Saturday

December 20, 2014

December 20, 2014

Total # Posts: 1,000

**physics**

A building has become accidentally contaminated with radioactivity. The longest-lived material in the building is strontium-90. (The atomic mass of Sr is 89.9077 u.) If the building initially contained 4.8 kg of this substance and the safe level is less than 10.0 counts/min, ...
*June 3, 2012*

**physics**

After 1.84 days, the activity of a sample of an unknown type radioactive material has decreased to 85.8% of the initial activity. What is the half-life of this material? (in days)
*June 3, 2012*

**Chemistry**

Alright, I was able to figure them all out. Thank you!
*June 1, 2012*

**Chemistry**

So for the first portion I came to Kb=1.5x10^-10 then x^2/.14-x= 1.56x10^-10 x^2-(2.2x10^-11)x - 1.56x10^-10=0 solving with the quadratic equation I came to x= 1.25x10^-5 (I'm disregarding i) So -log(1.25x10^-5)= 4.9 But somewhere I've done something wrong as the ...
*June 1, 2012*

**Chemistry**

Calculate the pH at the halfway point and at the equivalence point for each of the following titrations. (a) 100.0 mL of 0.14 M HC7H5O2 (Ka= 6.4 multiplied by 10-5) titrated by 0.14 M NaOH halfway point equivalence point (b) 100.0 mL of 0.29 M C2H5NH2 (Kb = 5.6 multiplied by ...
*June 1, 2012*

**science**

Its C...Nodules of certain plants such as clover fix Nitrogen to the soil...thats the reason farmers grow cver ...then plow it back into the soil..Natural source of Nitrogen...dontknow about the others...
*May 31, 2012*

**Introduction to Psychology**

way too much time on phone...in the shower..and on Facebook..:)
*May 31, 2012*

**Math**

Add it up...here goes..6 X $9.80...plus 1/4 hour =15 mins...so work out 1/4 of $9.80...remember 1/4 = 25%....then 7 x $14.50...plus 30 mins at $14.50/hr...remember 30 mins is 1/2 an hour so whats $14.50 divided by two..?...now add it all up and theres you answer...!
*May 31, 2012*

**Art**

Spanish Romanticism...not sure about any other....its oil on canvas (1820)
*May 30, 2012*

**math**

11,,,,,,!!!!
*May 29, 2012*

**math**

3y-12=21
*May 29, 2012*

**math**

It says Complete 10/3 on maths homework...what does this mean...thanks.. :)
*May 29, 2012*

**chemistry**

Its c....K= potassium...and there is is only one mentioned...and Cl= chlorine...again only one mentioned.. So its C...look up your elements table and it will tell you what K..is etc...then you wont have to send as many questions in...!!
*May 28, 2012*

**chemistry**

Its D..!!...the 2 after the Br means its attached to that element..so read as 2 X Br....there is nothing after the Mg...so that means there ais only one So therefore its D...
*May 28, 2012*

**Minoxidil**

C9H15N2O...chemical formula
*May 28, 2012*

**Minoxidil**

Try under its more common name "Rogaine"...its basically a chemical that slows hair loss....
*May 28, 2012*

**Religion**

Its Islam = Peace
*May 28, 2012*

**Physics**

A convex lens forms a real image 6 times the size of the object. The distance between object and image is 33 cm. Find the focal length of the lens.
*May 28, 2012*

**physics**

An object is placed 75.0 cm from a screen. (a)Where should a converging lens of focal length 8.0 cm be placed to form an image on the screen? shorter distance __cm from the screen farther distance __cm from the screen (b)Find the magnification of the lens. magnification if ...
*May 23, 2012*

**Chemistry**

Find [H+] [OH-] and Ph
*May 21, 2012*

**Chemistry**

A solution is prepared by adding 47.3 mL of concentrated hydrochloric acid and 16.3 mL of concentrated nitric acid to 300 mL of water. More water is added until the final volume is 1.00 L. Calculate [H+], [OH -], and the pH for this solution. [Hint: Concentrated HCl is 38% HCl...
*May 21, 2012*

**physics**

Calculate the magnitude and direction of the Coulomb force on each of the three charges connected in series: 1st - 6 micro Coulombs (positive charge) 2nd - 1.5 micro Coulombs (positive charge) 3dr - 2 micro Coulombs (negative charge) Distance between 1st and 2nd - 3cm Distance...
*May 21, 2012*

