Friday

February 24, 2017
Total # Posts: 1,950

**chemistry**

just a guess but would all but C be stable?

*December 4, 2012*

**chemistry**

A magic number is the name given to certain numbers of protons or neutrons that have a high correlation to stability in nuclei. Magic # of protons: 2,8,20,28,50,82 Magic # of neutrons: 2,8,20,38,50,82,126, 184 Using general trends, predict the stability of the following nuclei...

*December 4, 2012*

**calculus**

1. (30 points) Consider a manufacturer whose total cost of producing x items is given by c(x)=10000+5x+1/9x^2. a. What is the average cost function A(x)= c(x)/x? b. How many items should the manufacturer produce in order to minimize average cost? c. What is the smallest ...

*December 3, 2012*

**physics**

An object is projected upward from the surface of the earth with an initial speed of 2 km/s. The acceleration of gravity is 9.81 m/s^2. Find the maximum height it reaches. Answer in units of km.

*November 30, 2012*

**Math**

A rectangle area spans . The length must be 20ft more than the width. What are the dimensions?

*November 30, 2012*

**physics**

Wow thank you so much! This problem has been bothering me for a week now

*November 30, 2012*

**physics**

A hydraulic brake system is shown. The area of the piston in the master cylinder is 6.32 cm^2, and the area of the piston in the brake cylinder is 1.83 cm^2. The coeﬃcient of kinetic friction between the brake shoe and the wheel drum is 0.443. How large is the ...

*November 30, 2012*

**Math**

When rolling two dice, what is the probability that the sum is 7 given that one die is a 5?

*November 29, 2012*

**college physics**

A hydraulic brake system is shown. The area of the piston in the master cylinder is 6.32 cm^2, and the area of the piston in the brake cylinder is 1.83 cm^2. The coeﬃcient of kinetic friction between the brake shoe and the wheel drum is 0.443. How large is the ...

*November 29, 2012*

**chem**

pH= -log [H+] pH < 7 is acidic and pH > 7 is basic. for example pH= - log [1.0e-11M] pH= 11 therefore basic solution.

*November 29, 2012*

**physics**

this is a huge help! thanks again!

*November 29, 2012*

**physics**

Wow thank you. I was really lost.

*November 29, 2012*

**math**

you deposit $2200 in an account that pays 3% interest, after 15 years you withdraw, what is the balance if the interest is compounded continuously

*November 29, 2012*

**physics**

A liquid of density 1354 kg/m^3 ﬂows with speed 2.45 m/s into a pipe of diameter 0.29 m. The diameter of the pipe decreases to 0.05 m at its exit end. The exit end of the pipe is 7.82 m lower than the entrance of the pipe, and the pressure at the exit of the pipe is 1.4...

*November 29, 2012*

**Chemistry**

how do I convert moles of Cr2O3 to moles of H2CrO4? I don't understand what this means

*November 27, 2012*

**Chemistry**

3C3H8 + 20H2CrO4-> 9CO2 + 10Cr2O3 + 32H2O Suppose you want to make 1.50 g of chromium (III) oxide, how many ml of 6.25M chromic acid will you need to use if the percent yield of the reaction is 68.6%?

*November 27, 2012*

**Phoenix**

Why do you think Windows is so prevalent? What do the other systems have to offer that Windows does not? Who uses the other systems?

*November 27, 2012*

**Financial management**

what is the principle investment ? you have $1728.34 compounded daily at 3.4% and its invested for 9 years

*November 27, 2012*

**math**

for the equations y=5x+50 and y=6x+25, for how many hats will the cost be the same and what is that cost?

*November 26, 2012*

**Chemistry**

Sodium vapor lamps, use for public lighting, emits 489 nm yellow light. What energy is emitted by: a) an excited sodium atom when it generates a photon? b) 1 mole of excited sodium atoms at this wavelength?

*November 25, 2012*

**Chemistry**

This helped me with the amount in grams of Cr2O3, but what do I do with the 2nd part, the 35.0 ml of 6.26M chromic acid?

*November 23, 2012*

**Chemistry**

3C3H8 + 20H2CrO4-->9CO2 + 10 Cr2O3 + 32H2O What mass of chromium (III) oxide will be formed by complete reaction of 1.50g of propane with 35.0ml of 6.26M chromic acid?

*November 23, 2012*

**Chemistry**

a stock solution of perchloric acid is 75.5% perchloric acid and has a density of 1.67g/ml. What is the molarity of the solution?

*November 23, 2012*

**math**

How high is a wall that casts a 15ft shadow at the same time that a 4ft flag pole casts a 4ft shadow?

*November 23, 2012*

**college english**

what is a good attention getter sentence on carpal tunnel syndrome?

