Monday
December 22, 2014

Posts by Sarah


Total # Posts: 4,458

Chemistry
Dimethylamine burns in oxygen according to the following equation: 4 C2H7N + 15 O2 → 8 CO2 + 14 H2O + 2 N2 (a) How many liters of O2 at 35 °C and 0.840 atm will be needed to burn 7.70 L of C2H7N at 35 °C and 0.840 atm? (b) How many liters of CO2 at 35 °C and ...
December 1, 2012

Chemistry
= 728/(2.807)(0.08206)(291.15) =10.855 g ?
December 1, 2012

Chemistry
What is the molar mass of a compound if a gaseous sample has a density of 2.807 g/L at 18 °C and 728 torr?
December 1, 2012

Physics !:(
A carbon dioxide laser is an infrared laser. A CO laser with a cavity length of 48.6cm oscillates in the m=100,000.0 mode. What is the wavelength of the laser beam? b). What is the frequency of the laser beam?
November 30, 2012

Calculus
Find the derivative of y = x^x
November 28, 2012

Calculus
Find the maximum volume of a cylindrical tin that has a total surface area of 600pi cm^2.
November 28, 2012

Math
I need help figuring out the unit rate for $5/3. Please help, :D
November 28, 2012

science
In cattle, red hair and white hair are codominant. Cattle with both white hair and red hair are what? please help! thanks!
November 27, 2012

Physics
1.6
November 27, 2012

Physics
A toy is attached to the cieling by a string. As the toy flies around in a horizontal circle with a radius 45 cm, the string makes an angle of 60 degrees with the cieling. What is the speed of the toy?
November 27, 2012

physics
Suppose the roller coaster in Fig. 6-41 (h1 = 34 m, h2 = 10 m, h3 = 30) passes point 1 with a speed of 1.60 m/s. If the average force of friction is equal to one fourth of its weight, with what speed will it reach point 2? The distance traveled is 60.0 m.
November 26, 2012

math 3rd grade
How can you use 4x7 to find 8x7? find the product. I dont understand this how can i expect my 3rd grader to understand.
November 26, 2012

Physics HELP!!
a). The displacement of a wave travelling in the positive x-direction is D(x,t)=(5.94cm)sin(1.18x-132.6t), where x is in meters and t is in seconds. What is the frequency? b). What is its wavelength? c).What is the speed of the wave?
November 24, 2012

physics ..PLEASE HELP ASSIGN DUE SOON :(
A jet airplane has an intensity of 97.7W/ m^2 when heard at a distance of 30.0m. What is the maximum sound intensity heard by a person on the ground when the airplane is 10100m overhead?
November 24, 2012

physics ..PLEASE HELP ASSIGN DUE SOON :(
A microphone has an area of 3.0cm^2. It receives during a 6.00s time period a sound energy of 1.0x10-11J. What is the intensity of the sound? b). Using the intensity in the previous question, what is the variation of pressure in the sound wave if the speed of sound is 343m/s ...
November 24, 2012

Spanish
whenever the word 'que' is used in a sentence and a verb follows it, the verb will always be in the unconjugated form. Tenemos que IR al parque. tienen que ESTUDIAR. tengo que HACER mi tarea.
November 21, 2012

Physics
For a certain transverse wave, the distance between two successive crests is 4.48m, and 13 crests pass a given point along the direction of travel every 5.97s. Calculate the wave speed!
November 21, 2012

Physics HELP!!
Earthquakes are essentially sound waves travelling through the earth. They are called seismic waves. Because the earth is solid, it can support both longitudinal and transverse sismic waves, which travel at different speeds. The speed of longitudinal waves, called P waves, is ...
November 21, 2012

Physical
It is experiment electric resistivty For the pencil line
November 20, 2012

Physical
The pencil line is made out of carbon atoms. Assuming that the average diameter of a carbon atom is 3.49x10^-10m, how many atoms thick is the pencil?
November 20, 2012

Physics
Football is kicked up into the air with a velocity of 20m/s. a. Determine the time the football is in the air. b. Determine the maximum height the football would reach. c. As the ball is kicked it encounters a weird horizontal wind that gives it a velocity of 5m/s. Determine ...
November 19, 2012

Physics
part 1 of 3: A hawk flies in a horizontal arc of radius 9.9 m at a constant speed of 4.8 m/s. Find its centripetal acceleration. Answer in units of m/s^2. part 2 of 3: It continues to fly along the same horizontal arc but increases its speed at the rate of 1 m/s^2. Find the ...
November 19, 2012

