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October 31, 2014

Posts by alex


Total # Posts: 2,655

physics
Why might it be hard for the firefighter to hold the hose steady when the water gushes out of the hose? Think about the law of conservation of momentum.
December 15, 2012

math
if a tree in a 1/2 inch scale drawing is 11 inches tall, how tall is the actual tree?
December 15, 2012

Chemistry
babol, for diffraction we need a wave, and according to de Broglie (and later experiments) any matter behave like a waves with different lengths ( depends on their energy). So actually we make a diffraction of electrons (as a waves) on a Mo surface.
December 14, 2012

Chemistry
ok, b) eV=E To get electrons behave like a waves with the same lenght as 0.561A, we need to give them some impulse p according to de Broglie eq. and E = p^2/2m..
December 14, 2012

Chemistry
and b) is a voltage, needed to accelerate electrons to get the same.. :)
December 14, 2012

EPCC
how to calculate the heat (kJ) released to thesurroundings when a 23.0 g of HCL if formed, from a CH4 + Cl2=CHCl3+3HCL
December 13, 2012

5th grade math (word problems)
Could you explain why you divided 25 by 3/5?
December 12, 2012

5th grade math (word problems)
I didn't see an answer from yesterday, so resending. Also, is there a website to explain how to solve word problems - like key phrases to look for (ex: 'in all' - add; 'what's left' - subtraction)? Here's question from yesterday: sorry,but I don'...
December 12, 2012

Chemistry - solubility, not "Methode Champenoise"
Is CO2 soluble in ethanol? I know that CO2 is nonpolar, so that means it's soluble in nonpolar solvents, but CO2 is soluble in H2O. H2O is polar. Also, if CO2 were obeying Henry's Law, would it be soluble in ethanol at a high pressure?
December 11, 2012

chemistry
In the "Methode Champenoise," grape juice is fermented in a wine bottle to produce sparkling wine. The reaction is given below. C6H12O6(aq)--> 2 C2H5OH(aq) + 2 CO2(g) Fermentation of 746 mL grape juice (density = 1.0 g/cm3) is allowed to take place in a bottle ...
December 11, 2012

5th grade math (word problems)
sorry,but I don't understand word problems - like what formula/expression to use. Here's the 1st problem: Rob practiced 3/5 of his music in 25minutes. About how long does it take to practice all of his music? I know that Rob has 2/5 left of music to practice. So, do I ...
December 11, 2012

Chemistry
In the "Methode Champenoise," grape juice is fermented in a wine bottle to produce sparkling wine. The reaction is given below. C6H12O6(aq)--> 2 C2H5OH(aq) + 2 CO2(g) Fermentation of 746 mL grape juice (density = 1.0 g/cm3) is allowed to take place in a bottle ...
December 11, 2012

math
Thank you very much. This problem was giving me too much stress.
December 10, 2012

math
Find the value of the function y=sqrt(x+1)+sin(x)-0.5, correct to 3 decimal places, when x=0.05 without the use of a calculator.
December 10, 2012

Chemistry
In the "Methode Champenoise," grape juice is fermented in a wine bottle to produce sparkling wine. The reaction is given below. C6H12O6(aq)--> 2 C2H5OH(aq) + 2 CO2(g) Fermentation of 746 mL grape juice (density = 1.0 g/cm3) is allowed to take place in a bottle ...
December 9, 2012

5th grade math (dividing fractions)
Sorry Khan, I was trying to say that I needed to solve for x in the problem: 3 divided by x over 9 = 5 and two fifths. . Steve, thanks for the answer. But, I'm still not sure how you solved for x after getting 27/x= 27/5. Did you multiply both sides by 1/27 to get x by ...
December 9, 2012

5th grade math (dividing fractions)
Hi.. I need help figuring out this problem, sovling for x: 3 divided by x/9 = 5 and 2/5 I was able to solve: x divided by 3/4 = 6 by multiplying 6 x 3/4 = 4 1/2. Just not sure how to solve the first problem. If I change 5 2/5 into mixed number,I still don't know what to do...
December 9, 2012

