# Posts by Sarah

Total # Posts: 5,821

**differential equations**

Nevermind, I got the answer.

**differential equations**

Convert x''+ sin(x) = 0 into a first order system of equations. (x'' refers to the second derivative of x). I tried: y1 = sin(x) y2 = x' {y1' = cosx {y2' = -sinx Not sure if I did it right.

**Algebra**

If you know all the answers please help me. I need help!

**Algebra**

1. determine whether the equation represents a direct variation , if it does find the constant of the vartion 2y=5x+1

**Phyics**

The foci of the elliptical path for an Earth satellite are __________. A) one at Earth's center and the other elsewhere B) one atop the other at Earth's center C) both inside Earth D) both outside Earth

**geometry**

given: -n+6=8n+6n prove:n=0

**Chemistry**

ok I set up the first one right, and got P=.998 atm The after composition makes sense and I got P = 20.0 atm Are these correct?

**Chemistry**

Calculate the pressure of 4.80g of ozone, O3, in a 2.45 L flask at 25 degrees C. Assume that the ozone completely decomposes to the molecular oxygen. 2O3(g) --> 3O2(g) Calculate the pressure inside the flask once the reaction is complete.

**Chemistry (Check)**

correct

**Chemistry (Check)**

What is the volume of the gas in a balloon at -195 degrees C if the balloon has been filled to a volume of 5.0L at 25 degrees C? Vf = 1.3L

**Chemistry**

Is it just .8252 kg/cm^3? because multiply 1000cm^3 / 1000kg

**Chemistry**

Calculate the density of methane gas, CH4, in kilograms per cubic meter at 25 degrees C and 956 mmHg. I got .8252 g/L but am getting confused with the converting units.

**Chemistry**

Calculate the pressure in an evacuated 250mL container at 0 degrees C when the O2 in 1.00 cm^3 of liquid oxygen evaporates. Liquid oxygen has a density of 1.118 g/cm^3.

**Science**

Nonmetals are often brittle

**Biology**

to produce a substance

**Business**

My apologies. It is the Harvard Business Review, not the Harvard Business Journal.

**Business**

I have to write a two page paper about a journal article. The article is "Beware the Next Big Thing" published in the Harvard Business Journal, 2014. In the essay I have to include: a. methodology b. objectives c. summary of research results d. managerial ...

**Math**

11

**Math**

It is not a function because there are multiple y-values paired with a single x-value

**physics**

A cross-country skier who weighs 600 N has chosen ski wax that provides ฯ=0.03. What is the minimum amount of horizontal force,perhaps from a tailwind,that would keep the skier coasting at constant speed across level snow?

**math**

The track team plans to sprint 20 miles this school year. The runners will sprint 1/4 mile each day.How many days will it take them to sprint 20 miles?

**Chemistry (Edit)**

The CH3 in a is supposed to be under the second C in the compound.

**Chemistry**

Isomers are compounds that have the same number and kinds of atoms but have a different arrangement of the atoms. The enthalpies of atom combination for several pairs of gaseos isomers are given here. For each pair, decide which has the strongest bonds. a. CH3CH2CH2OH -4391....

**math help one question**

Standard form

**Math**

Standard form

**Chemistry**

Nitrogen and oxygen can react directly with one anotheer to produce nitrogen dioxide according to N2(g) + 2O2(g) --> 2NO2(g) The reaction may also be imagined to take place by first producing nitrogen oxide N2(g) + O2(g) --> 2NO(g) which then produces NO2 2NO(g) + O2(g...

**Math**

31,250 with prime factorization = 2x5^6

**Chemistry**

Oxyacetylene torches are fueled by the combustion of acetylene, C2H2. 2C2H2(g) + 5O2(g) --> 4 CO2(g) + 2H2O(g) If the enthalpy change for the reaction is -2511.14 kJ/molrxn, how much heat can be produced by the reaction of a. 2mol of C2H2? b. 1 mol of C2H2? c. .500 mol of ...

