Monday
September 1, 2014

Posts by K


Total # Posts: 741

engineering maths
Show that the following curves are intersect eachother orthoganally.r-(1+coso) r-(1-coso)
August 31, 2014

World Geography
A. was the correct answer.
August 1, 2014

World Geography
19.With respect to human rights issues in Southeast Asia, which statement is most accurate? A.Both Cambodia and Vietnam carried out ethnic eradication programs against hill people. B.Chinese merchants living in Cambodia and elsewhere have carried out vendettas against hill ...
August 1, 2014

chemistry
A block of copper of unknown mass has an initial temperature of 66.7 ∘ C . The copper is immersed in a beaker containing 95.5g of water at 20.6 ∘ C . When the two substances reach thermal equilibrium, the final temperature is 26.0 ∘ C .What is the mass of the...
July 2, 2014

math
At Dora's donut shop, dora makes 15 different varieties of donuts. Seven of these varieties are filled with jelly or cream. Officer sweetooth was sent to dora's shop to choose a dozen donuts, all different, with six filled and six unfilled. How many different ...
June 8, 2014

math
Indicate whether the following statement is true or false. If a figure can be translated, then it will tessellate. I say false am I right?
May 19, 2014

physics
an electron in the second energy level absorbs a photon of energy 6 ev what's the speed of the ejected electron? I have tried to manipulate and use the kinetic energy equation, c= lamba x f, and many other ways, but I don't know why can't get the answer, which is v...
May 18, 2014

math
Use integers from-3 to 3 to graph the equation. y=1/3|x|-2. Please help me how it would be on a graph
May 18, 2014

math
I forgot to put use the integers -3 to 3 to graph the equation.
May 18, 2014

math
What would a graph look like with the equation y=-2(x)2+3.the two next to the x means to the second power. Please help me
May 18, 2014

math
Your description helped me understand thank you. It is D
May 17, 2014

math
Is it A
May 17, 2014

math
The vertices of ABC are A(2,-5), B(-3,5), and C(3,-3).the triangle is reflected over the x-axis.use arrow notations to describe the original triangle and its reelection. A) A(2,-5),B(-3,5),C(3,-3)->(2,-5),(-3,5),(3,-3) B) A(2,-5),B(-3,5),C(3,-3)->(-2,5),(3,-5),(-3,3) C) ...
May 17, 2014

math
Can't you just tell me if its a,b,c, or d? I'm stressed out please
May 17, 2014

math
The point C(3,-1) is translated to the left 4 units and up 1 unit.write a rule to describe the translation.what are the coordinates of the image point? A) (x,y)->(x+4,y+1);(7,-2) B) (x,y)->(x-4,y-1);(-1,0) C) (x,y)->(x+4,y-1);(7,0) D) (x,y)->(x-4,y+1);(-1,0) Is it d
May 17, 2014

math
what is the correct description for the translation of A to A? A(10,3)->A(1,6) a) right 9; up 3 b) left 9; down 3 c) right 9; down 3 d) left 9; up 3 Is it C
May 17, 2014

math
y=1/3|x|-2 use integer values of x from-3 to 3 to graph the equation. Please help me graph this
May 17, 2014

math
y= -2x+3.the x has a 2 above it
May 17, 2014

math
I'm only in seventh grade and I don't understand any of this.what does a parabola look like
May 17, 2014

math
y=2x^+3 use integer values of x from -3 to 3 to graph the equation. Someone please tell me how to graph this
May 17, 2014

Alg
order your answers from smallest to largest x, then from smallest to largest y. If there is no solution, enter NO Solution 2x^2+3y^2=48 x^2-y^2=4 (x,y)= ( , ) (, ) (x,y)= ( , ) (, ) (x,y)= ( , ) (, ) (x,y)= ( , ) (, )
May 2, 2014

statistics
Data were collected on 100 students regarding their class and major. The data are summarized in the following contingency table. What is the probability of randomly selecting a sophomore or an undeclared student?
April 23, 2014

Alg
A car with good tread can stop in less distance than a car with poor tread. A model for the stopping distance d, in feet, of a car with good tread on dry cement is d = 0.04v2 + 0.5v, where v is the speed of the car in miles per hour. If the driver must be able to stop within ...
April 16, 2014

graphing
(0,-2)is the vertex- what is the domain and range??? State the domain and range of the function. (Enter your answers using interval notation.)
April 11, 2014

Intermediate algebra
Can you show the work of how to work this word problem ? A local electronics store will sell 7 ax adapters and 2 rechargeable flashlights for $86 or 3 ac adapters and 4 rechargeable flashlights for $84. What is the price of a single ax adapter and a single rechargeable ...
February 21, 2014