Fourth grade science
Students are conducting an investigation that tests the force of a magnet by using one magnet to repel a second magnet. Which tool would be needed to measure the distance the second magnet moves? A thermometer,A spring scale, A ruler, or A compass
December 7, 2012

physics
A nearsighted person has a far point located only 200 cm from his eyes. Determine the focal length of contact lenses that will enable him to see distant objects clearly. does anyone have any suggestion on how to tackle this problem?
December 6, 2012

9th garde math
Write an equation for the line with points (4,5) and (6,9). Please explain.
December 5, 2012

Geography
Is this correct? Hawaii and the Florida Keys are the only 2 states that are located south of the 25 degrees N latitude line?
December 5, 2012

Math
The kindergarten has a box of blocks.Some blocks are red,some yellow and some are blue.1/2 of the blocks are red,1/4 of the blocks are yellow and 24 of the blocks are blue.How many blocks are in the box?
December 5, 2012

science
at what altitide(height above earth's surface) would temperatures be 22 degrees C?
December 5, 2012

Algebra
You need to set up a system of equations. No one knows how many of each type of bill there is. Let t=twenties and f=fifties. t+f=36 20t+50f=1170 -20(t+f=36)=-20t+-20f=-720 20t+50f=1170 30f=450 f=15 t+15=36 -15 -15 t=21
December 5, 2012

algebra-NOW PLEASE
A boat is traveling in a river with a current that has a speed of 1.5 km/h. In one hour, the boat can travel twice the distance downstream as it can travel upstream. What is the boat's speed in still water?
December 4, 2012

Algebra
Simple. 70=7w
December 4, 2012

Algebra
[4(5)+-4]raised to 2nd (20+-4)raised to 2nd 16 raised to 2nd 256 is the answer
December 4, 2012

Trig
A population of animals oscillates annually from a low of 1300 on January 1st to a high of 2200 on July 1st, and back to a low of 1300 on the following January. Assume that the population is well-approximated by a sine or a cosine function. a. Find a formula for the population...
December 3, 2012

Chemistry Help
T=PV/nR P=0.96 V=0.045 n=0.002 g/mol R=0.082057
December 2, 2012

Chemistry Help
Using the accurate concentration that you measured in Part A (which is 14.77 ml), calculate the mass of HCl (in grams) present in a 15.00-mL sample of the acid solution, using proper dimensional analysis
December 2, 2012

College Chemistry
Using the accurate concentration that you measured in Part A (which is 14.77 ml), calculate the mass of HCl (in grams) present in a 15.00-mL sample of the acid solution, using proper dimensional analysis
December 2, 2012

Math (Calculus)
Use implicit differentiation to find the slope of the tangent line to the curve y/(x–9y)=x^6–2 at the point (1,-1/-8). Can someone please help me? I dont understand
November 30, 2012

MAth t
i d k but if youre in math course 7th grade im in too and u dont answer if u dont kno it cuzz this is one of the challenege questions teacher just mark as extra credit if u want but it really doesnt count
November 30, 2012

Math (Calculus)
A spherical snowball is melting in such a way that its diameter is decreasing at rate of 0.3 cm/min. At what rate is the volume of the snowball decreasing when the diameter is 10 cm. Can someone help & explain how to solve this question? Please.
November 29, 2012

math
Estimate a 15% tip on a taxi ride that costs $23.25.
November 29, 2012

math
72 is what percent of 480? Write and solve an equation to solve the problem
November 29, 2012

math
Jessica bought a computer for $325 and had to pay 6% sales tax. What was the total cost of Jessica’s computer?
November 29, 2012

Steveeee help plz
What is the area is square units o the region under the curve of the function f(x)=4, on the interveral from x=-1 to x=3
November 28, 2012

Steve help pleaseeeee
Two promotional stands are to be placed in an ellipse shaped room. One at each foci and are 3 units from center. If the room is 8 units wide what is the length
November 28, 2012

math
y1= sin (x) y2= (tanx) It is graphed in the interval [0, pi/2] find the integral
November 28, 2012

calculus
y1= sin (x) y2= (tanx) It is graphed in the interval [0, pi/2] find the integral
November 28, 2012