*November 21, 2012*

**statistics**

The reaction time of subjects to a certain psychological experiment is considered to be normally distributed with a mean of 20 seconds and a standard deviation of 4 seconds. What is the reaction time such that only 10% of subjects are faster?

*November 21, 2012*

**statistics**

The reaction time of subjects to a certain psychological experiment is considered to be normally distributed with a mean of 20 seconds and a standard deviation of 4 seconds. What is the reaction time such that only 10% of subjects are faster?

*November 21, 2012*

**statistics**

Entry to a certain University is determined by a national test. The scores on this test are normally distributed with a mean of 500 and a standard deviation of 100. Tom wants to be admitted to this university and he knows that he must score better than 70% of the students who ...

*November 20, 2012*

**Physics**

A roller coaster is initially at a height of 40 m above the ground and has an initial velocity of 15 m/s. Using conservation of energy, find the velocity of the roller coaster at a height of 5 m above the ground.

*November 19, 2012*

**Chemistry**

What mass of Uranium (in mg) is contained in 1ml of 4.55M (UO2)3(PO4)3 solution? How do I solve this? *all numbers are subscripts

*November 18, 2012*

**physics what am i doing wrong?**

I figured it out......i don't understand why no one has helped me yet in the past week

*November 16, 2012*

**physics what am i doing wrong?**

Three masses are arranged in the (x, y) plane. 3kg (0,0) 7kg (10,0) 6kg (0,3) What is the magnitude of the resulting force on the 3 kg mass at the origin? The value of the universal gravitational constant is 6.6726 × 10^−11 N · m^2/kg^2. Answer in units of N...

*November 16, 2012*

**can someone please help w/ physics?**

anybody? please?

*November 16, 2012*

**can someone please help w/ physics?**

An object of mass 154 kg moves in a smooth straight tunnel of length 2990 km dug through a chord of a planet of mass 3.19 × 10^24 kg and radius 1 × 10^7 m Find the eﬀective force constant of the harmonic motion. The value of the universal gravitational ...

*November 16, 2012*

**english**

Ms. Sue can you please check for #1 The Gerund Phrase is water skiing , sailing, and swimming Direct Object ?

*November 16, 2012*

**PHYSICS!**

An object of mass 154 kg moves in a smooth straight tunnel of length 2990 km dug through a chord of a planet of mass 3.19 × 10^24 kg and radius 1 × 10^7 m Find the eﬀective force constant of the harmonic motion. The value of the universal gravitational ...

*November 16, 2012*

**chemistry**

. What is the mass concentration (titer) is a solution of sulfuric acid with the molar concentration equivalent 0.5 mol/dm3?

*November 15, 2012*

**chemistry**

Potassium nitrate weighing 15 g was dissolved in water volume of 200 cm3. Calculate the mass fraction of KNO3 in solution.

*November 15, 2012*

**chemistry**

What is the mass of dry NaCl sample should be taken for 100 cm3 of 0.5 mol/dm3 aqueous solution?

*November 15, 2012*

**chemistry**

Determine the molality 0.8 mol/dm3 solution of Fe2 (SO) 4. Density equal to 1 g/cm3.

*November 15, 2012*

**chemstry**

What mass of sucrose must be taken for solution weight of 200 g, which is equal to molality 0.05 mol / kg?

*November 15, 2012*

**chemistry**

What mass of sucrose must be taken for solution weight of 200 g, which is equal to molality 0.05 mol / kg?

*November 15, 2012*

**social studies**

which of the following statements is supported by the information in the map please help

*November 14, 2012*

**physics**

A 11.1-kg block rests on a horizontal table and is attached to one end of a massless, horizontal spring. By pulling horizontally on the other end of the spring, someone causes the block to accelerate uniformly and reach a speed of 3.12 m/s in 1.17 s. In the process, the spring...

*November 13, 2012*

**physics**

When an object of mass m1 is hung on a vertical spring and set into vertical simple harmonic motion, it oscillates at a frequency of 14.2 Hz. When another object of mass m2 is hung on the spring along with the first object, the frequency of the motion is 3.40 Hz. Find the ...

*November 13, 2012*

**physics**

A block rests on a frictionless horizontal surface and is attached to a spring. When set into simple harmonic motion, the block oscillates back and forth with an angular frequency of 9.0 rad/s. The drawing shows the position of the block when the spring is unstrained. This ...

*November 13, 2012*

**physics**

A 82.5-kg climber is scaling the vertical wall of a mountain. His safety rope is made of a material that, when stretched, behaves like a spring with a spring constant of 1.82 x 103 N/m. He accidentally slips and falls freely for 0.739 m before the rope runs out of slack. How ...

*November 13, 2012*

**Physics**

In New Hampshire the average horizontal component of Earth's magnetic field in 1912 was 16 uT, and the average inclination or "dip" was 73 degrees. What was the corresponding mag-nitude of Earth's magnetic field?