Physics URGENT!!!
A spring of negligible mass stretches 2.14 cm from its relaxed length when a force of 8.40 N is applied. A 1.300 kg particle rests on a frictionless horizontal surface and is attached to the free end of the spring. The particle is displaced from the origin to x=5.00 cm and ...
November 19, 2012

algebra
Find the cost of a home in 20 years, assuming an annual inflation rate of 5%, if the present value of the house is $260,000.
November 18, 2012

chemistry... HELP !!!!!!!
The average bond enthalpy for C__H is 413 kJ/mol. In other words, 413 kJ of energy is required to break a mole of CH into atoms: CH (g) ----> C(g) + H(g) delta H= 413 kJ Using this information, and enthalpy of C6H6=5535kJ, calculate the enthalpy change of the reaction: C6H6...
November 18, 2012

CHEMISTRY
Consider a 58.4 g sample of H2O(g) at 125°C. What phase or phases are present when -162 kJ of energy is removed from this sample? Specific heat capacities: ice, 2.1 J g-1 °C-1; liquid, 4.2 J g-1 °C-1; steam, 2.0 J g-1 °C-1, ΔHvap = 40.7 kJ/mol, ΔHfus...
November 17, 2012

CALCULUS
Find the length of the curve: y=ln(1-x^2), 0<_x<_1/2
November 16, 2012

CALCULUS
Let R be the region bounded by y=e^x, y=2. and the y-axis. Find the volume of the solid obtained by rotating the y-axis.
November 15, 2012

trig
given that 1/2pi<theta<pi and sin theta=1/5, use appropriate trigonometric formulas to find the exact values of the following (i) cos(2theta) (ii) cos theta (iii) sin(2theta)
November 15, 2012

PHYSICS
At what temperature would the rms speed of a nitrogen atom equal the following speeds? (Note: The mass of a nitrogen atom is 2.324 10-26 kg.) (a) the escape speed from Earth, 1.12 104 m/s _____K (b) the escape speed from the Moon, 2.37 103 m/s _____K
November 14, 2012

PHYSICS
An air bubble has a volume of 1.65 cm3 when it is released by a submarine 105 m below the surface of a lake. What is the volume of the bubble when it reaches the surface? Assume the temperature and the number of air molecules in the bubble remain constant during its ascent. ...
November 14, 2012

PHYSICS
One mole of oxygen gas is at a pressure of 5.25 atm and a temperature of 29.5°C. (a) If the gas is heated at constant volume until the pressure triples, what is the final temperature? ____°C (b) If the gas is heated so that both the pressure and volume are doubled, ...
November 14, 2012

PHYSICS
The average coefficient of volume expansion for carbon tetrachloride is 5.81 10-4 (°C)−1. If a 42.5-gal steel container is filled completely with carbon tetrachloride when the temperature is 10°C, how much will spill over when the temperature rises to 26.5°C...
November 14, 2012

PHYSICS
The Trans-Alaskan pipeline is 1300 km long, reaching from Prudhoe Bay to the port of Valdez, and is subject to temperatures ranging from -72°C to +38°C. (a) How much does the steel pipeline expand due to the difference in temperature? (The coefficient of linear ...
November 14, 2012

PHYSICS
Lead has a density of 1.13 104 kg/m3 at 0°C. (a) What is the density of lead at 86°C? ___kg/m3 (b) Based on your answer to part (a), now consider a situation in which you plan to invest in a gold bar. Would you be better off buying it on a warm day? Yes or No Explain.
November 14, 2012

Chemistry
What is the wavelength in Angstroms of radiation that has a frequency of 4.00 x 10^14 s-1? I tried the equation wavelength= constant / frequency. And the fact that 1 Angstrom = 1x 10^-10 m, but I don't see how the correct answer turns out to be 7.5 x 10^3
November 14, 2012

Chemistry
What is the energy in Joules of a mole of photons of microwave light having a frequency typical of microwave? (frequency = 3.0 x 10^9 Hz) I tried using the equation E= h x frequency, but I ended up with the answer 1.98 x 10^-24 instead of the correct answer 1.2 J, so there ...
November 14, 2012

Chemistry
What is the total volume of gases produced at 819 K and 1. atm pressure when 320 g of ammonium nitrite undergoes the following decomposition reaction? NH4NO2 --------> N2(g) + 2H2O(g)
November 14, 2012

Chemistry
Thanks so much, I would of never figured out that out myself past the empirical formula since I forgot about the 22.4L factor. The molar mass turns out to be 70, and since the only answer I was given that adds up to 70 is C5H10, it's an easy pick. Pentane!
November 14, 2012