5th grade Language Arts
Thanks Ms. Sue! I have other sentences I would like to try to get right. 1. Mr. Morton, the best reading teacher in the world, taught me sentence structure. Complex: Mr. Morton taught me sentence structure = indep & best reading teacher in the world = dep 2. I left early so ...
November 26, 2012

5th grade Language Arts
I need help classifying sentences (compound, complex, compound-complex). Here's the sentence: I got in trouble so I can't go to the party, but it would have been fun. I answered it was complex which I got wrong.
November 26, 2012

Physics
Electromagnetic waves can form standing waves. In a standing wave pattern formed from microwaves, the distance between a node and an adjacent antinode is 0.63 cm. What is the microwave frequency? any help is much appreciated
November 23, 2012

physics
Linearly polarized light is incident on a piece of polarizing material. What is the ratio of the transmitted light intensity to the incident light intensity when the angle between the transmission axis and the incident electric field is (a) 30° and (b) 71°? Help! :(
November 23, 2012

physics
An object is located 16.8 cm in front of a convex mirror, the image being 11.5 cm behind the mirror. A second object, twice as tall as the first one, is placed in front of the mirror, but at a different location. The image of this second object has the same height as the other...
November 23, 2012

Physics
The two blocks in the figure below, m1 = 1.2 kg and m2 = 4.8, are connected by a massless rope that passes over a pulley. The pulley is 12 cm in diameter and has a mass of 2.0 kg. As the pulley turns, friction at the axle exerts a torque of magnitude 0.38 N·m. If the ...
November 21, 2012

Civics
1.The constitution grants the federal courts ____ in several different kinds of court cases. This gives them the authority to hear and decide cases properly brought before them. 2. The lowest federal courts are trial courts, which have ___, the authority to hear and decide a ...
November 20, 2012

physics
An open train car, with a mass of 2070 kg, coasts along a horizontal track at the speed 2.31 m/s. The car passes under a loading chute and, as it does so, gravel falls vertically into it for 3.25 s at the rate of 491 kg/s. What is the car's speed after the loading is ...
November 19, 2012

Physics
dude I have no idea what you just typed.. can you please clarify what all the variables you used stand for?
November 19, 2012

Physics
A thrill-seeking cat with mass 4.00 kg is attached by a harness to an ideal spring of negligible mass and oscillates vertically in SHM. The amplitude is 0.050 m, and at the highest point of the motion the spring has its natural unstretched length. Calculate the elastic ...
November 19, 2012

Physics
A plane drops a bomb from an altitude of 10,000m. a. Determine the time the bomb is in the air. b. Determine the velocity the bomb would have right before it hits the ground. c. Before the bomb is launched the plane has a horizontal velocity of 92m/s. Determine the distance ...
November 19, 2012

Chemistry Help
Write the net ionic equation for the reaction of calcium nitrate and sodium phosphate
November 14, 2012

Chemistry Help
If you mixed 10.0 mL of calcium nitrate and sodium phosphate, both 0.250M,which of the two would be the limiting reactant?
November 14, 2012

chemistry (molecular calculations)
If you had 78.2 grams of K, how much oxygen is needed to convert it all to K2O?
November 13, 2012

math
A material has a half-life of 12 hours. If initially there are 4 grams of the material, how much is present after 8 hours? I know the answer is 8/3, but how would you solve this using calculus? please help.
November 11, 2012

Math
Is this correct? If one card is drawn from a regular deck of cards,what is the probability the card will not be an ace? 1/13 is the probability
November 9, 2012

Math
If one card is drawn from a deck of cards,what is the probability the card will not be an ace? I think the answer is 1/13. Am I correct???
November 9, 2012

