Sunday

April 20, 2014

April 20, 2014

Number of results: 1,149

**Pre Calculus**

Exponential growth and decay find the half life of a radioactive substance if 220 grams of the substance decays to 200 grams in 4 years?
*Tuesday, October 25, 2011 at 1:40am by Josh*

**Science- Earth and its History**

What can scientists learn from the rate at which radioactive elements decay? A. a rock's absolute age* B. the relative age of rock layers C. where one soil horizon ends and the next begins D. the difference between molds and casts. After six half-lives, what percentage of a ...
*Tuesday, October 15, 2013 at 3:18pm by Anonymous*

**ms sue help**

can u check my answer and check my answer on another? 4. _____ is measured in half-lives. *Radioactive decay Absolute age Uniformitarianism Carbon-14 I thinks its a
*Tuesday, November 20, 2012 at 1:16pm by Jman*

**ap calculus**

suppose that the amount in grams of a radioactive substance present at time t (in years) is given by A (t) = 160e-.70t. Find the rate of decay of the quantity present at the time when t = 4
*Sunday, December 2, 2012 at 9:07pm by steve b*

**Chemistry**

I'm not exactly sure of your confusion. Elements that are above the band of stability (too many neutrons) generally emit beta particles. C14 is in the category. Be 13 is a radioactive isotope of the usual Be we see and of course it has a neutron:proton ratio that is too high ...
*Thursday, October 16, 2008 at 4:55pm by DrBob222*

**12th grade**

The radioactive isotope of Carcon (^14C)has a half life of 5730. What is the decay constant of ^14C? If we start with a sample of 1000 carcon nuclei, how many will be left in 22920 years time?
*Thursday, April 8, 2010 at 12:34pm by Moe*

**Pre-Cal**

The radioactive isotope of Carcon (^14C)has a half life of 5730. What is the decay constant of ^14C? If we start with a sample of 1000 carcon nuclei, how many will be left in 22920 years time?
*Thursday, April 8, 2010 at 1:43pm by Moe*

**chemistry -- radioactive decay**

k = 0.693/t1/2 Solve for k. ln(No/N) = kt No = 150 N = solve for this k from above. t = hours for t and solve for N in grams.
*Tuesday, September 18, 2012 at 11:53pm by DrBob222*

**science**

radioactive decay occurs when atoms a) lose mass b) join with atoms of another element c) break down to form atoms of another element d) are exposes to chemical weather
*Friday, December 13, 2013 at 12:08pm by victoria*

** physic**

They are man-made radioisotopes of heavy elements that are not part of the natural radioactive decay series that start with uranium or thorium. In other words, they only found on Earth if they were created in an accelerator, nuclear explosion, or nuclear reactor.
*Tuesday, March 9, 2010 at 6:50am by drwls*

**Chemistry please check**

1. All of the naturally occurring radioactive decay series end when the radioactive elements have decayed to bismuth (Bi) hydrogen (H) lead (Pb) uranium (U) answer: Uranium (U) 2. This type of radiation can easily pass through a human. gamma ultra-violet beta alpha answer: ...
*Friday, February 15, 2008 at 11:35pm by Mary*

**chemistry**

Rates of chemical reactions usually depend on temperature and pressure. However, half-life of all radioactive elements is independent of both T and p. How can these decay rates be independent of T if we beleive in the Arrhenius equation?
*Tuesday, July 27, 2010 at 8:56pm by Jin*

**Physical Science**

3. Radioactive decay of nuclei often involves several decays before a stable nucleus is formed. This is called a decay chain. What stable isotope is formed when radon-222 undergoes a decay chain of four alpha decays followed by four beta decays? (A) tungsten-206 (B) platinum-...
*Wednesday, November 20, 2013 at 6:28pm by Adam*

**Chemistry**

Each of the following nuclides is known to undergo radioactive decay by production of a beta particle, ^0_-1e. Write a balanced nuclear equation for each process. (Use 'e' for an electron, 'p' for a positron, and 'n' for a neutron. Omit states-of-matter from your answer.) a...
*Saturday, November 27, 2010 at 3:54pm by Jane*

**Chemistry**

The half-life for radioactive decay of 14C is 5730 years (it emits β-particles with energy of 0.16 MeV). An archaeological sample contained wood that had only 72% of the 14C found in living trees. What is its age?
*Thursday, April 8, 2010 at 4:02pm by Zoa*