Chemistry
An unknown gaseous hydrocarbon consists of 85.63% carbon by mass. A 0.335 g sample of the gas occupies a volume of 0.107 L at STP. What is the identity of the gas?
November 14, 2012

Chemistry
A 3.80 L cylinder contains 6.83g of methane, CH4, at a pressure of 3320 mmHg. What is the temperature of the gas? I know you use the formula PV= nRT, but I can't seem to get two sides equal each other, thus having the wrong temp. My guess is that I have to change mmHg to a...
November 14, 2012

Physics HELP!!
Four masses are connected by 27.1cm long, massless, rigid rods. If massA=237.0g, massB=511.0g, massC=257.0g, and massD=517.0g, what are the coordinates of the center of mass if the origin is located at mass A? ^ I already got this part: x coordinate- 13.78 cm y coordinate- 13....
November 13, 2012

Physics
A street lamp weighs 160 N. It is supportedequally by two wires that form an angle of 119 with each other. What is the tension of each of these wires? Answer in units of N
November 12, 2012

Chemistry
A 3.80 L cylinder contains 6.83 g of methane, CH4, at a pressure of 3320 mmHg. What is the temp. Of the gas? I mainly have problems being able to tell which gas law equation I need to use when asked these types of questions and then being able to rearrange the equation to find...
November 12, 2012

Physics
A hiker who weighs 834N, is strolling through the woods and crosses a small horizontal bridge. The bridge is uniform, weighs 3520N, and rests on two concrete supports at each end. He stops one-fifth of the way along the bridge. What is the magnitude of the force that a ...
November 12, 2012

Physics HELP!! pleasee
A uniform plank of length 5.0 m and weight 231N rests horizontally on two supports, with d = 1.34m of the plank hanging over the right support. To what distance, x, can a person who weighs 477N walk on the overhanging part of the plank before it just begins to tip?
November 12, 2012

Physics B
Part 1 A 36 kg girl is standing on a 65 kg plank. The plank, originally at rest, is free to slide on a frozen lake, which is a flat, frictionless supporting surface. The girl begins to walk along the plank at a constant speed of 1.89 m/s to the right relative to the ...
November 12, 2012

Algebra
2x+3=-2x+5 I think the answer is 8 ______________________________ 1-2x-5=4x+2 2x=8? X=4? I doubt I got this right
November 12, 2012

Algebra
3x + 7= -x - 1 -3x=x-(6-2x) 1-2x-5=4x+2 2x+3=-2x+5 I cant remember the steps to evaluate.
November 12, 2012

Its math, cmon answer!!!
Andrew guess what, I was a tid bit busy. So spare the tude. thanks Bobpursley.
November 11, 2012

Its math, cmon answer!!!
This is my HW problem; I'm thinking of a number. When I double my number, subtract five, and then add my original number, I get one. What's my number?
November 11, 2012

physics
A cook holds a 2.66-kg carton of milk at arm's length (see the figure below). What force B must be exerted by the biceps muscle? (Ignore the weight of the forearm. State the magnitude of the force B.)
November 11, 2012

physics
Suppose a 34.5-kg child sits 1.17 m to the left of center on the same seesaw as the problem you just solved in the PRACTICE IT section. A second child sits at the end on the opposite side, and the system is balanced.
November 9, 2012

physics
k(.005m)=((8.99X10^9)*(2.70X10^-6)*(8.60X10^-6))/(.09m)^2 k=5.15X10^3
November 7, 2012

economics
1. When the government attempts to cover large deficits by creating more money, what is the probable result called? (1 point) (0 pts) government borrowing (1 pt) hyperinflation (0 pts) excess currency (0 pts) full employment 1 /1 point 2. What is one of the major problems ...
November 6, 2012

caluculating the interest! please help
Calculate the interest on a $1700 credit card bill that shows a 22% APR, using the average daily balance method. Assume you sent a payment of $375 on the first day of a month that has 30 days and it takes 5 days for this payment to be received and recorded. Round to the ...
November 6, 2012

MATH
you mean 1700x0.02x1/12=31.16? that is not the right answer though :(
November 6, 2012

MATH
Calculate the interest on a $1700 credit card bill that shows a 22% APR, using the average daily balance method. Assume you sent a payment of $375 on the first day of a month that has 30 days and it takes 5 days for this payment to be received and recorded. Round to the ...
November 6, 2012