Geography
Is this correct? 1. The closest ocean to Mongolia is the Pacific Ocean. 2. The capital of the island nation that has the Sea of japan as its western border is Tokyo, Japan. Thank You
November 9, 2012

physics
A car travels in a straight line for 4.8 h at a constant speed of 57 km/h . What is its acceleration? Answer in units of m/s
November 8, 2012

Physics Help
Two compressible solids are formed into spheres of the same size. The bulk modulus of sphere two is twice as large as the bulk modulus of sphere one. You now increase the pressure on both spheres by the same amount. As a result of the increased pressure, how is the change in ...
November 7, 2012

Implicit differentiation
implicit differentiation of x^3y^2-5x^2y+x=1
November 7, 2012

Chemistry
7.0
November 3, 2012

calculus
This is the problem that I got. I thought of that too. I think that it might just be a type? x is probably suppose to be h...
November 3, 2012

calculus
Given: y^2+h^2=1 Find h as a function of y. If expression for dy/dx includes h, substitute the expression in terms of y for h. Write dy/dx in terms of y only. Show that x=[(1+sqrt(1-y^2))/y]-sqrt(1-y^2) satisfies the differential equation you found to prove this equation ...
November 3, 2012

calculus
Given: y^2+h^2=1 Find h as a function of y. If expression for dy/dx includes h, substitute the expression in terms of y for h. Write dy/dx in terms of y only. Show that x=[(1+sqrt(1-y^2))/y]-sqrt(1-y^2) satisfies the differential equation you found to prove this equation ...
November 3, 2012

Chem
The following substances undergo complete combustion in a bomb calorimeter. The calorimeter assembly has a heat capacity of 5.136 ^ C. In each case, what is the final temperature if the initial water temperature is 22.37^ C? 0.3268g caffeine, C8H10N4 (heat of combustion = -...
October 29, 2012

College Chemistry
Calculate the heat in joules needed to warm 225g of water from 88.0 degrees Celsius to its boiling point 100.0 degrees Celsius
October 24, 2012

Biology
1)Animal cells prefer to be in isotonic solution, while plant cells prefer to be in hypotonic solution. Explain what this means and why it is so. 2.) In terms of Gibbs free energy, what does “unstable” mean? Also, give at least two additional ways to say that a ...
October 24, 2012

physics
A box slides down a plane 8 m long that is inclined at an angle of 30 degrees with the horizontal. If the box starts from rest and u = 0.25, find a.) the acceleration of the box, b.) it's velocity at the bottom of the plane, and c.) the time required for it to reach the ...
October 23, 2012

Math
Sare estimated 32x45 by using 30x40. How could Sara make a more accurate estimate?
October 22, 2012

Calculus 1
Find the derivative of y with respect to x. y=(x^6/6)(lnx)-(x^6/36) So far this is what I've gotten: y=(x^6/6)(lnx)-(x^6/36) y=(1/6)x^6(lnx)-(1/36)x^6 y'=(1/6)x^5(1/x)+lnx(x^5)-(1/6)x^5 What do I do now?
October 22, 2012

CHEMISTRY
Explain Why The Addition Of An Electron To A Chlorine Atom Is An Exothermic Process And The Addition Of An Electron To A Magnesium Atom Is An Endothermic Processs
October 22, 2012

math
what is the prime factorization of 1 bilion using exponents?
October 22, 2012

Physics
Can you tell me the answer for c and d. I got the one for a and b correct but c says it's not correct. I put 21.96N.
October 21, 2012

Physics
A 2.42kg block starts from rest at the top of a 22.9◦ incline and accelerates uniformly down the incline,moving 2.41m in 2.14s. The acceleration of gravity is 9.81m/s2. a) What is the magnitude of the acceleration of the block? Answer in units of m/s2 b) What is the coe...
October 21, 2012

English
?
October 21, 2012

Chemistry
Then if it Decrease the system will shift to the side with more moles of gas?
October 21, 2012

Chemistry
I have a question about this one 2N2O(g) ⇋ O2(g) + 2N2(g), what happens to the equilibrium position if the pressure decreases? Is going to shift to the right or to the left???
October 21, 2012