Chem; States of Matter
Thanks! My book suggests that: Steam = [[(175)(4.18)(100)] /1000] + 175(1mol/18.015)(-40.7/1mol) Where -40.7 is the Hvap ... I think. So I'm still super lost with that one weird extra step! Everything else is the same!
February 11, 2014

Chem; States of Matter
To an insulated container with 100.0 g H2O (l) at 20.0 degrees C, 175 g steam at 100.0 degrees C and 1.65 kg of ice at 0.0 degrees C are added. a) What mass of ice remains unmelted after equilibrium is reached? b) what additional mass of steam should be introduced into the ...
February 11, 2014

Chemistry
For example, when a question asks about two equivalents of bromine, does that mean Br2 OR 2Br2? Thanks
January 20, 2014

Chemistry
Thanks :) so just to be clear, does it matter what the Mg is reacting with, or is it always going to have the coating of the MgO on it?
January 15, 2014

Chemistry
When a student doesn't polish a sample of Mg ribbon before massing it, what happens when calculating the molar volume? Is it that the Mg ribbon doesn't completely react therefore less volumes of gas are produced?
January 15, 2014

Chemistry
How would you define pressure in the unit of thermodynamics? Is it just a force basically?
January 10, 2014

physics
I think it would just be Fg x m, so 70kg times 9.81 m/s^2, and then multiply all of that by 2.9m, and the negative is just saying what direction the man is falling, meaning downwards
January 10, 2014

BUSINESS
Do you believe economic principles like competition apply in both private and public organizations? Why?
January 9, 2014

Science
suppose that a population of skunks lives on an isolated island is 500 skunks are present today and the birth rate is 65 per week and the death is 47 per week how many skunks to you predict will be on the island 105 days from now and what would a graph population versus time ...
December 22, 2013

chemistry
ok, so i did a lab called: measurements using electrochemical cels and electroplating, and one of the post lab questions asks,if the student fails to dry the electrode, in this case (Cu+2), what effect does it have on the calculated value of Faraday? and what affect does it ...
December 12, 2013

Chemistry
how can you tell if something with oxidize or reduce some other thing, based on the standard reduction potential table?
December 11, 2013

Chemistry
how can you tell if something with oxidize or reduce some other thing, based on the standard reduction potential table?
December 11, 2013

Chemistry(DrBob222)
thanks for your help :)
December 9, 2013

Chemistry(DrBob222)
the procedure is no more precise really, I understand the lab, if i can ask a different question then, when delta g is negative and becoming less negative (or more positive), why is this happening over a decrease in temperature (increase in volume)
December 9, 2013

Chemistry(DrBob222)
yes I understand, and this helps a lot, but what I don't understand, is why in one trial the delta s was higher than in another trial, could you explain why that happened?
December 9, 2013

Chemistry(DrBob222)
it went back up to 116.4*
December 9, 2013

Chemistry(DrBob222)
So, i did this lab, a solubility and thermodynamics lab of KNO3, and in it we had to determine the delta h delta g and delta s, the question i have is what is the relationship of the signs delta h, delta s, and delta g, to the dissociation of the salt and the temperature ...
December 9, 2013

Chemistry(DrBob222)
for a thermodynamics lab, I have to graph the ln K vs. 1/T, so does the ln K go on the y-axis and the 1/T go on the x-axis?
December 8, 2013

AP Chemistry
for a thermodynamics lab, I have to graph the ln K vs. 1/T, so does the ln K go on the y-axis and the 1/T go on the x-axis?
December 8, 2013

Physics help please
A crate is dragged 5.0 along a rough floor with a constant velocity by a worker applying a force of 125N to a rope at an angle of 30degrees to the horizontal. Calculate the work done by the tension in the rope, the force of friction, and the net force. I know the work don on ...
December 5, 2013

Chemistry (DrBob222)
Is the relationship between delta G and Temperature inverse or direct?
December 4, 2013

AP US History
When the south Carolina seceded in 1860 they seceded because Abe Lincoln was elected president. But, is the secession of South Carolina also an example of state's rights? if so, how?
December 3, 2013

physics
A 70.5kg football player is gliding across very smooth ice at 2.05m/s . He throws a 0.470kg football straight forward. What is the player's speed afterward if the ball is thrown at 14.5m/s relative to the ground? What is the player's speed afterward if the ball is ...
December 3, 2013

chemistry (Dr.Bob222)
Ok, so when doing a serial dilution, would you day that the first well with no ppt represents a perfectly saturated solution, why or why not?
November 25, 2013

chemistry (Dr.Bob222)
Do serial dilutions start out as saturated solutions?, Meaning when it starts out ppt forms, but there is a point where ppt stops forming, so when the ppt stops forming does that mean it is representing a saturated solution, and that when the ppt is not forming the solution ...
November 25, 2013

