the x-coordinate of the vertex of the graph. And the y-coordinate of the vertex of the graph. Please help me, I'm stuck!

*November 3, 2010*

**HIstory**

Why did congress feel that construction was a confessional task and not a presidential task?

*November 3, 2010*

**spanish**

what am i doing wrong??

*November 1, 2010*

**spanish**

¿Quién va a preparar la ensalada? Mirta y Lidia Your response: mirta y lidia las va a preparar 3.¿Quién va a cocinar la paella? Alberto y su novia Your response: alberto y su novia los va a cocinar. ¿Quién va a limpiar el apartamento ...

*November 1, 2010*

**Halloween**

It's saturday and halloweens tomorrow. But I was wondering is trick or treating sopost be today or tomorrow? I've heard peolple going today and many people say tomorrow. I know sunday is an school night and some people wiill be at church. I have no idea if I should ...

*October 30, 2010*

**CALC HARD...**

Suppose that 430 ft of fencing is used to enclose a corral in the shape of a rectangle with a semicircle whose diameter is a side of the rectangle. (In the figure below, the blue outline represents the fencing.) Find the dimensions of the corral with maximum area. x= y=

*October 29, 2010*

**CALC HARD...**

Suppose that 430 ft of fencing is used to enclose a corral in the shape of a rectangle with a semicircle whose diameter is a side of the rectangle. (In the figure below, the blue outline represents the fencing.) Find the dimensions of the corral with maximum area. x=? y=? i ...

*October 29, 2010*

**CALC HARD...**

i did get that and i got farther than that but then got completely lost

*October 29, 2010*

**CALC HARD...**

Suppose that 430 ft of fencing is used to enclose a corral in the shape of a rectangle with a semicircle whose diameter is a side of the rectangle. (In the figure below, the blue outline represents the fencing.) Find the dimensions of the corral with maximum area. x=? y=? i ...

*October 29, 2010*

**chemistry**

consider the following reactions O+N2->NO+N Ea=315kj/mol Cl+H2->HCl+H Ea=23kj/mol Why is the activation energy for one much lower that the other. The frequency factor is very close in value for the two. Assume they are the same compute the ratio of the reaction constants...

*October 29, 2010*

**cant post a question**

i tried posting a question but it says that i cant have links in my question but i didn't have any? Anyone know hat to do?

*October 28, 2010*

**chem/math**

thanks that helps alot

*October 28, 2010*

**chem/math**

I need to fid the activation energy but i forgot how to solve for Ea 4.58*10^-15=e^(Ea/2537.02) can you show the work thank you

*October 28, 2010*

**Management**

what economic, social , and political forces have made employee traininng even mor eimportant today than in the past?

*October 28, 2010*

**calculus**

find the absolute maximum and minimum values of f on the given interval f(x)= (x^2-4)/(x^2+4), [-4, 4]

*October 28, 2010*

**physics**

Mary and John are on opposite sides of a seesaw. Mary has 3x the mass of John. If Mary is sitting at a distance of .5m from the fulcrum, how far must John site in order to keep it balanced.

*October 27, 2010*

**calculus**

Use a linear approximation (or differentials) to estimate the given number (2.001)^5

*October 27, 2010*

**physics**

A 70kg man stands on a bathroom scale in an elevator. As the elevator starts moving, the scale reads 90kg Is the elevator acceleration up or down, is the elevator moving up or down?

*October 27, 2010*

**phsics can someone check if i did it right**

A block of wood of mass 3kg is on a rough incline of 37degrees. Find the min value of the coefficient of static friction for the block to remain stationary? Fn=3*9.8cos37 Fn=23.4 3*9.8sin37-us(23.5)=0 us=.743

*October 27, 2010*

**phsics**

A block is at rest on an inclined plane whose elevation can be varied. The coefficient of static friction is μs= 0.4, and the coefficient of kinetic friction is μk = 0.16. The angle of elevation θ is increased slowly from the horizontal. At what value of θ ...

*October 24, 2010*

**Stats-BOB PURSLEY Help, do you know this?**

Is there a rule to figure out if this is a true or false statement? A sample size of 900 is not large enough to conclude that the sampling distribution of p is a normal distribution, when the estimate of the population proportion is .995.

*October 24, 2010*

**Physical Science**

Pitch is to make a plane descend or climb. The pilot adjusts the elevators on the tail to make a plane descend or climb. Lowering the elevators caused the airplane's nose to drop, sending the plane into a down. Raising the elevators causes the airplane to climb.