**Physics**

A half-life is how long it takes for a radioactive isotope to decay by half. At 2 PM, you will have .5 grams of the material. Each hour thereafter, divide the material by half to see how much remains.
*Saturday, November 17, 2007 at 12:41pm by Michael*

**college**

a certain radioactive isotope has a half life or 850 years.how many years would it take for a given amount of this isotope to decay to 70% of that amount?
*Thursday, December 2, 2010 at 9:53am by Kiesha*

**chemistry**

The half-life for the radioactive decay of calcium-47 is 4.5 days.If a sample has an activity of 4.00uCi after 13.5 days, what was the initial activity of the sample?
*Wednesday, September 26, 2012 at 2:30pm by Shay*

**physis**

Search: 2. Explain how radioactive decay has always warmed the Earth from the inside, and nuclear fusion has always warmed Earth from the outside.
*Sunday, January 26, 2014 at 10:50pm by barbara*

**Physics**

Can someone give me an example of how to use this formula: 15.Obtain three half-life (T0.5) times from the graph. Average them.(T0.5)av. Or is there a web site i can go to that shows all steps to using pennies for radioactive decay experiment? .
*Thursday, November 15, 2007 at 1:25pm by Will*

**physics ASAP**

Can someone give me an example of how to use this formula: Obtain three half-life (T0.5) times from the graph. Average them.(T0.5)av. Or is there a web site i can go to that shows all steps to using pennies for radioactive decay experiment? .
*Sunday, November 18, 2007 at 2:45pm by Will*

**geology / science**

the age of granite can be determind using radiometric dating, explain the basis for the determination of a 238 U- Pb radiometric date of 1120 Ma for a granite. I have as the answer 238 U decays to Pb with an experimental law, that is the amount of U and Pb in granite are ...
*Wednesday, April 18, 2007 at 10:16am by bex*

**Science**

Do you mean fluorescence of bright visible light when illuminated by invisible ultraviolet light? Fluorescence is a property of some chemical compounds, not just elements. Radium (an element) glows because of radioactive decay that is always taking place. So does tritium, an ...
*Wednesday, May 12, 2010 at 8:38pm by drwls*

**chem**

Radioactive substances decay by first-order kinetics. How many years would be required for a sample containing strontium-90 to decrease to 58.32% of its initial activity? The half-life of strontium-90 is 2.88e1 years.
*Saturday, February 22, 2014 at 6:36pm by sara*

**AP Environmental Science (URGENT)**

Strontium-90 is a radioactive waste product from nuclear reactors. It has a half-life of 29 years. How many years will it take for a quantity of strontium-90 to decay to 1/16 (one-sixteenth) of its original mass?
*Wednesday, January 11, 2012 at 9:07pm by Heather*

**Physics**

The slow radioactive decay of elements like Uranium that are still present in the earths crust generates heat from within. The fusion of hydrogen into helium in the sun, through a series of steps that also involve carbon and oxygen transmutation, provides the energy that keeps...
*Friday, April 25, 2008 at 11:35pm by drwls in Sloveina*

**Chemistry**

The first is the fact that all nuclear decay reactions are first order. That tells you that you can use the ln(No/N) = kt equation and that k = 0.693/t1/2. Other orders have different equations for t1/2 and for time for x amount to decay. In kinetics it makes little difference...
*Friday, April 27, 2012 at 9:00pm by DrBob222*

**Science**

Natural Uranium contains 15 percent Sm147. Sm147 is radioactive and decays by alpha decay. What will be the number of disintegrations per gram per second of the natural element? The half-life of Sm147 is 1.3x1010 years.
*Sunday, September 30, 2012 at 3:51am by Nivia*

**chemistry**

I really don't know how to answer this question because H, the fist element in the periodic table, has a radioactive isotope. Also, carbon, near the beginning, and Po, Ra, U, and a host of others at the end of the table are radioactive naturally. There are some naturally ...
*Monday, June 2, 2008 at 7:55pm by DrBob222*

**chemistry(?)**

How are you defining k? Are you taking the ln of [R] or of [R(t)]/R(0)] ? Is [R] the concentration of a reactant? This looks like an equation for first-order chemical decomposition or radioactive decay. If [R(t)] = [Ro]e^-kt, then ln{[R(t)]/R(0)]} = -kt If -kt = -0.0237 when t...
*Thursday, March 8, 2012 at 10:13pm by drwls*