*November 12, 2012*

**business calculus**

X=D(p)=400-p

*November 12, 2012*

**business calculus**

X=D(p)=400-p

*November 12, 2012*

**S.S. Check answers**

:D

*November 9, 2012*

**Math**

Draw two scalene triangles that are not congruent, but have exactly five sets of parts (sides and angles) that are congruent. Make a drawing that is to scale. Label yourmeasurements.

*November 8, 2012*

**Chemistry**

what mass of nitrogen dioxide (8NO2) will form by reaction of 3.50 mole of perchloric acid (13HClO4) with excess methylamine (8CH3NH2)? Answer is 99.1 g. How do you work this?

*November 6, 2012*

**Chemistry**

*answer is 4.14g

*November 6, 2012*

**Chemistry**

what mass of water will be formed by reaction of 3.50g of methylamine (8CH3NH2) with 15.0g of perchloric acid (13HClO4)? Answer is 99.1. How do you work this?

*November 6, 2012*

**Chemistry for Eng.**

delta H3: energy associated with the formation of water-ion interactions delta Hsoln: the enthalpy of solution

*November 1, 2012*

**math**

A section of the railway has a slope of about 0.73. In this section, a vertical change of 1 unit corresponds to a horizontal change of what length?

*October 31, 2012*

**AP Physics C**

An electron follows a helical path in a uniform mag-netic field of magnitude 0.300 T. The pitch of the path is 6.00 um, and the magnitude of the magnetic force on the elec-tron is 2.00x10^-15 N. What is the electron's speed?

*October 29, 2012*

**Physics: Kinematics**

A speed boat moving at 33.7 m/s approaches a no-wake buoy marker 93.3 m ahead. The pilot slows the boat with a constant deceleration of 2.9 m/s 2 by reducing the throttle. How long does it take the boat to reach the buoy? current work done: x = Vot + (1/2)at^2 93.3 = 0(t) + (1...

*October 29, 2012*

**Art 101 college**

Explain how Florence reflects the ideals of the dominant city-state and how some of the geographical, economical, social, and artistic forces shape this ideal. Use one example from Gardner’s Art through the Ages and one example from the Internet.

*October 27, 2012*

**Algebra 2**

(index of 3)square root of 3r-6(equals 3)

*October 26, 2012*

**physics**

As a result of friction, the angular speed of a wheel changes with time according to d(theta)/dt = w0 e^-(aplpha*t) where w0 and alpha are constants. The angular speed changes from an initial angular speed of 4.87 rad/s to 4.27 rad/s in 33.93s. A) Determine the magnitude of ...

*October 26, 2012*

**science**

A balloon with an initial volume of 2.8L at a temperature of 296K is warmed to 375K . What is its volume at the final temperature? (Assume constant pressure.)

*October 22, 2012*

**Chemistry**

148.6

*October 21, 2012*

**Physics**

A military helicopter on a training mission is flying horizontally at a speed of 60.0 m/s and accidentally drops a bomb (fortunately not armed) at an elevation of 350 m. You can ignore air resistance. Find the horizontal and vertical components of its velocity just before it ...

*October 21, 2012*

**Physics**

A pistol that fires a signal flare gives the flare an initial speed (muzzle speed) of 185 m/s. (a) If the flare is fired at an angle of 45° above the horizontal on the level salt flats of Utah, what is its horizontal range? You can ignore air resistance. (km) (b) If the ...

*October 21, 2012*

**Physics**

A ball is fired from the ground with an initial speed of 2.38 * 10^3 m/s (approximately seven times the speed of sound) at an initial angle of 56.0° to the horizontal. Neglect air resistance. (a) Find the ball's horizontal range.(m)

*October 21, 2012*

**fin/370**

a bond that has a 1000 par value (face value and a contract or coupon interest rate of 10.9%. the bond have a current market value of $1,120 and will mature in 10 years. the firm's marginal tax rate is 34%. the cost of captial from this debit is

*October 19, 2012*

**Chemistry**

How many photons with a wavelength of 450 nm is required to have mass of 1.25 micrograms?

*October 15, 2012*

**chemistry**

A 230 g sample of a compound contains 136.6 g of carbon, 26.4 g of hydrogen, and 31.8 g of nitrogen. The rest is oxygen. What is the mass percent of oxygen in the compound?

*October 10, 2012*

**chemistry**

Consider the following overall reaction which is experimentally observed to be second order in AB and zero order in C: AB+C -> A+BC Determine whether the mechanism below is valid for this reaction AB+ AB -> AB(sub 2) + A slow AB(sub2) + C -> AB+BC fast

*October 10, 2012*

**A.P. Environmental Sciences**

.5 grams of pure copper sulfate powder and 2L of water were used to create a copper sulfate solution with a concentration .5ppm. How was this done?