**Social Studies (please help)**

It is around the 500 to 600 CE

**Social Studies (please help)**

In what ways were diverse people from the Arabian Peninsula through the Middle East, North Africa, and into Spain united? What held them together and unified them, and how was this done?

**Chemistry**

Why are the two words "alkaline" and "earth" used to name the group 2 metals?

**Chemistry**

Which of the following nitrogen-containing compounds would supply the most nitrogen per gram of fertilizer? a. iron azide, Fe(N3)2, MW = 140 g/mol b. sodium azide, NaN3, MW = 65 g/mol c. potassium nitrite, KNO2, MW = 85.1 g/mol d. potassium azide, KN3, MW = 81.1 g/mol e. There...

**Physics**

2. Consider the ball example in the introduction when a ball is dropped from 3 meters. After the ball bounces, it raises to a height of 2 meters. The mass of the ball is 0.5 kg a. What is the speed of the ball right before the bounce? b. How much energy was converted into heat...

**Chemistry**

Describe how you would prepare 500 mL of a 0.10 M solution of HCl from a 12.0 M solution of HCl.

**Chemistry.**

Mg+2HCl--->MgCl2+H2 Using the balanced equation, how many moles of H2 will you make if you start with .00082 moles of Mg solid? How many grams of H2 is that?

**Science**

252g

**civics**

HELP ME PLEAASSEEE!!!!!!!

**civics**

What motivated the Founding fathers to include the phrase "to form a more perfect union" in the preamble of the U.S Constitution?

**civics**

I think its B

**Physics**

A curling stone with a mass of 18 kg slides 38m across a sheet of ice in 8.0 s before it stops because of friction. What is the co¨efficient of kinetic friction between the ice and the stone? (Note: you will need to calculate the acceleration of the stone first.) I solved ...

**Physics**

An object initially at rest experiences an acceleration of 9.8 m/s^2. How much time will it take to achieve a velocity of 58 m/s?

**Chemistry! HELP**

A chemistry student used the symbol "sx" to represent an s orbital that lies along the x-axis. Is this reasonable. Justify your answer.

**Chemistry! HELP**

What information about an electron in an atom is given by the following quantum numbers? 2px+1/2 Answer? (idk if this is right) : An electron located in the p orbital in the 2nd main enrgy level would be said to be located in the 2p sublevel.

**physics**

A 214-kg crate rests on a surface that is inclined above the horizontal at an angle of 19.4°. A horizontal force (magnitude = 541 N and parallel to the ground, not the incline) is required to start the crate moving down the incline. What is the coefficient of static ...

**Reading**

Did you find the answer to the question yet?

**Science**

If you guys are still looking for answers if you go to part on of the question there is a link that you use to find the answer.I hope this helped :)

**Science**

FYI I am not plagiarizing because all the credit is given to the people who made it |-/

**Science**

If you guys are still looking for answers if you go to part 1 of the question there is a link that you use to find the answer.I hope this helped :) Because collisions between large planetesimals release a lot of heat, the Earth and other planets would have been molten. (Brian ...

**Math**

Look at the orange mama laid

**Pre-calculus**

Thanks, Ms.Sue! You are amazing!

**Pre-calculus**

I have (x,y,z)=(-5a-15,-a-5,a)

**Pre-calculus**

Solve the system of linear equations and check any solutions algebraically. (If there is no solution, enter NO SOLUTION. If the system is dependent, express x, y, and z in terms of the parameter a.) x-3y+2z=21 5x-13y+12z=81 I have an answer but i'm not sure if it's ...

**physics**

The drawing shows four point charges. The value of q is 1.4 μC, and the distance d is 0.86 m. Find the total potential at the location P. Assume that the potential of a point charge is zero at infinity

**English**

I'm just looking for some ideas for an essay on a Tale of Two Cities.... it can be anything related to the book... and I'm not asking you to do my schoolwork for me... I can develop the thesis and points but I just need some ideas... this is for a 4u course and I ...