*October 24, 2010*

**chemistry**

Never mind i figured it out:)

*October 24, 2010*

**chemistry**

To what final volume should you dilute 50.5ml of a 4.75 M KI solution so that 27.5ml of the diluted solution contains 3.10g of KI

*October 24, 2010*

**Ap Chemistry**

:) Thanks you so much! :)

*October 24, 2010*

**12th grade**

Okay, sorry....I posted it again correctly :)

*October 24, 2010*

**chemistry**

Its just a general question. I'm trying to get the van't hoff factor and i think you need to know number of ions present. for example how do you know the # ions present in k2s

*October 23, 2010*

**chemistry**

How do you know the number of ions present in a compound.

*October 23, 2010*

**Chemistry**

Calculate the number of molecules in 3.1466x10^1 grams of sulfur dioxide, SO2

*October 22, 2010*

**Chemistry**

Calculate the number of molecules in 3.1466x10^1 grams of sulfur dioxide, SO2

*October 22, 2010*

**Chemistry**

calculate the grams of sodium in 17.606 g of Na2CO3

*October 22, 2010*

**5th grade**

88.8 or if you round 89

*October 14, 2010*

**4th grade**

all but a circle

*October 14, 2010*

**Physics**

A speedboat starts from rest and accelerates at 2.689x10^0 m/s2 for 6.5062x10^0 seconds. After that, the boat then accelerates at 1.7853x10^0 m/s 2 for 3.1299x10^0 seconds. What is the velocity of the boat at the end of this, expressed in 4 significant figures?

*October 13, 2010*

**chemistry**

please

*October 13, 2010*

**chemistry**

please

*October 13, 2010*

**chemistry**

Help please =)

*October 13, 2010*

**math**

math box! 5=15 10=25 15=35 20=45 25=55 what is the rule

*October 13, 2010*

**science**

try chicken wire

*October 13, 2010*

**Physics**

A car travels a total distance of 3.22911x10^2 m to the East in 6.7135x10^1 s. What is the speed of the car, in m/s with 4 significant figures? Note: Your answer is assumed to be reduced to the highest power possible. Your Answer: x10

*October 12, 2010*

**math**

how do yu find the implicit differentiation for this porblem 4cosx*siny=1

*October 11, 2010*

**math**

Find two point on a circle x^2+y^2=1 where the slope of the tangent line is -2 write the equation for the normal lines at these points.

*October 10, 2010*

**math**

For the given function, find all points on an the graph where the tangent line is horizontal or vertical. y= xsqrt(4-x^2) y= sqrt(1-x^2)(4-x^2)

*October 10, 2010*

**chemistry**

225g

*October 1, 2010*

**chemistry**

of KCl

*October 1, 2010*

**chemistry**

A solution was prepared by dissolving 43.0 of in 225 of water. Calculate the mass percent of in the solution.

*October 1, 2010*

**math**

how?

*September 30, 2010*

**math**

wat is the answer for the pattern 1,3,6?

*September 30, 2010*

**physics**

The flywheel of a steam engine runs with a constant angular speed of 164 rev/min. When steam is shut off, the friction of the bearings and the air brings the wheel to rest in 1.6 h. I found the constant angular acceleration as 1.71rev/min^2. They also ask you to find What is ...

*September 28, 2010*

**Biochemistry**

What is the net ionic equation for Phosphate ion + ammonium molybdate in the presence of nitric acid?

*September 27, 2010*

**physics**

A coin with a diameter of 1.9 cm is dropped on edge onto a horizontal surface. The coin starts out with an initial angular speed of 19 rad/s and rolls in a straight line without slipping. The rotation slows with an angular acceleration of magnitude 2.1 rad/s2. What is the ...

*September 27, 2010*

**physics**

The flywheel of a steam engine runs with a constant angular speed of 164 rev/min. When steam is shut off, the friction of the bearings and the air brings the wheel to rest in 1.6 h. I figured out the constant angular acceleration=1.71 rev/min2 but im not sure how to find:What ...

*September 27, 2010*

**phsics**

A coin with a diameter of 1.9 cm is dropped on edge onto a horizontal surface. The coin starts out with an initial angular speed of 19 rad/s and rolls in a straight line without slipping. The rotation slows with an angular acceleration of magnitude 2.1 rad/s2. What is the ...

*September 27, 2010*

**phsics**

thanks that makes sense

*September 27, 2010*

**phsics**

You plan to throw stones by using a sling of length 1.8 m which you whirl over your head. Suppose you wish to throw a stone a distance of 29 m. What must be the centripetal acceleration of the stone just before its release if it is to reach this distance? Assume that the ...