**physics**

An object is placed 75.0 cm from a screen. a)Where should a converging lens of focal length 8.0 cm be placed to form an image on the screen? shorter distance __cm from the screen farther distance __cm from the screen b)Find the magnification of the lens. magnification if ...
*May 21, 2012*

**physics**

A wire of initial length L0 and radius r0 has a measured resistance of 2.5 . The wire is drawn under tensile stress to a new uniform radius of r = 0.45r0. What is the new resistance of the wire?
*May 21, 2012*

**physics**

An air-filled capacitor consists of two parallel plates, each with an area of 7.60 cm2, separated by a distance of 1.70 mm. If a 19.2-V potential difference is applied to these plates, calculate the following: (a) the electric field between the plates, magnitude (in kV/m) and ...
*May 18, 2012*

**physics**

The potential difference between the accelerating plates of a TV set is about 30 kV. If the distance between the plates is 1.1 cm, find the magnitude of the uniform electric field in the region between the plates. (in N/C)
*May 17, 2012*

**physics**

Calculate the magnitude and direction of the Coulomb force on each of the three charges connected in series: 1st - 6 micro Coulombs (positive charge) 2nd - 1.5 micro Coulombs (positive charge) 3dr - 2 micro Coulombs (negative charge) Distance between 1st and 2nd - 3cm Distance...
*May 16, 2012*

**Chemistry **

Consider the following reaction: 2NOCl(g) 2NO(g) + Cl2(g) Initially pure NOCl(g) is placed in a vessel at 3.00 atm. At equilibrium, 0.416% of the NOCl has decomposed. Determine the value for Kp.
*May 13, 2012*

**Chemistry**

For the reaction below, Kp = 1.16 at 800.°C. CaCO3(s) CaO(s) + CO2(g) If a 25.0-g sample of CaCO3 is put into a 10.2-L container and heated to 800.°C, what percent of the CaCO3 will react to reach equilibrium?
*May 12, 2012*

**Science**

Table salt has a solubility of 36 g of salt in 100 g of water at 40°C. If 15 g of the salt are added to 50 g of water at the same temperature, is the resulting solution saturated or unsaturated? Explain your answer
*May 11, 2012*

**Math**

The question asks the opposite... not yellow. so 9/12 * 10/15 = .75 * .666 = 50%
*May 9, 2012*

**Physics**

calculate change in the momentum. remember that after it experiences this "perfectly elastic collision" it has a negative velocity. Therefore the change in momentum would be p = abs|m1v1 + m2v2| change in momentum p = Ft Force would be the average force or in this ...
*May 9, 2012*

**Chemistry**

solve q initial for the 240g of coke/water. solve q initial for the ice. subract q ice from q coke, then solve for deltaT q(coke) - q(ice) = (4.18 J/gK)(285g)(deltaT)
*May 9, 2012*

**?**

brought
*May 8, 2012*

**chemistry**

4Na + 02 = 2Na2O Considering Na is the limiting reagent.. 1.15g Na x 1molNa/23g x 2molNa2O/4molNa x 1molNa2O/62g = grams of Na2O
*May 8, 2012*

**Environmental Chemistry**

This is a strong acid/base titration. Balance your equation for the reaction and calculate if you have excess H30+ or OH- Remember that pH=-log[H30+] and pOH = -log[OH-] pOH = 14 - pH Where [H30+] and [OH-] is the concentration of each substance in moles/liter
*May 8, 2012*

**physics**

0 J
*May 7, 2012*

**math**

A dodecagon is the term for a regular 12 sided polygon with equivalent angles and side lengths. Looks like most the other regular 2D polygons. If its irregular.. use your imagination
*May 7, 2012*

**physcis**

1. Fnet=ma=Fs Fnet=ma=usFn Fnet=ma=usmg mass cancels a=usg Please stop reposting your question
*May 7, 2012*

**physics**

No energy will be required, as no work is being done one the weight as it is carried across the room. Wnc = Fdcos90 cos90 = 0 Wnc = 0 Wnc = change in Emech change in Emech = 0
*May 7, 2012*

**physics**

1. Fnet=ma=Fs Fnet=ma=usFn Fnet=ma=usmg mass canceles a=usg 2. not a very good visual description, cant figure out what you mean. draw pictures. use a free body diagram
*May 7, 2012*

**Chemistry**

DxDp = h/4p Where Dx is uncertainty of position, Dp is uncertainty in momentum, h is Planck's constant 5.26e-33 Joule seconds, and p is linear momentum, P = mv.
*May 7, 2012*