*October 10, 2012*

**chemistry**

Consider the following overall reaction which is experimentally observed to be second order in AB and zero order in C: AB+C -> A+BC Determine whether the mechanism below is valid for this reaction AB+ AB -> AB(sub 2) + A slow AB(sub2) + C -> AB+BC fast

*October 9, 2012*

**calculus**

Find the derivative of the function 1)f(t)=tan(e^2t)+e^tan2t f'(t)= [im not quite sure with this. im assuming the implicit differentiation] 2) F(t)=e^(8tsin2t) [for this one i got 2e^(8t)(4sin(2t)+cos(2t)) but it is incorrect.

*October 8, 2012*

**calculus**

well i entered it in again and now it took that first answer. i think theres a glitch with the program but thank you for showing me how you got the answers. it helps so much!

*October 8, 2012*

**calculus**

I've tried entering in 36x+1 earlier and it told me it was incorrect. I thought I did it wrong. Thanks for getting back to me.

*October 8, 2012*

**calculus**

Find an equation of the tangent line to the curve at the given point. y= (1+3x)^12 , (0,1) and find y' and y" y=cos(x^2) I got y' = -2xsin(x^2) i keep trying to get double prime but everything i try isnt working.

*October 8, 2012*

**Physics**

A circular hole in an aluminum plate is 2.725 cm in diameter at 0.000 degrees celsius. What is its diameter when the temperature of the plate is raised to 100.0 degrees celsius?

*October 6, 2012*

**algebra**

use the inequality -4t-8 is less than or equal to 12 a. t is greater than or equal to ? b. t + 4 is greater than or equal to ? c. t- ? is greater than or equal to 0 d. t + 10 is greater than or equal to ? e. 3t is greater than or equal to ? f. t/? is greater than or equal to -5

*October 4, 2012*

**physics**

The mass of the heavier block is 28 kg and the mass of the lighter blocks is 14 kg and the magnitude of the force of the connecting string on the smaller block is 24 N. Assume: g = 9.8 m/s^2 and the horizontal surface on which the objects slide is frictionless. Determine the ...

*September 28, 2012*

**physics**

Wow i definitely over thought that one. thank you so much for helping me! it means so much to me!

*September 28, 2012*

**physics**

A loaded truck can accelerate at 3.2 m/s^2 It loses its load so that it is only 0.2 as massive. By what factor must the acceleration change for the same driving force?

*September 28, 2012*

**Math (12th)**

What are the next three terms of the geometric sequence 32, -16, 8, …?

*September 27, 2012*

**Math (12th)**

7 and 12?

*September 27, 2012*

**Math (12th)**

What are the next three terms of the arithmetic sequence -18, -13, -8, -3,…?

*September 27, 2012*

**math**

One side of a rectangular garden is to be against the house. There are 80 meters of fencing material available to enclose the other three sides of the garden. Find the dimensions that will give the maximum area.

*September 26, 2012*

**math**

a chef can bake 15 pies in one hour. What is the rate in pies per minute?

*September 25, 2012*

**Grammar**

I haven't heard from you in a long time Write to me How is your family We'redoing fine in Wisconsin Spring is here and it's a lot warmer now Everyone is wearing shorts to school because it's sixty degrees I can't wait for summer You have to see my new ...

*September 25, 2012*

**Algebra**

The amount of plutonium given in a sample is determined by the function: A(t)=2.00e^-0.053 t= years How do I figure the rate of decay after four years?

*September 23, 2012*

**math**

5t-3/-2=t+3/2

*September 23, 2012*

**math**

3/2y=16/y+2

*September 23, 2012*

**calculus**

Differentiate. y = x^3/3 − x^2

*September 20, 2012*

**science**

What is the relationship between landscape and psychological well being?

*September 20, 2012*

**calculus**

Differentiate the function. S(R) = 4πR^2

*September 20, 2012*

**calculus**

Thank you so much! I didn't think to use the product rule.

*September 20, 2012*

**Science**

What concerns you have about the overall safety of the food you eat?

*September 19, 2012*

**Science**

Humans have increased their food supply by using fertilizers.

*September 19, 2012*

**algebra**

Use the information in the table. write and solve an equation that shows how many lions are in the preserve in all. then solve for the variable. Table: Age Number Cubs 18 Adolescents 14 Mature 2 Mature 7

*September 19, 2012*

**chem**

Potassium nitrate has a lattice energy of -163.8 kcal/ mol and a heat of hydration of -155.5 kcal/ mol . How much potassium nitrate has to dissolve in water to absorb 105kj of heat? Answer in kg.

*September 19, 2012*

**chem**

that's all there is unfortunately. answering just water for both gave me incorrect feedback.

*September 18, 2012*