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October 30, 2014

Posts by help


Total # Posts: 921

CHEMISTRY
Determine the heat of combustion of acetylene (C2H2).
April 10, 2011

chemistry
A 6.58g sample of compound was placed in a 12.6 L container. At 25.0*C, the pressure was found to be 0.75 atm. what is this compound?
April 7, 2011

math
Ben can complete 4 math problems in 20 minutes. If he continues working at the same rate, how long will it take Ben to complete 17 math problems?
April 5, 2011

8th grade math
If two numbers are relatively prime, what is their LCM? Explain your reasoning and give 2 examples supporting your answer.
March 30, 2011

8th grade math
The denominator of a fraction is 4 more than the numerator. If both the denominator and the numerator are increased by 1, the resulting fraction equals ½. What is the original fraction?
March 30, 2011

physics
This is wrong. The 0m/s should be with the mass of the target, not of the arrow.
March 28, 2011

maths
height=6 feet length=5 feet breadth=4 feet volume of the container=120 cubic feet how do you convert it into litres?
March 23, 2011

maths
height=6 feet length=5 feet breadth=4 feet what is the volume of the container in liters?
March 23, 2011

Math
there are 3 red marbles , 3 blue marbles and 1 green marble in a bag. A marble is drawn at random from the bag and not replaced. Then a second marble is drawn. What are all the possible outcomes?
March 3, 2011

Math
Is it b
March 2, 2011

Math
A triangle has 2 angles that measure 60 each. Which of the following best describes thiz triangle. A. Right isoseles triangle B. Equilateral triangle C. Obtuse isosceles triangle D. Acute scalene triangle
March 2, 2011

Math
Every morning Leah runs about 5/8 mile. At this rate, about how many miles does leah run in 2 weeks?
February 16, 2011

Math
Find two numbers with a sum of -8 and a difference of 4. Let x be the greater number and y be the lesser number?
February 15, 2011

MATH
Describe the advantages and disvanteges of seeing a rule for a function rather than listing a function values in a table
February 13, 2011

Pre-A;lgebr
Write a rule for the linear function with slope m and y-intercept b. m= -1/3, b= -2
February 13, 2011

chemistry
The total pressure in a 11.3 L automobile tire is 44 psi at 11°C. By how much does the pressure in the tire rise if it warms to a temperature of 29°C and the volume remains at 11.3 L?
February 10, 2011

Math
y= 3/5x - 6 x= 4
February 7, 2011

physics
A diver springs upward from a board that is three meters above the water. At the instant she contacts the water her speed is 9.30 m/s and her body makes an angle of 83.0° with respect to the horizontal surface of the water. Determine her initial velocity, both magnitude ...
February 7, 2011

Algebra
have no idea how to do this... divide and write your answer WITHOUT exponents. -11.2 x 10^-7 _______________ = 1.6 x 10^-2
February 5, 2011

writing
so i have to write a research paper(3-4 pages) on this topic 'does lack of sleep affect heart rate' how do i do that...this is the first time i write a research paper so i need help..thanks
February 5, 2011

physics
The engines of a 1.20 x 10^5 N rocket exert an upward thrust of 2.00 x 10^5 N for 1.50 minutes upon lift off. What is the impulse exerted on the rocket? What is the velocity of the rocket at the end of the 1.50 minute period? physics - bobpursley, Thursday, February 3, 2011 at...
February 3, 2011

physics
I don't understand where the 90 comes from
February 3, 2011

physics
The engines of a 1.20 x 10^5 N rocket exert an upward thrust of 2.00 x 10^5 N for 1.50 minutes upon lift off. What is the impulse exerted on the rocket? What is the velocity of the rocket at the end of the 1.50 minute period?
February 3, 2011

Chemistry
Hydrogen gas has been suggested as a clean fuel because it produces only water vapor when it burns. If the reaction has a 95.4% yield, What mass of hydrogen forms 94 Kg of water?
February 3, 2011

Chemistry
Maxine is studying about electrolytes in her chemistry class. The teacher asks her to test 4 different solutions to determine how well each one conducts electricity. which solution will best conduct electric current? a) HC2H3O2 b) C2H5OH c) KOH d) H2O2
February 3, 2011

chemistry
Calculate the moles of Cl atoms in 0.0565g of C2H4CL2 i got 6.87 x 10^20 mol Cl atoms <-- is that right?
February 3, 2011

Physic
How does doubling the mass of one object and tripling the distance between another object change the gravitational force betweem them? FG = G M1 M2 / r2 a. Force changes by 2/3 b. Force changes by 2/9 c. Force increases by 9 d. Force decreases by 3 e. No change in force
February 2, 2011

psychology
the question: Some size/distance cues are useful for distant objects, others for close objects. Provide one example of a cue that would be good for near objects, and one for distant objects. Explain why the cues you have selected would be less useful for objects at other ...
February 2, 2011

Math
Is the price of a piece of cloth a function of the length of the cloth? Explain
January 31, 2011