**physics**

A potential difference of 102 mV exists between the inner and outer surfaces of a cell membrane. The inner surface is negative relative to the outer surface. How much work is required to eject a positive sodium ion (Na+) from the interior of the cell? (in J)
*May 7, 2012*

**physics**

An electron is accelerated by a constant electric field of magnitude 325 N/C. (a) Find the acceleration of the electron. (m/s^2) (b) Use the equations of motion with constant acceleration to find the electron's speed after 1.05 10-8 s, assuming it starts from rest. (m/s)
*May 6, 2012*

**Accouting**

How much investment per dollar of expected annual operating savings can a company afford if the investment has an expected life of 8 years and its required rate of return is 14%?
*May 5, 2012*

**physics**

A 8.01-nC charge is located 1.95 m from a 4.06-nC point charge. (a) Find the magnitude of the electrostatic force that one charge exerts on the other. (b) Is the force attractive or repulsive?
*May 5, 2012*

**physics**

Two loudspeakers are placed above and below each other and driven by the same source at a frequency of 3.70 102 Hz.An observer is in front of the speakers at point O, at the same distance from each speaker. What minimum vertical distance upward should the top speaker be moved ...
*May 3, 2012*

**physics**

Tension is maintained in a string. The observed wave speed is 21 m/s when the suspended mass is 3.0 kg. a) What is the mass per unit length of the string? (in kg/m) b) What is the wave speed when the suspended mass is 1.6 kg? (in m/s)
*May 2, 2012*

**Marketing**

I need help coming up with 3 realistic Objectives for NIKE SHOES that would be used on a marketing plan. The objectives needs to be Specific, Measurable, Attainable, Realistic and Time Sensitive.
*April 30, 2012*

**Calculus**

Use the form of the definition of the integral to evaluate the intergral. From 0 to 9 (10+6x-x^2)
*April 20, 2012*

**Physics (Energy and Momentum)**

solved
*April 17, 2012*

**Physics (Energy and Momentum)**

A block of mass m1 = 1.00 kg slides along a frictionless table with a speed of 16.0 m/s. Directly in front of it, and moving in the same direction, is a block of mass m2 = 6.00 kg moving at 8.00 m/s. A massless spring with a spring constant k = 1320 N/m is attached to the ...
*April 17, 2012*

**Physics (Energy and Momentum)**

solved using thrust = v (dM/dt)
*April 17, 2012*

**Physics (Energy and Momentum)**

A 4400 kg rocket is set for vertical firing. If the exhaust speed is 1500 m/s, at what rate (in kilograms/second) must the gas be ejected to supply the thrust needed to give the rocket an initial upward acceleration of 23.0 m/s^2? Not sure where to start.
*April 17, 2012*

**Physics (Energy and Momentum)**

A body of 5.10 kg mass makes an elastic collision with another body at rest and continues to move in the original direction, but with one-fourth of its original speed. What is the mass (in kilograms) of the struck body? Assuming a perfectly elastic collision, KEi=KEf ive tried...
*April 16, 2012*

**Physics Mechanics (unsolved)**

An electron of mass 9.1E-31 kg is released from rest at a distance of 7.1 E-10 m from a fixed electron. The force on the movable electron is given by the function F = 2.3E-28/r^2, where r is the distance between the electrons. Find the maximum velocity (in meters/second) of ...
*April 13, 2012*

**Physics (Mechanics) - unanswered**

An electron of mass 9.1E-31 kg is released from rest at a distance of 7.1 E-10 m from a fixed electron. The force on the movable electron is given by the function F = 2.3E-28/r^2, where r is the distance between the electrons. Find the maximum velocity (in meters/second) of ...
*April 13, 2012*

**Physics (Mechanics)**

An electron of mass 9.1E-31 kg is released from rest at a distance of 7.1 E-10 m from a fixed electron. The force on the movable electron is given by the function F = 2.3E-28/r^2, where r is the distance between the electrons. Find the maximum velocity (in meters/second) of ...
*April 12, 2012*

**physics (mechanics)**

A running man has half the kinetic energy of a boy half his mass. The man speeds up by 1.30 m/s and then has the same kinetic energy as the boy. What is the speed (in meters/second) of the boy?
*April 12, 2012*

**Math 1200**

a complex has 205 apartment units. When the rent is $635 per month all 205 units are occupied.Assume that for each $75 increase in rent 15 units becomes vacent. Assume that the number of occupied units is a linear function of the rent. Each occupied unit also requires an ...
*April 5, 2012*