Physics- PLEASE HELP
A 10.0 kg cylinder rolls without slipping on a rough surface. At an instant when its center of gravity has a speed of 16.0 m/s, determine (a) the translational kinetic energy of its center of gravity.(b) the rotational kinetic energy about its center of gravity, and (c) its ...
November 6, 2012

chemistry
Given the reaction: H2SO4 = 2NaOH -> NaSO4 = 2H20. Determine the # of moles of sulfuric acid id needed to completely react with 2.3 L of 0.5 M of NaOH. Then determine the concentration of the solution if 3.0 L of it are used instead.
November 4, 2012

chemistry
Given the reaction: H2SO4 = 2NaOH -> NaSO4 = 2H20. Determine the # of moles of sulfuric acid id needed to completely react with 2.3 L of 0.5 M of NaOH. Then determine the concentration of the solution if 3.0 L of it are used instead.
November 4, 2012

Physics
A crane lifts the 22000kg steel hull of a ship out of the water. Determine the tension in the crane's cable when the hull is submerged in the water. Determine the tension when the hull is completely out of the water.
November 3, 2012

Physics
A 19cm radius air duct is used to replenish the air of a room 9.2m x 6.0m x 4.0m every 18min . How fast does air flow in the duct?
November 3, 2012

Physics
What is the total force on the bottom of a swimming pool 27.5m by 9.0m whose uniform depth is 1.9m? physics What is the absolute pressure on the bottom of a swimming pool? What will be the pressure against the side of the pool near the bottom?
November 3, 2012

physics
a drunken motorist who is moving at a constant velocity of 90 km/h passes a stationary police patrol car. The patrol car immediately gives chase at a constant acceleration and catches up with the motorist after a distance of 10 km. Calculate the time taken by the patrol car to...
November 2, 2012

Physics
A car is stopped at a stoplight. When the light turns green, it accelerates with a constant acceleration of 2.5 m/s^2. At the same instant, a truck passes the car in the same direction with a constant velocity of 15 m/s. how long until the car catches the truck?
November 1, 2012

math
how many possible combinations are there to make $1.55 using a dollar, dimes and pennies?
November 1, 2012

math
how do i find the equivalent decimal for 2 3/4
November 1, 2012

PHYSICS HELP-multiple choice
A red ball with a velocity of +3.0 m/s collides head-on with a yellow ball of equal mass moving with a velocity of -2.0 m/s. What is the velocity of the red ball after the collision? A. zero. B. -2.0 m/s. C. +3.0 m/s. D. +2.5 m/s. E. +5.0 m/s. I think zero but need a second ...
October 31, 2012

Physics
A(n) 95.7 kg boxer has his first match in the Canal Zone with gravitational acceler- ation 9.782 m/s2 and his second match at the North Pole with gravitational accelera- tion 9.832 m/s2. a) What is his mass in the Canal Zone? Answer in units of kg b) What is his weight in the ...
October 30, 2012

Physics
A(n) 95.7 kg boxer has his first match in the Canal Zone with gravitational acceler-ation 9.782 m/s2 and his second match at the North Pole with gravitational accelera- tion 9.832 m/s2.
October 30, 2012

Computer Science
public class RandomPhoneNumber { public static void main(String[] args) { int num1=(int)(Math.random()*7); int num2=(int)(Math.random()*7); int num3=(int)(Math.random()*7); int set1=(int)(100+Math.random()*642); int set2=(int)(1000+Math.random()*8000); System.out.println("...
October 30, 2012

Physics- Elena please help!
Assume you are agile enough to run across a horizontal surface at 11.60 m/s on an airless spherical asteroid of uniform density 1.0x103 kg/m3, independently of the value of the gravitational field. To launch yourself into orbit by running, what would be (a) the radius? (b) the...
October 29, 2012

Chemistry
a silver coin has a mass of 2.50g and is analysed for silver by dissolving in dilute nitric acid, and precipitating silver as solid AgCl and weighing this. if the percipitat weighs 2.99g what percentage of silver is the coin?
October 29, 2012

Geometry
Which statement about a figure ABCD would always be true ?
October 28, 2012

Organic Chemistry
I think I got something: there should be 2 Rf values, since there are two components; maybe the spot was not concentrated enough. So the way to fix the error would be to make the spot bigger. Is this right?
October 28, 2012

Organic Chemistry
Identify the error in the following scenario and indicate how you would fix the error: A TLC of a two component mixture of pentene and 1,3-diethylbenzene was run in acetone. An Rf value of 0.90 was reported.
October 28, 2012