**calculus**

A sample of a radioactive substance decayed to 94.5% of its original amount after a year. (Round your answers to two decimal places.) (a) What is the half-life of the substance? (b) How long would it take the sample to decay to 65% of its original amount?
*Friday, November 9, 2012 at 6:00pm by kela*

**Physics**

Is a small or large decay constant best for protection against gamma radiation? Hint: Calculate half thickness. Example: Decay constants for Pb, Al, water, and Fe are 0.77, 0.16, 107, and 0.44. Which is better for radiation shielding? The larger the decay constant, the fewer ...
*Monday, April 30, 2007 at 5:26pm by Caleb*

**Chemistry**

ALL radioactive decay problems are first order so you use ln(No/N) = kt. If you want the half life in hours, leave it as is. If you want it in min or seconds, then convert the 24 hours to some other unit. Since the problem doesn't specify, I would leave it as 24 hours.
*Thursday, February 23, 2012 at 2:44pm by DrBob222*

**chem**

Nuclide X has decay constant 1.08 h-1. It can decay in 2 branches, to nuclide Y or to nuclide Z: X --> Y, with decay constant 0.43 h-1, and X --> Z, with unknown decay constant. If there are 10 moles of nuclide X at time t = 0, how many moles of each daughter will there ...
*Monday, October 21, 2013 at 7:10pm by Jane*

**chemistry**

the longest lived radioactive isotope yet discovered is the beta-emitter tellurium-130.it has been determinded that it would take 2.4 x 10^21 years for 99.9% of this isotope to decay. write the equation for this reaction, and identify the isotope into which tellurium-130 decays.
*Monday, July 12, 2010 at 1:03pm by penelope*

**Science**

If a radioactive isotope has half life of 5 days,how long will it take for its radioactive strength to be a maximum of one thousandth,(1/1000) of its original value?
*Tuesday, December 21, 2010 at 6:59pm by Bree*

**engineering **

It depends upon the angular distribution of the emitted particles. If you are talking about radioactive decay, unless the nuclei are aligned (which is extremely unlikely) the emission will be isotropic, i.e, the same in all directionns. The flux (emission per area) 30 cm away ...
*Thursday, January 13, 2011 at 10:53am by drwls*

**Physics**

This is related to the classic thought experiment "Schroedinger's cat". Your answer seems intuitively correct, but in quantum mechanics, until a decay measurement is actually made, the radioactive source exists in a mixed quantum state, with nonzero probability that each ...
*Monday, March 31, 2008 at 4:04am by drwls*

**Chemistry**

The half-life of phosphorus-32 is 14.26 days. The decay constant is k=4.86×10−2/days. If you accidentally spill phosphorus-32 onto your shoe, how long would it take before 99.9% of the radioactive material has decayed so that you can safely wear the shoes again?
*Sunday, May 1, 2011 at 2:08pm by Anonymous*

**chemistry**

a radioactive material is undergoin nuclear decay. After 40 minutes, 25% of the sample remains. What is the half life of the sample? Pls say the formula how to calculate it a)10 mins b) 20 mins c) 40 mins d)80 mins e) 160 mins
*Monday, May 28, 2012 at 10:38am by star*

**Chemistry**

Write a nuclear equation for the following: Iodine 131 undergoes beta decay two times Plutonium 239 is an alpha emitter Th 234 undergoes beta decay once and then alpha decay How do I go about writing nuclear equations?
*Monday, December 6, 2010 at 1:46pm by Jake*

**MATH help**

a certain radioactive isotope has a half life of approx 1,300 years . How many years to the nearest year would be required for a given amount of this isotope to decay to 55% of that amount. So I am not sure where to put the 1,300 1,300=2600*e^t or A=x*e^1300
*Monday, September 26, 2011 at 1:19pm by HM*

**MATH help**

a certain radioactive isotope has a half life of approx 1,300 years . How many years to the nearest year would be required for a given amount of this isotope to decay to 55% of that amount. So I am not sure where to put the 1,300 1,300=2600*e^t or A=x*e^1300
*Monday, September 26, 2011 at 1:51pm by HM*

**Math**

a certain radioactive isotope has a half life of approx 1,300 years . How many years to the nearest year would be required for a given amount of this isotope to decay to 55% of that amount. So I am not sure where to put the 1,300 1,300=2600*e^t or A=x*e^1300
*Tuesday, September 27, 2011 at 1:38am by HM*