**Math**

Jim has 400 ft of fence material and needs to enclose an area of 10,000 square feet for his garden as the diagram depicts. (The length of the house is 62 ft and the fence extends the same distance on either side of the house.) What must the dimensions of the rectangular ...
*March 27, 2012*

**Physics**

In the dangerous "sport" of bungee-jumping, a daring student jumps from a balloon with a specially designed elastic cord attached to his waist, as shown in Figure P5.77. The unstretched length of the cord is 25.0 m, the student weighs 675 N, and the balloon is 36.0 m...
*March 25, 2012*

**Math**

in a group of 30 students,20 are male,15 are from southern region,9 from the central and 6 from the north.if the proportion of female students is the same for each region,how many students are either female or from the central{or both}A.9 B.10 C14 D.16 E.19
*March 23, 2012*

**Maths**

Taona and Stella both live 5km from the Hospital,stella walks at a speed of 4km/hr,while taona cycles.if stella leaves home 45minutes earlier than Taona,they arrive at the same time.how fast does Taona cycle
*March 20, 2012*

**Maths**

A shopkeeper sells a hat for $14.the amount he gains is three times the amount he loses when he tries to sell it for $8.find the cost price? A.9 B.8.5 C.9.5 D.11 E.10
*March 20, 2012*

**Maths**

A steel bar 3.6m long is in the form of a triangular prism.its section is right angled i sosceles triangle with sides 50mm.the volume of the bar in cubic meters is? A.0.045 B.0.0045 C.0.0125 D.0.018 E.0.00125
*March 20, 2012*

**Math**

A product costs k100,90% of the price being production cost,the remainder being tax.if the government raises the tax by 50%,by how much in % will the factory have to reduce its production cost,to keep the price still at k100? A.5 B.85/90 C.50/9 D.85/15 E.15
*March 19, 2012*

**Chemistry**

I keep getting the equation wrong!
*March 14, 2012*

**chemistry**

I had similar problem, except correct choices were 2A(g)+B(s)->3C(g) and A(g)+B(g)->3C. Just wanted to thank Dr.Bob for explaining how it actually works.
*March 14, 2012*

**4th grade math**

Go to google Type in 5/6*288. "Of" means to multiply 5/6*288=240
*March 12, 2012*

**algebra**

you just distribute across. 1/4 = .25 .25(n+5) = .25n + .25(5) = .25n +1 = 1/4n + 1
*March 12, 2012*

**Physics (dynamics)**

A 47.0 kg slab rests on a frictionless floor. A 18.0 kg block rests on top of the slab. The static coefficient of friction between the block and the slab is 0.50, while the kinetic coefficient of friction is 0.40. The top block is acted upon by a force of 120 N. What is the ...
*March 10, 2012*

**Chemistry**

If Kc = 0.480 at 40.°C and Kc = 0.630 at 90.°C, what is ΔH° for the reaction? X<---->Y
*March 10, 2012*

**tax**

For the current year, Sheila Jones had adjusted gross income of $100,000. During the year, she contributed $6,000 to her church and an additional $3,000 to qualified charities. She also contributed religious artwork with a fair market value of $60,000 and a basis of $20,000 to...
*March 8, 2012*

**tax**

Under a court-ordered decree of separate maintenance executed in 2011, Rebecca is required to pay her ex-husband, Carl, $5,000 a month until their youngest son turns age 18. At that time, the required payments are reduced to $2,500 per month. How much of each payment is ...
*March 8, 2012*

**Accounting**

For the current year, Sheila Jones had adjusted gross income of $100,000. During the year, she contributed $6,000 to her church and an additional $3,000 to qualified charities. She also contributed religious artwork with a fair market value of $60,000 and a basis of $20,000 to...
*March 8, 2012*

**Accounting**

Which of the following expenses is deductible, but subject to the 2% limitation on Form 1040, Schedule A; Job Expenses and Most Other Miscellaneous Itemized Deductions? A. A blue suit for an accountant b. Uniforms for a UPS delivery person c. The cost of hauling tools to work ...
*March 8, 2012*

**Calculus**

Find the local linearization of f(x) near x=0 and use it to approximate the value of a. f(x)=sqrt((b^2)+x) a=sqrt(26)
*March 8, 2012*

**Calculus**

Glenview Community College wants to build a rectangular parking lot on land bordered on one side by a highway. It has 380 feet of fencing to use on the other three sides. What should be the dimensions of the lot if the enclosed area is to be a maximum?
*March 8, 2012*