Physics
A fire truck attaches two fire hoses to a hydrant to fight a fire. Each hose has a diameter of 20 cm. The underground water pipe going to the hydrant has a diameter of 100 cm. In the underground pipe, the water has a speed of 2.0 m/s.
November 22, 2013

Please help!- Physics
i dont get it
November 22, 2013

Chemistry(Dr.Bob222)
Does the [H+]=[OH-] at the midpoint or the equivalence point?
November 20, 2013

Chemistry(Dr.Bob222)
What does it mean for something do to be neutralized? Is that when the [H+]=[OH-]? or is that totally wrong?
November 20, 2013

History Quote
“Man is not made better by being degraded; he is seldom restrained from crime by harsh measures, except the principle of fear predominates in his character; and then he is never made radically better for its influence.” - Dorothea Dix What exactly does this quote mean?
November 17, 2013

Algebra
Remove the parentheses from the following expression, and combine like terms: 3(ax + b2 – c) + 2 22 A. –3(ax – b2 + 3c – 6 B. 3ax +3b2 – 3c + 2 C. 3(ax + 3b2 – 3c + 6 D. (ax + b2 – c + 5
November 15, 2013

Math
What is a 2 step equation that equals 8 ?
November 7, 2013

Chemistry (Dr.Bob222)
Ok thanks, yes that answer was right, thanks so much for explaining the equation to me, it makes total sense now!
November 7, 2013

Chemistry (Dr.Bob222)
Just Kidding I got 46.51, but that is not one of the answer choices, so which would I pick? or did I do it wrong?
November 7, 2013

Chemistry (Dr.Bob222)
ok, so I got 3.32, so would I just multiply that by the half-life? Because the answer choices are 28 days, 14 days, 42 days, 56 days, and 70 days
November 7, 2013

Chemistry (Dr.Bob222)
The half-life of P-32 is 14 days. How long after a sample is delivered can a laboratory wait to use a sample in an experiment if they need at least 10 percent of the original radioactivity? I need help on how to set up this problem. What is the general equation to use for a ...
November 7, 2013

Chemistry (Dr.Bob222)
How can you tell if a salt is neutral? Like the examples you gave: NaCl, KCl and KNO3, how do you know their anions or cations won't hydrolyze
November 2, 2013

Chemistry (Dr.Bob222)
The generic equation: Base− + H2O -> HBase+ OH− can be used to account for the pH of which salt? 1)CaI2 2)NH3 3)KCN 4)Al(NO3)3 5)NaCl Ok, so I know NH3, won't work because it is not a salt. The answer is KCN, but I don't understand why, could you explain...
November 2, 2013

Chemistry (Dr. Bob222)
How can you tell if something is highly concentrated or lowly concentrated? For example: H2CO3, H+, HCO3-, CO3(2- charge), is in order of highest concentration to lowest concentration, can you explain why it is that order? Thanks for your help :)
November 2, 2013

physics
A flower pot is thrown out of a window with a horizontal velocity of 8 m/s. If the window is 1.5 m off the ground, how far from the window does it land?
October 28, 2013

Chemistry
Hello Dr. Bob, I'm also having issues with a similar problem. I was able to calculate the XAr, but am unable to find the correct answers for H2 and N2, can you please help this Blake kid and I out? My book shows no problems of this sort, in order for me to work out and i&#...
October 16, 2013

Chemistry help (DrBob222)
ok will do, I just honestly had no idea how to do this. Can you explain how you got "2012 kJ/5*32 g oxygen. Therefore, for 320 g (10*32 g O2) you will get (2012 kJ/160) x 320 = ? " this part? thanks :)I don't understand where the grams came from, like I know it ...
October 15, 2013

Chemistry help (DrBob222)
propane (c3h8) is burned in oxygen to produce carbon dioxide and water. The heat of combustion of propane is -2012 kJ/mole. How much heat is given off when 3.0 mol C3H8 are react with 10.0 mol O2? Thanks, and please if possible show all steps!
October 15, 2013

algebra
-48x^3 + 32x^2 -8x
October 12, 2013

chemistry (DrBob222)
A student fails to fill the cuvette 2/3 full with the reaction mixture ( CV+ and OH-). What effect does this error have on the measured absorbance values? Thank you :)
October 9, 2013

chemistry (Dr.Bob222)
In a reaction, if the concentration decreases faster, that means the reaction has a larger rate constant, and a faster reaction, and a shorter half-life. Is that a correct statement? If not, please correct me, thanks for your help :)
October 2, 2013

Physics Changing Acceleration
Derive position, velocity, and acceleration kinematics equations for an object undergoing a changing acceleration? I understand that somehow we need to get (∆a/∆t) as the change in acceleration into the kinematic equations but I really don't know where to start.
September 28, 2013