Math
Is the price of a piece of cloth a function of the length of the cloth? Explain
January 31, 2011

physics
Two point charges, 4.0×10-6 C and -1.0×10-6 C, are located on the x axis at = -1.0 cm and = 3.0 cm. (a) Determine the electric field at the origin. (b)Determine the x coordinate of a point on the positive x axis where the electric field is zero; i.e., a test charge...
January 30, 2011

physics
Inside a perfect conductor 1)the electric potential is zero throughout, even at the surfaces. 2)the electric field is zero throughout, even at the surfaces. 3)the electric potential is constant throughout, even at the surfaces. 4)none of the above is correct. I have no idea??
January 25, 2011

physics
Never mind I figured it out:)
January 23, 2011

physics
A charge Q = -520 C experiences a downward force of 0.04 N. What is the electric field in N/C at the point where the charge is located? Take upward to be positive. I know that E=Kq/r^2 therefore E= (9.0*10^9Nm)(-520*10^-6c)/r^2 I'm not sure how to get the distance and what...
January 23, 2011

Algebra
find the measure of an angle whose supplement measures two times its measure
January 22, 2011

Math
is 1/2 2?
January 5, 2011

Math
1/2x > -3
January 5, 2011

Math
-3x < 0
January 5, 2011

Math
What happens to the inequality symbol when you do the following to each side of an inequality? 1. Subtract a negative number
January 5, 2011

Math
1/2x > -3
January 5, 2011

Math
18 < -2m would the anser be m < -9?
January 5, 2011

Math
A truck tire travels about 11 feets in 1 full rotation. What is the diameter of the wheel, to the nearest inch?
December 16, 2010

physics
A 1300 sports car accelerates from rest to 95KM/H in 7.0S .What is the average power delivered by the engine?
December 15, 2010

chemistry
what is the total number of joules released when a 5.00 gram sample of water changes from liquid to gas at 100 degrees Celsius?
December 15, 2010

physics
Assume that the pressure is one atmosphere and determine the heat in joules required to produce 3.23 kg of water vapor at 100.0 °C, starting with (a)3.23 kg of water at 100.0 °C and (b)3.23 kg of liquid water at 0.0 °C
December 14, 2010

physics
A piece of glass has a temperature of 72.0 °C. Liquid that has a temperature of 37.0 °C is poured over the glass, completely covering it, and the temperature at equilibrium is 50.0 °C. The mass of the glass and the liquid is the same. Ignoring the container that ...
December 13, 2010

Physics
A cube of solid aluminum has a volume of 1.00 m^3 at 20 degree C. What temperature change is required to produce a 100-cm^3 increase in the volume of the cube? I know you are supposed to use: DeltaV=Beta*Vo*DeltaT. But I don't know what Beta is and the ones I have found ...
December 12, 2010

PHYSICS
A toy car in the figure below runs off the edge of a table that is h = 1.375 m high. The car lands d = 0.375 m from the base of the table.How fast was the car going on the table?
December 11, 2010

PHYSICS
You accidentally throw your car keys horizontally at 10.0 m/s from a cliff 78 m high. How far from the base of the cliff should you look for the keys?
December 11, 2010

physics
an arrow of mass .04 kg is pulled back 10 cm in the bow, having a force of 25.2 N. It is released 1.5m from the ground...how far will the arrow fly? (all of the energy from pulling it back converts into the flying arrow)
December 6, 2010

Physics
Rubber Band A 156 g hockey puck is attached to a rubber band and rotated with an angular speed of 9.8 rad/s on frictionless horizontal ice. It takes a force of 1.12 N to stretch the rubber band by 1 cm. (a) If the original length L of the rubber band is 1 m, by how much (in m...
December 3, 2010

chemistry
thanks for the explanation!!!
December 1, 2010

chemistry
2. A 350 mL buffer solution containing 0.15 M HF and 0.150 M NaF is reacted with sodium hydroxide. What mass of NaOH can this buffer neutralize before the pH rises above 4.0? If the same volume of buffer was 0.35 M in HF and 0.35 M in NaF then what mass of NaOH could be ...
December 1, 2010

chemistry
For each of the following solutions, calculate the initial pH and the final pH after adding 0.010 mol of HCℓ. a) 500.0 mL of pure water i'm not sure how to do this question.. would the equation be h20+h30 equilibrium arrows h30+h20
December 1, 2010

physics
A 910 kg sports car slows down to 6.0 m/s to read a cross street sign. The 1440 kg pick-up truck following the sports car fails to see that the sports car has slowed and continues traveling at 17.0 m/s. The pick-up slams into the sports car. With what velocity will the two ...
November 29, 2010

physics
i read the question wrong..thank for the help
November 29, 2010

physics
A 45.00 kg child standing on a frozen pond throws a 0.60 kg stone to the east with a speed of 5.80 m/s. Neglecting friction between child and ice, what is the speed (in m/s) of the child after throwing the stone? I'm kind of confused about the masses..
November 29, 2010