**physics **

The figure shows a golf ball passing through a windmill at a miniature golf course. The windmill has 8 blades and rotates at an angular speed of 2.02 rad/s. The opening between successive blades is equal to the width of a blade. A golf ball of diameter 3.27 x 10-2 m is just ...
*March 8, 2012*

**tax**

during 2011 sam paid following: property tax on residence (paid from escrow account) $1550 Property tax portion of car registration (based on value) $400 property taxes on land held for long term appreciation $350 What amount can Sam deduct as property taxes in calculating his...
*March 7, 2012*

**Maths**

increasing orignal price of an article by 15% and then increasing the new price by 15% again is equivalent to increasing the orignal price by what %?
*March 6, 2012*

**chemistry**

what is the answer?
*February 29, 2012*

**math**

Cierra arrived at her dance at 9:05. She waited in the classroom for 10 minutes and them the class began. If the class ended 1 hour 10 minutes later,at what time did the class end? A.10:15 B.10:20 C.10:25 D.10:30 C?
*February 23, 2012*

**math**

The table shows the total number of emails that the Wright family received this morning. Mr.Wright 7 emails Mrs.Wright 8 emails Cole 3 emails Trinity 3 emails If the family receives 7 more emails,which is the most reasonable prediction of the number of emails that will go to ...
*February 23, 2012*

**Economics**

Consider an economy with the following aggregate demand(AD) and aggregate supply(AS) schedules. These schedules reflect the fact that, prior to the period we're examining, decisions makers entered into contracts and made choices anticipating that the price level would be ...
*February 22, 2012*

**Economics**

Consider an economy with the following aggregate demand(AD) and aggregate supply(AS) schedules. These schedules reflect the fact that, prior to the period we're examining, decisions makers entered into contracts and made choices anticipating that the price level would be ...
*February 22, 2012*

**Chem**

What about the second part? plz and thank you
*February 21, 2012*

**Chem**

In reverse osmosis, water flows out of a salt solution until the osmotic pressure of the solution equals the applied pressure. If a pressure of 41.0 bar is applied to seawater, what will be the final concentration of the seawater at 20 °C when reverse osmosis stops? ...
*February 21, 2012*

**Science**

Are all solutions mixtures? Are all mixtures solutions? Explain with examples. I put all solutions are mixtures but all mixtures aren't solutions. I don't know how to explain it with examples
*February 21, 2012*

**Math**

The graph shows the number of airplanes that flew out of an airport last week Mon=4airplanes Tues=7airplanes Wed=3airplanes Thu=8airplanes Fri=5airplanes If each airplane carried 120 people then how many people flew out of the airport last week? A.3240 B.3140 C.1080 D.880 B?
*February 21, 2012*

**algebra**

write an absolute value inequality describing the minutes of data (w) a full dvd will hold if a typical dvd can store between 137.9 and 142.1 minutes of data before it is considered full
*February 20, 2012*

**math**

Thanks Cheryl :-)
*February 18, 2012*

**math**

In a sports league of n teams in which each team plays every other team twice, the total number N of games to be played is given by N = n2 - n. What is the total number of games to be played in a football league having 17 teams?
*February 18, 2012*

**chemistry**

Pb(OH)2 (s) + 2NaOH (aq) <--> [Pb(OH)4]^2- + 2Na^+ (aq) Don't include the "-" in NaOH
*February 13, 2012*

**Math**

Adam has $300 when he entered the store. He spent $72 on some CD's. He wants to use the rest of the money to buy some DVD's. If DVD's cost $18 each, which would be the best way for Adam to find how many DVD's he can afford to buy? A.Multiply 18 by 72 B.Add 300 ...
*February 8, 2012*

**Math**

I mean 6 for 2
*February 8, 2012*

**Math**

Nathan can purchase 5 lemons for $2. Which is one way to find the number of lemons Nathan can buy with $20? A.add 6 and 2 and then multiply the sum by 20 B.add 2 and 20 and then multiply the sum by 6 C.divide 6 by 2 and then add the quotient to 20 D.divide 20 by 2 and then ...
*February 8, 2012*

**physics**

A 790kg boulder is raised from a quarry 188m deep by a long uniform chain having a mass of 600kg . This chain is of uniform strength, but at any point it can support a maximum tension no greater than 3.00 times its weight without breaking.
*February 8, 2012*

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