Geography
5 countries in Africa with coastlines on the Atlantic Ocean and lie between 20 degrees n and 10 degrees n? I think they are guinea,guinea-Bissau,Gambia,Senegal and Mauritania. Is this right?
October 20, 2012

statistics
Given the length an athlete throws a hammer is a normal random variable with mean 50 feet and standard deviation 5 feet, what is the probability he throws it between 50 feet and 60 feet?
October 19, 2012

Physics (Difficult)
A uniform rectangular bar with cross-section 66 mm x 54 mm and of length 1.7 m has mass 16kg. It pivots about an axis prependicular to the wider face. The axis is equidistant from the edges and 170 mm from one end. What is the relevant second moment of mass?
October 19, 2012

physics
A 0.395-kg blue bead slides on a frictionless, curved wire, starting from rest at point in the figure below, where h = 1.50 m. At point , the blue bead collides elastically with a 0.650-kg green bead at rest. Find the maximum height the green bead rises as it moves up the wire.
October 18, 2012

physics
a .77 kg book with dimensions of 28.9 cm by 20.2 cm is on a table. What force does the book apply on the table?
October 17, 2012

geography
Is mexico the large north american country that the tropic of cancer cuts through?
October 17, 2012

math 7
the weight of thewater in a full bathtub in a quarter ton. How many pounds is a quarter ton/
October 17, 2012

Physics
A crank of length 190mm is initially at 65 degree above the horizontal, and rotates through 35 degree towards the horizontal. A vertically downward force of 160 N acts on the outer end of the crank. Calculate the work done by the force.
October 17, 2012

Physics
A car travels in a flat circle of radius R. At a certain instant the velocity of the car is 24 m/s west,and the acceleration of the car has componets of 2.4 m/s^2 east and 1.8m/s^2 south. Find the total displacement of the object (from t=0 to 25)
October 16, 2012

College Chemistry
We will calculate the amount of acid to use in each titration. Assume that you are using 0.0512 M NaOH(aq). A good volume of NaOH(aq) to use per titration is 15mL. From this molarity and volume, the moles of NaOH can be calculated. Since the unknown acid is monoprotic, this ...
October 15, 2012

Algebra
He isn't supposed to give you the answers. You should be greatful he helped you find them.
October 15, 2012

physics
help! Two charges A and B are fixed in place, at different distances from a certain spot. At this spot the potentials due to the two charges are equal. Charge A is 0.22 m from the spot, while charge B is 0.54 m from it. Find the ratio qB/qA of the charges.
October 11, 2012

physics
trying to study but stuck with this one. Two tiny spheres have the same mass and carry charges of the same magnitude. The mass of each sphere is 4.62 x 10-6 kg. The gravitational force that each sphere exerts on the other is balanced by the electric force. Determine the charge...
October 11, 2012

Physics
Two cars pass each other traveling at the same speed. One car has a constant velocity of 18.0 m/s east. The other car has a constant acceleration of 3.00 m/s^2, west. How much time will have elapsed until the cars are 128 m apart?
October 11, 2012

geography
Is this correct? The Caribbean Sea is the second largest sea in the world that is south of cuba.
October 10, 2012

Math
Find the limit of (2cosx+3cosx-2)/(2cosx-1)as x tends to pi/3.
October 10, 2012

phy
Integral of F(x) = .5mv^2 18x-.5(.53)x^2=.5mv^2 find v.
October 9, 2012

Chemistry
If the Kb of a weak base is 2.6 × 10-6, what is the pH of a 0.24 M solution of this base?
October 6, 2012

Chemistry
extremely easy. Sorry! pH=1 and pOH = 13
October 6, 2012

Chemistry
Calculate the pH and the pOH of an aqueous solution that is 0.025 M in HCl(aq) and 0.075 M in HBr(aq) at 25°C.
October 6, 2012

calculus
Prove (by using a point and a normal vector) that the plane whose intercepts with the coordinate axes are x=1, y=1, and z=1 is given by the equation x+y+z=1
October 4, 2012

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