**MATH help**

a certain radioactive isotope has a half life of approx 1,300 years . How many years to the nearest year would be required for a given amount of this isotope to decay to 55% of that amount. So I am not sure where to put the 1,300 1,300=2600*e^t or A=x*e^1300
*Tuesday, September 27, 2011 at 10:20am by HM*

**Math with science**

Radioactive iodine treatment is so successful at treating hyperthyroidism that it has virtually replaced thyroid surgery. To the nearest full day, determine how long it will take for 400 millicuries of I-131, which has a half-life of 8 days, to decay to 3.125 millicuries. 56 ...
*Sunday, July 27, 2008 at 12:39pm by Liz*

**Calc**

A sample of a radioactive substance decayed to 93.5% of its original amount after a year. a) What is the half-life of the substance? ? years (b) How long would it take the sample to decay to 10% of its original amount? ? years
*Sunday, November 8, 2009 at 7:47pm by Lee*

**Linear Algebra**

whats the exponential decay equation for 100 atoms that decay 1/20 per day
*Thursday, January 12, 2012 at 10:22pm by Anonymous*

**chemistry**

The question I am having trouble with is: Scientists originally were uncertain whether the oxygen gas produced during photosynthesis came from CO2, H2O, or from both. How could radioisotope tracers be used to settle that question? Chemistry - DrBob222 6CO2 + 6H2O ==> ...
*Monday, April 15, 2013 at 12:04am by Madison*

**chemistry**

1). half life = ln(2) / lambda where lambda is the radioactive decay constant 2). A(t) = 12mCi * e ^ - (lambda * t) where t is time, A(t) is activity as a function of time 15 hr = ln2 / lambda solve for lambda convert 2.5 days to hours Then t = 2.5 days * (24 hrs / day) Plug ...
*Thursday, October 4, 2012 at 2:43pm by Jennifer*

**Math**

the symbol ^ means "raise to". the symbol * means "multiplied by" as in for example 3^2 = 3*3 = 9 Yes, we're looking for the half-life. Half-life is the time it takes for a substance to achieve 1/2 of its original amount when it undergoes radioactive decay. the formula used ...
*Tuesday, August 20, 2013 at 9:23am by Eren Jaeger*

**Biology**

Help please! Do organic fertilizer products (in bags or sacks) decay after some time? If yes, how long will it take to decay?
*Thursday, March 8, 2012 at 10:06pm by Namie*

**Pre Calc**

The half-Life of radioactive earthium is 2651 years. Find how many years it will take 100 grams of earthium to decay to 10 grams. I know the equation is A=Ae^(-rt) I tried working it out but I think I am doing it wrong. I did 10=100e^(-r*2651) Can anyone help? Thanks a lot
*Thursday, January 13, 2011 at 11:22pm by Alex*

**Science**

Under which of the following conditions would a fossil most likely form? a. a living thing dies and sediment is very slowly deposited on top of its body b. a living thing dies and sediment quickly covers its body* c. a living thing dies and its skeleton is left exposed to the ...
*Wednesday, October 30, 2013 at 8:57pm by Anonymous*

**College Physics II**

A typical gamma ray emitted from a nucleus during radioactive decay may have an energy of 736 keV. What is its wavelength? A microwave oven produces electromagnetic radiation at λ = 12.1 cm and produces a power of 778 W. Calculate the number of microwave photons produced ...
*Thursday, November 25, 2010 at 11:33am by VJC*

**science - biology**

A photosynthesis experiment uses Chlorella to track the route taken by 14C in photosynthesis. The 14C is provided from CO2 and no new sources of CO2 are available. After the experiment the scientist extracts all of the starch produced and analyses the Carbon present. She ...
*Saturday, May 7, 2011 at 8:57am by jack*

**Science**

Here is a site that talks in general terms about decay. Scroll down to the menu, see #4, types of decay, click on that for particulars.
*Friday, April 24, 2009 at 1:29pm by DrBob222*

**Algebra 2 Decay **

You have 20 grams of phosphorus-32 that decays 5% per day. How long will it take for hlaf of the original amount to decay?
*Friday, February 17, 2012 at 1:03am by Peter*