**Chemistry**

doesnt the concentration come into play some how?

**Chemistry**

When 22.3 mL of 1.00 M AgNO3 is mixed with 21.7 mL of 1.50 M NaCl, the temperature of the mixture rises for 21.6 degrees C to 29.7 degrees C. The mass of the aqueous mixture is 45.9 grams and its specific heat capacity is 3.94 J/grams degrees C. I calculated (45.9g)x (3.94J/g ...

**College Algebra**

A train leaves New York for Boston, 200 miles away, at 3:00 P.M. and averages 70 mph. Another train leaves Boston for New York on an adjacent set of tracks at 4:00 P.M. and averages 55 mph. At what time will the trains meet? (Round to the nearest minute.)

**Science**

A hypothetical element has two main isotopes with mass numbers of 56 and 59. If 61.00% of the isotopes have a mass number of 56 amu, what atomic weight should be listed on the periodic table for this element?

**functions and trig**

write the transformation of X cubed if it is shifted right four units and then reflected over the X axis

**Pre-calculus**

STEVE YOU THE MAN! THANK YOU!

**Pre-calculus**

Complete the table assuming continuously compounded interest. (Round your answers to two decimal places.) Initial Investment: Annual % Rate: Time to Double: 8 yr Amount After 10 Years: $1700 I don't understand how to get in the initial investment of annual % rate given ...

**Algebra**

Determine a polynomial function of degree 3 with real coefficients whose zeros are ƒ{2, 1+i .

**Chemistry**

yes I need to find delta H. I calculated (45.9g)x (3.94J/g Celsius) x (8.1 Celsius), which came out to 1464.8526 Joules. How do I use this into solving for Delta H?

**Chemistry**

When 22.3 mL of 1.00 M AgNO3 is mixed with 21.7 mL of 1.50 M NaCl, the temperature of the mixture rises for 21.6 degrees C to 29.7 degrees C. The mass of the aqueous mixture is 45.9 grams and its specific heat capacity is 3.94 J/grams degrees C

**Biology**

In phylogenetics, we use the terms monophyletic, polyphyletic, and paraphyletic. What do each of these terms mean? How might the concept of shared, derived traits fit with these terms? I know what each of the terms mean. I am not sure about the second question.

**science**

Cutie was 100% correct. Thank you:)

**Biology**

What are the three conditions that must be met for natural selection to occur? What should happen if those three conditions are met? Define each type of natural selection, and describe what you expect to happen over time if these types of natural selection occur. Do these ...

**Biology**

Why is the Hardy-Weinberg Theorem useful for studying evolutionary change? What are the assumptions of this model? How does it work (in other words, describe the procedure which is used and how you figure out genotype frequencies)?

**Science**

I think 7 is b

**Science**

I need help with this too :/

**Algebra**

A 52 in. board is cut into two pieces. One piece is three times the length of the other. Find the length of the other piece.

**Physics**

A ball of mass 0.6 kg, initially at rest, is kicked directly toward a fence from a point 20 m away. The velocity of the ball as it leaves the kicker's foot is 17 m/s at angle of 45 degrees above the horizontal. The top of the fence is 6m high. The ball hits nothing while ...

**Chemistry**

I figured out I went wrong when calculating the moles of hydrogen. I used the molar mass of just one hydrogen since I was calculating the moles of one mole of hydrogen. I didn't know that I had to 2X the g/mol of hydrogen. Is there an explanation why this is?

**Chemistry**

Oh sorry, the question also gives this information:the 0.2041g of H2O were also produced.

**Chemistry**

A 0.1592g sample of a hydrocarbon upon combustion analysis produces 0.5008g CO2. Its molar mass is found in another experiment to be 70g mol. Determine the empirical formula, and its molecular formula. I completely messed up this question, and I don't know where I wen'...

**World History**

Thanks Reed :)

**World History**

I have to write a paper about the the similarities and differences of Ancient China and Persia. Anyone know any good websites I could use for research?