*September 27, 2010*

**physics**

An arrow, starting from rest, leaves the bow with a speed of 16.5 m/s. If the average force exerted on the arrow by the bow were doubled, all else remaining the same, with what speed would the arrow leave the bow?

*September 25, 2010*

**physics**

A bat flying in a cave emits a sound and receives its echo 0.3 s later. How far away is the cave wall? Assume the speed of sound to be 340 m/s. Answer in units of m.

*September 23, 2010*

**chemistry**

What is the conjugate base of the following substances: a. (CH3)3NH /(CH3)3N b. H3N-CH2-COOH / H3N-CH2-COO c. H3N-CH2-COO / H2N-CH2-COO d. OOC-CH2-COOH / OOC-CH2-COO e. OOC-CH2-COOH / HOOC-CH2-COOH

*September 19, 2010*

**Algebra**

kewl

*September 12, 2010*

**Algebra**

Why is it necessary for the encoding function to be one-to-one?

*September 12, 2010*

**mathematics**

1/3 + 1/6 = simplify it later i need explanation of how you get this for example 3/4 + 1/8 = 3/4=6/8 6/8 + 1/8= 7/8 how did they get 6/8 im confused thanks for helping and please.

*September 12, 2010*

**Algebra**

A size 36 shoe in France is size 3.5 in England. A function that converts shoe sizes in France to those in England is g(x)= 3x-94/4. A size 6 shoe in the United States is size 3.5 in England. A function that converts shoe sizes in England to those in the United States is f(x)=...

*September 12, 2010*

**science**

thanks drwls :)

*September 7, 2010*

**science**

This biome extends across Canada and down the Sierra Nevadas and Rocky Mountains. It has large coniferous forests. This biome is the _____. a) desert b) grassland c) tundra d) taiga e) deciduous forest I PICKED D

*September 7, 2010*

**science**

All the following are conservation practices, EXCEPT______? a) reducing consumption b) reducing production of goods using the resource c) recycling d) restoring the environment e) reducing waste I PICKED D

*September 7, 2010*

**science**

When cold air moves below warm air (which rises), we feel _______, depending on how fast the air moves. a) an earthquake or earth tremor b) a drizzle or rainstorm c) a breeze or wind d) a tornado or thunderstorm d

*August 26, 2010*

**algebra**

solve by elimination 3x+4y=2 6x+8y=4 stuck!!

*July 21, 2010*

**math**

Find y '. y = (2x^3 + 6)(2x^7 - 3)?

*July 4, 2010*

**COM 220**

nEED HELP WITH A FULL SENTENCE OUTLINE ON MEDIA VIOLENCE

*May 27, 2010*

**Aleg**

In 1991, the life expectancy of males in a certain company was 68.2 years. In 1997, it was 70.7 years. Let E represent the life expectancy in year t and let t represent the number of years since 1991. 1) The linear function E(t) that fits the date is E(t)=____t+____ Round to ...

*May 26, 2010*

**Math help please!!!**

edit: should be 3p^2q(1+3q-4q^2)

*May 20, 2010*

**Math help please!!!**

Factor completely 3p^2q + 9p^2q^2 - 12p^2q^3 I have done the following: 3p^2q(1+3q-4q^) but then i get stuck..not sure if that's the final answer..

*May 20, 2010*

**economic**

Rational people think at the margin that is one of the principle that I pickplay a major role out so can you provide an example for each about decision making interaction and the working of the economy.Explaine how that influences the marginal benefits and marginal costs ...

*May 14, 2010*

**economic**

which of the 10 principle do you think play a major role in your decision Provide an example for each about decision making interaction and the working of the economy.Explain how that influences the marginal benefits and marginal costs associated with the decision to purchase ...

*May 14, 2010*

**Math**

Use mathematical induction to prove that 5^(n) - 1 is divisible by four for all natural numbers n. Hint: if a number is divisible by 4, then it has a factor of 4. also, -1 = -5 +4 This is a take home test so I don't want the answer because I want to know how to do it. this...

*May 12, 2010*

**math**

1)In the figure, the vertices of right-angled isosceles triangle ABC are A, B(2,0) and C(8,0) respectively. find the equations of AB and AC 2)If the x-intercept and y-intercept of the straight line L: B(y-2) =Ax+8 are -8 and 3 respectively, find a)the value of A and B b)the ...

*May 11, 2010*

**math: not sure how to figure out**

Suppose a coin is biased so that it has the probilities below for landing on heads or tails on a single toss of the coin. P(h)=0.5020 P(t)=0.4980 If this coin is tossed twice find the probability P(hh)

*May 6, 2010*