**Algebra 2 Decay**

I looked up the half life of P-32. It is 14.28 days. I suspect 5% decay in the problem is just a close number.
*Friday, February 17, 2012 at 1:03am by DrBob222*

**Science**

If a radioactive isotope has half life of 5 days,how long will it take for its radioactive strength to be a maximum of one thousandth,(1/1000) of its original value? Can anyone give me a VERY SIMPLE explanation of this please? Thank you.
*Saturday, January 29, 2011 at 9:31pm by Korina*

**ChemB**

measurements of carbon 14 taken from linen wrappings of the book of isaiah from the dead sea scrolls indicate that the scrolls contain 79.5% of the carbon 14 expected in living tissue. how old are these scrolls if the half life of carbon 14 is 5730 years? All radioactive decay...
*Sunday, January 22, 2012 at 9:28pm by L.Bianchessi*

**Science-3 questions.**

Which of the following best describes the climates of Europe and North America during the 1.8 million years of the Quaternary period? hot and dry cool and rainy periods followed by droughts warm and mild a series of ice ages followed by periods when the glaciers melted Which ...
*Wednesday, December 11, 2013 at 3:55pm by Princess Anna*

**biology**

14 points Save A photosynthesis experiment uses Chlorella to track the route taken by 14C in photosynthesis. The 14C is provided from CO2 and no new sources of CO2 are available. After the experiment the scientist extracts all of the starch produced and analyses the Carbon ...
*Saturday, May 7, 2011 at 9:01am by jack*

**chemistry**

I'm not sure what you mean by stable; however, I thought all of them were stable at 0 C except for Rn which is radioactive. Some of the others have radioactive isotopes.
*Tuesday, February 23, 2010 at 3:53pm by DrBob222*

**Chemistry**

If a 100.0 gram sample of a radioactive isotope goes through three half-lives, how much of the original radioactive isotope will remain?
*Thursday, January 24, 2013 at 9:17pm by OhSnap*

**chemistry**

If the radiicativr decay of nuclear explosion contains 90 Sr , with a half life of 28.1 years how long will it take for 99 of this radioaioot to decay
*Monday, December 5, 2011 at 7:38pm by devin*

**chemistry**

if you start with 100mg of radioactive material that has a half life of one hour, how many mg's of radioactive material would you have in 10.2284952 hours?
*Tuesday, February 1, 2011 at 2:12pm by carlos*

**Math Growth & Decay**

a) A growth factor of 1.22 corresponds to a rate of? b)a growth rate of 6.7% corresponds to a growth factor of? c)a decay factor pf 0.972 corresponds to a decay rate of? d)A decay rate of 12.3% corresponds to a decay factor of?
*Wednesday, May 15, 2013 at 1:05am by kim*

**PHYS**

Help! Initially there are 6x10^9 radioactive of element W (decay constant 0.173/day) in a sample. As a nucleus of W decays, it converts 2.67x10^-28 kg of its mass to energy and releases the energy. How much time (in days) is required for the sample to releae a total of 7.2x10...
*Monday, April 25, 2011 at 4:46pm by Jenn*

**Concentration and Reaction**

The rate of the following reaction: Radioactive decay of 90Sr, is characterized by the rate constant k = 0.024 year-1. What is the half-life (in years) for this reaction at the same conditions when the initial concentrations are 0.0356 M? (Round your answer to 3 significant ...
*Saturday, November 20, 2010 at 10:36pm by Confused*

**Calculus-derivatives**

Verify if these are correct answers. 1. The derivative of f(x)=e^2x -e^-2x is f'(x)=2e^2x - 2e^-2x? 2.A certain radioactive substance is decaying so that at time t, measured in years, the amount of the substance, in grams, given by the function f(x)=3e^-3t. What is the rate of...
*Tuesday, March 6, 2012 at 7:09pm by Matthew*

**Geology**

How do I do the foll9owing example? K-40 - A-40 (1.25 billion years) After careful analysis, a geochronologist determines that an unweathered, unmetamorphosed mineral sample contains 7 trillion atoms of the radioactive element K-40 and 105 trillion atoms of its decay product A...
*Thursday, October 25, 2012 at 6:40pm by Nicole*

**Chemistry**

The age of a rock can be estimated by measuring the amount of 40Ar trapped inside. The calculation is based on the fact that 40K decays to 40Ar by a first-order process. It also assumes that none of the 40Ar produced by the reaction has escaped from the rock since it was ...
*Thursday, May 21, 2009 at 3:46pm by Matt*