**Algebra**

A luxury car rental company charges $150 per day in addition to a flat fee of $50 for insurance. Write an equation that represents the cost, f(x), (in dollars) to rent the car for x days. This equation should be in slope-intercept form.

**algebra**

solve the system using elimination 2x-5y=8 x-3y=-1 please explian step by step

**Chemistry**

4.760 g of a substance (containing only C, H, and O) is burned in a combustion analysis apparatus. The mass of CO2 produced is 1.276×101 g, and the mass of H2O produced is 3.134 g. What is the empirical formula of the compound? I keep getting CH5O2, which is incorrect!

**Calculus**

Let u=f(r) and r=|x|=((x1)^2 +···|(xn)^2)^1/2. Show that ∑ (∂u/∂xj)^2 = (f′(r))^2 Please help! it's an assignment due tomorrow

**Chemistry**

Q: 26.30mL of 0.1105 mol/L H3PO4 solution is neutralized by 139.50 mL of KOH. Calculate the mass of solid KOH required to prepare 500.0 mL of this solution. In the previous part of this question, it asked the concentration of KOH and I worked it out to be concentration of KOH ...

**Physics**

An incline is divided into 6 equal lengths. Starting from rest a ball accelerates down the incline. It takes 0.21 seconds to reach the first tape marker, a distance of 0.15 meter.

**Physics**

A student drops a rock from a bridge to the water 12.0 meters below. With what speed does the rock hit the water?

**phyics**

A car takes 11 s to go from v=0m/s to v = 22 m/s at constant acceleration. If you wish to find the distance traveled using the equation d=1/2at2, what value should you use for a? Express your answer to two significant figures and include the appropriate units. please help me ...

**phyics**

A dart leaves the barrel of a blowgun at a speed v. The length of the blowgun barrel is L. Assume that the acceleration of the dart in the barrel is uniform. a) Show that the dart moves inside the barrel for a time of 2L/v Express your answer in terms of the variables L and v...

**Physics**

Two hikers are climbing up a mountain and one throws a first aid kit up to another at an initial velocity of 11 m/s and at an angle of 62 deg above the horizontal. At the moment it is caught, the vertical speed is zero. What is the difference in height between the two climbers...

**math**

So take 1 2/5 and convert it into an improper fraction. Then multiply your improper fraction by 1/5 to see how much the second garden will need. Finally add the two numbers together

**History**

Imagine that you are Thomas Jefferson. You receive a letter from someone living in the colonies who does not understand what natural rights are, or how the King of England has violated them. Help please and thank you!

**History**

Life, Liberty and Pursit of happiness?!?

**History**

Yeah. But how would I put this in a sentence?

**History**

According to the Declaration of Independence, what are the three natural rights that are guaranteed to people? Can you help me with this question?

**History**

To be honset. I don't understand what those mean

**History**

Life, Liberty and the pursuit of Happiness.

**History**

Natural rights are rights that cannot be taken away by a government.

**History**

Examples of natural rights in declaration of independence! Please Help

**math,**

A jeweler is heating a gold bar. It takes 7 joules of heat to raise the temperature of the bar 1°C. The initial temperature of the bar is 25°C. Use this information for Items 4–11. 4. Make a table that shows how many joules of heat would be required to raise the ...

**Grammar**

Is this correct grammar? Sarah has 6 oranges. Ted has 7 oranges. How many oranges do they have altogether?

**math**

A jeweler is heating a gold bar. It takes 7 joules of heat to raise the temperature of the bar 1°C. The initial temperature of the bar is 25°C. Use this information for Items 4–11. 4. Make a table that shows how many joules of heat would be required to raise the ...

**algebra**

A jeweler is heating a gold bar. It takes 7 joules of heat to raise the temperature of the bar 1°C. The initial temperature of the bar is 25°C. Use this information for Items 4–11. 4. Make a table that shows how many joules of heat would be required to raise the ...