CHEMISTRY
Calculate the change in entropy that occurs when 17.68 g of ice at -12.7°C is placed in 54.05 g of water at 100.0°C in a perfectly insulated vessel. Assume that the molar heat capacities for H2O(s) and H2O(l) are 37.5 J K-1 mol-1 and 75.3 J K-1 mol-1, respectively, and...
October 23, 2012

math
A right triangle is formed in the first quadrant by the x- and y-axes and a line through the point (2,3). Draw a figure that illustrates the problem. What is the area of the triangle A as a function of the x-intercept of the line?
October 22, 2012

Physics help PLZ!!
Estimate the energy required from fuel to launch a 1465 kg satellite into orbit 1375 km above the Earth’s surface. Consider two cases: (a) the satellite is launched into an equatorial orbit from a point on the Earth’s equator, and (b) it is launched from the North ...
October 22, 2012

Algebra
thank you so much!!! 😄
October 20, 2012

Algebra
2-(3x-4)=2x-9 X=? help would be lovely 😊
October 20, 2012

arithmetic
$30.00 x .6/2-$17.50=
October 18, 2012

Force Physics
I don't know how to find the answer to the bottom scale yet; but I found the top scale by adding both the masses. Then times that number by 10, which is g.
October 18, 2012

science
The block of mass 4.44723 kg has an acceleration of 4.6 m/s^2 4.44723 kg F is at 30◦ a What is the magnitude of F? Assume the acceleration due to gravity is 9.8 m/s 2 and the surface is frictionless. Answer in units of N
October 17, 2012

science
A 14700 kg sailboat experiences an eastward force of 29800 N due to tide pushing its hull while the wind pushes the sails with a force of 81500 N directed toward the northwest (45◦ westward of North or 45◦ northward of West). What is the magnitude of the resultant ...
October 17, 2012

Math
oh, okay. now I get it. thanks!!!
October 16, 2012

Math
this is confusing :( this is how I am solving. 66 2/3 12 ------- = ----- 100 W so i mulitiplyed 100x12= 2100. and from here I don't know how to insert 66 2/3 into calculator. 2100 divided by 66.667? the choice to answers are 14, 3.17, 315 and 31.5 I know for sure that 14 ...
October 16, 2012

Math
21 is (66 and 2/3)% of what number? I believe the answer is 14. is it right?
October 16, 2012

statistics
A group of 200 students takes the Kaplan course in hopes that it will improve their SAT scores above the national mean of 500 on the math section. The population standard deviation of the SAT is known to be 100. Use an alpha level of .05 when answering the following questions...
October 16, 2012

Physics
A 50kg object is moving at 25m/sec. How many calories are generated when the object brakes to a stop?
October 16, 2012

Physics
** TWO very small..
October 15, 2012

Physics
wo very small spheres are initially neutral and separated by a distance of 2.73 m. Suppose that 2.60E+13 electrons are removed from one sphere and placed on the other. What is the magnitude of the electrostatic force that acts on each sphere?
October 15, 2012

Physics
Aiyana drives for 100 s at a rate of 20m/s, then turns around and drives for another 200 s at a rate of 30m/s and completes the rest of her journey at a rate of 90m/s for 100 s. what is her average velocity?
October 14, 2012

Spanish
me estoy cepillando los dientes me estoy maquillando me estoy bano me estoy sacando la basura me estoy poniendo me estoy nerviosa
October 14, 2012

c++
Your Mathematic school teacher want to use a program that can read the name and the mark of a student. Your teacher want the program to automatically find the grade of the mark and display the result(name, mark and grade). Help your teacher to develop a program that can solve ...
October 11, 2012

CHEMISTRY
The enthalpy of neutralization for the reaction of a strong acid with a strong base is −56 kJ/mol of water produced. How much energy will be released when 200.5 mL of 0.400 M HCl is mixed with 149.1 mL of 0.500 M NaOH?
October 9, 2012

Chemistry
Integrate the expression β = 1/V (δV / δT) at constant pressure, assuming that β is independent of temperature. By doing so, obtain an expression for V as a function of T and β at constant P.
October 9, 2012

physics
A skier squats low and races down an 11◦ ski slope. During a 3 s interval, the skier accelerates at 2.7 m/s^2 . What is the horizontal component of the skier’s acceleration (perpendicular to the direction of free fall)? Answer in units of m/s^2.
October 8, 2012

physics
How long does it take a rocket to change its velocity by 57 m/s while accelerating at 53.7 m/s2? Round your answer to 2 decimal places.
October 8, 2012

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