CAL 1
DERIVATIVE f(x)=4t+1 (x,x+2)
November 28, 2010

cal 1
Find the area of the indicated region f(x)=(4-x^2) between(0,2)with 4 equal subintervals (left endpoints)
November 27, 2010

math
find all points on the hyperbola y=1/x, that are closest to the origin on (1/2,2)
November 27, 2010

cal 1
f(x)= (1-sinx) interval (0≤x≤2π) find where the function is increasing decreasing.. i know that f`(x)=1-sinx it is equal to zero when x=pi/2 im stuck there..
November 26, 2010

chemistry
oops..i posted this question twice
November 25, 2010

chemistry
a 5.55g sample of a weak acid with ka=1.3*10^-4 was combined with 5.00ml of 6.00 M NAOH and the resulting solution was diluted to 750mL. The measured pH of the solution was 4.25. what is the molor mass of the weak acid. if used the formula pH=kpa+log(base/acid) Ph=3.89+log(6....
November 25, 2010

chemistry
a 5.55g sample of a weak acid with ka=1.3*10^-4 was combined with 5.00ml of 6.00 M NAOH and the resulting solution was diluted to 750mL. The measured pH of the solution was 4.25. what is the molor mass of the weak acid. if used the formula pH=kpa+log(base/acid) Ph=3.89+log(6....
November 25, 2010

chemistry
A 20ml sample of .125M diprotic acid solution was titrated with .1019M KOH.the constants for the acid are k1=5.2*10 ^-5 and K2=3.4*10 ^-10. What added volume of base does each equivalence point occur? i got .0254L for the first one and .0508 for the second. Can anyone check if...
November 24, 2010

physics
What is the original compression distance of the spring? Thought it would be zero but that isn't right.
November 23, 2010

physics
a 3.5 kg block is accelerated from rest by a compressed spring of spring constant 640 N/m. The block leaves the spring at the springs relaxation length.The block then travels over a horizontal floor with coefficient of kinetic friction 0.25. The friction force stops the block...
November 23, 2010

physics
never mind i got the question:)
November 23, 2010

physics
A 2.606 kg block is on a horizontal surface with ìk = 0.160, and is in contact with a lightweight spring with a spring constant of 577 N/m which is compressed. Upon release, the spring does 7.212E-1 J of work while returning to its equilibrium position. I found the ...
November 23, 2010

physics
the next part is What is the speed of the block when it hits the spring? i did 1.42=.5mv^2(final)-.5mv^2(initail) The final velocity woulf be zero so 1.42=.5(2.8)v^2 v=1.01 im not sure what i did wrong
November 23, 2010

physics
A moving 2.8 kg block collides with a horizontal spring whose spring constant is 215 N/m (see figure). The block compresses the spring a maximum distance of 11.5 cm from its rest position. The coefficient of kinetic friction between the block and the horizontal surface is 0.48...
November 23, 2010

physics
The force F = (3.2, -7.1) N acts on a mass of 1.15 kg. At time t = 0 s, the mass has a velocity v0 = (-0.46, 0.36) m/s. What is the initial kinetic energy (in J)? i know that k=.5mv^2 so the answer i got was (.12167,0.07452) but i'm not sure what to do from there?
November 22, 2010

physics
The force F = (3.2, -7.1) N acts on a mass of 1.15 kg. At time t = 0 s, the mass has a velocity v0 = (-0.46, 0.36) m/s. What is the angle (in degrees) of the initial velocity, measured counter-clockwise from the +x-axis? I got 38.04 degrees but isn't the right answer
November 21, 2010

physics
A 2.20 kg box slides down a rough incline plane from a height h of 1.39 m. The box had a speed of 2.77 m/s at the top and a speed of 2.34 m/s at the bottom. Calculate the mechanical energy lost due to friction
November 21, 2010

physics
A constant force of 48.7 N, directed at 34.1° from horizontal, pulls a mass of 15.1 kg horizontally a distance of 2.77 m. Calculate the work done by the force.
November 21, 2010

math
A painter leans a ladder against a vertical wall. The top of the ladder is 7 meters above the ground. When the bottom of the ladder is moved 1 meter farther away from the wall, the top of the ladder is 5 meters above the ground. What is the length of the ladder? Round to the ...
November 17, 2010

math
Three rectangles have exactly the same area. The dimensions of each rectangle (as length and width) are a and b; a – 3 and b + 2; and a + 3 and b – 1. Find the area of the rectangles.
November 17, 2010

math
Three rectangles have exactly the same area. The dimensions of each rectangle (as length and width) are a and b; a – 3 and b + 2; and a + 3 and b – 1. Find the area of the rectangles.
November 17, 2010

Physics
A cylinder with a piston is filled with ideal gas. The gas temperature is held at 450 K. The cylinder is heated by an oven through a square metal rod connected between the oven and the cylinder. The rod has sides d = 2 cm and length L = 2.3 m. (a) If the oven is held at 850 K...
November 16, 2010

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 plese 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 dont 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

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