Physics (pls help mr.bobpursley or drbob222)
A block is resting on top of a rough incline with coefficients of kinetic and static friction of 0.25 and 0.45 respectively. The angle of the incline is gradually increased until the block just begins to slip. How long will it take the block to slide to the bottom of the ...
September 16, 2013

chemistry
We have to mixed 2 hydrated compounds each in a separate beaker filled with water, and then dump one of the solutions into the other and mix that, then filter the 1 solution out, so that the precipitate is caught in a filter paper, and the water is caught in an erlynmeyer ...
September 15, 2013

chemistry
So I did an experiment at school in which we had to form 2.00 grams of precipitate by mixing 2 hydrated compounds. So for the products, obviously one of it is water, and the other 2 products are compounds, one of which, is insoluble. So when I measured the amount of ...
September 15, 2013

chemistry
Oh! That makes much more sense, so the chemical factor is used to keep the atom of interest equal, which in this case was the Fe, and when we look at the atom of interest we don't need to worry about the rest of the formula being balanced, meaning in the example, as long ...
September 5, 2013

chemistry
So the bottom line is, that the chemical factor is used to make the amount of atoms equal?
September 5, 2013

chemistry
So when you wrote the balanced equation, how did you know that you had to add O2 in the equation? Thanks, sorry for the trouble
September 5, 2013

chemistry
Why is the molar mass of Fe3O4 being multiplied by 2? and why is the molar mass for Fe2O3 being multiplied by 3? Thanks
September 5, 2013

chemistry
An ore contains Fe3O4 and no other iron. The iron in a 38.9-gram sample of the ore is all converted by a series of chemical reactions to Fe2O3. The mass of Fe2O3 is measured to be 12.5 g. What was the mass of Fe3O4 in the sample of ore? Please show all work, not just the ...
September 5, 2013

chemistry
Haha ok, thanks :)
September 5, 2013

chemistry
Isn't it 2 moles of KCL, from the balanced equation? for the 2nd step (mole ratio)
September 5, 2013

chemistry
A 1.24 gram sample of potassium chlorate was heated with manganese dioxide until no addition reaction was visible. THe potassium chloride residue was found to be .72 grams. What was the mass of the oxygen evolved in the experiment? If there is a balanced equation, if you could...
September 5, 2013

chemistry
Those are not the right answers
September 2, 2013

chemistry
A solution is 40% acetic acid by mass. The density of this solution is 1.049 g/mL. Calculate the mass of pure acetic acid in 170 mL of this solution at 20 C. Answer in units of g The density of a solution of sulfuric acid is 1.29 g/cm3 and it is 38.1% acid by mass. What volume...
September 2, 2013

US History
What is the Puritan concept of "calling" and how does it relate to the Puritan beliefs? Thanks for you help :)
September 1, 2013

Physics
A car travels in a straight line with an average velocity of 80 km/hr for 2.5 hours and then with an average velocity of 40 km/hr for 1.5 hours. a. Calculate the largest displacement for the 4-hour trip. b. Calculate the largest average velocity for the total trip in ...
August 28, 2013

Health
d is wrong
August 22, 2013

Chemistry
A volume of 150mL of 0.35M HCl is to be prepared from 80% HCl stock solution. (Density of HCl = 1.191g/mL). Calculate the molarity of 80% HCl stock solution.
August 9, 2013

Physics
A 1.0 x 10^3 kg elevator carries a maximum load of 800.0 kg. A constant frictional force of 4.0 x 10^3 N retards the elevator's motion upward. What minimum power, in kilowatts, must the motor deliver to lift the fully loaded elevator at a constant speed of 3.0 m/s? Please ...
July 7, 2013

reproduction
why doesn't a women body reject the sperms since it is an external organism , instantly i.e, it should have produced the antibodies against it right?
June 28, 2013

Physics
thank you a lot
June 25, 2013

Physics
A small coin is inside a bowl. The bowl is a surface of revolution of the curve y=100x4 m−3. This coin slides around the inside of the bowl at a constant height of y=0.01 m above the bottom of the bowl. What is its angular velocity in rad/s? please just say the method , ...
June 25, 2013

Physics
how do we calculate speed ? time i know
June 24, 2013

maths
A ship is sailing due east at 18 knots runs into a 3 knot current moving 40 East of North. The resultant speed an direction of the ship are:
June 20, 2013

math
Explain, please?
June 7, 2013

chemistry
Thank you Dr. Bob
June 4, 2013

chemistry
Ok, so using Le Chatelier's Principle If you add heat to an exothermic reaction, the equilibrium will shift to the left. If you remove heat to an exothermic reaction, the equilibrium will shift to the right. What is it for an ENDOTHERMIC reaction? If you add a substance, ...
June 4, 2013

Finance
What does "loan amortization requirements" mean?
May 31, 2013

Chemistry
Yes, so in other terms, you are saying that exothermic reactions usually generate more, but endothermic reactions store more?
May 31, 2013

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