**physics**

Halflife for Sr-90 T =28.79 yr Decay constant λ=ln2/T =0.693/28.79•365•24•3600 = =7.63•10^-10 s^-1 Initial number of nuclei Nₒ=m/mₒ=4.8/89.9077•1.66•10^-27 = =3.2•10^25. Initial activity Aₒ = λ •Nₒ =7.63•10^-10 • 3.2•10^25= =2.44•10^16 Bq. A =...
*Sunday, June 3, 2012 at 9:02pm by Elena*

**Algebra I**

A sample of radioactive material weighing 45 grams has a decay rate of 4.25% each day. The equation y = 45(2.7)–0.0425t can be used to find the amount of material that still remains, where t is the number of days that have passed. Approximately what is the amount of material ...
*Tuesday, March 22, 2011 at 1:59pm by Sarah*

**CHEMISTRY**

Suppose you had a detection device that could count every decay event from a radioactive sample of plutonium-239.052156 (t1/2 is 24,000 yr). How many counts per second would you obtain from a sample containing 0.126 g of plutonium-239? (The mass of Pu-239 is 239.052156 u. ...
*Wednesday, September 5, 2012 at 9:17pm by Maryanne*

**Chemistry**

IT has too many neutrons, so it has to get rid of them. Beta decay would work. What would gamma decay accomplish here?
*Tuesday, March 4, 2008 at 5:25pm by bobpursley*

**Math+Growth/Decay**

The coefficient (which represents the original amount) can't be negative for growth or decay. Otherwise, you're correct.
*Wednesday, March 11, 2009 at 9:57pm by Toothpicks*

**Physics**

A first order exponential decay can be written as A(t)= Ae^(-t/r) where A(t) is the amount (of substance) after time t, A is the initial amount at time t=0 and r is the decay time. The fall time is defined as the time in which A(t) falls from 90% to 10% of its initial value. ...
*Saturday, October 11, 2008 at 10:12am by Beth*

**science**

Does anybody know any real life example of a nucleus Are you speaking of nucleus as in the nucleus of an atom or the nucleus of a living organism? If the former, the nuclear atom bomb or H bomb or the decay of radioactive materials to bombard some cancer patients to kill the ...
*Sunday, April 15, 2007 at 3:24pm by Amy L.*

**pre calculus **

The age of a document is in dispute, so archaeologists test for carbon-14. Due to radioactive decay, the amount A of carbon -14 present compared to the initial amount A0 after t years is given by the formula A(t) = A0e^-0.000124t . If 72% of the original amount of carbon- 14 ...
*Saturday, February 8, 2014 at 11:06pm by Raju*

**p**

A uranium nucleus (mass 238 u), initially at rest, undergoes radioactive decay. After an alpha particle (mass 4.0 u) is emitted, the remaining nucleus is thorium (mass 234 u). If the alpha particle is moving at 0.052 the speed of light, what is the recoil speed of the thorium ...
*Wednesday, March 14, 2012 at 6:57pm by opp*

**physics**

A uranium nucleus (mass 238 u), initially at rest, undergoes radioactive decay. After an alpha particle (mass 4.0 u) is emitted, the remaining nucleus is thorium (mass 234 u). If the alpha particle is moving at 0.055 the speed of light, what is the recoil speed of the thorium ...
*Monday, March 3, 2014 at 8:47pm by jill*

**physics**

Although most natural potassium nuclei are stable 39K (93.3%) or 41K (6.7%) nuclei, about 0.0117% are radioactive 40K nuclei, which have a half-life of 1.26 billion years. If you were worried about 40K radioactivity and wanted to wait for 97 % of the 40K in the environment to ...
*Thursday, June 6, 2013 at 1:21am by Anonymous*

**chemistry**

can you tell me how the beta-plus decay process may be understood (i) at the level of individual nucleons and (ii) at the level of quarks, by writing a decay reaction in each case.
*Saturday, May 2, 2009 at 1:49pm by mathew -b*

**Math**

Classify the model as exponential growth or exponential decay. Identify the growht or decay factor and the percent increase or decrease per time period.
*Thursday, November 4, 2010 at 7:16pm by Nikki*

**Chemistry**

It takes about 10^16 years for just half the samarium-149 in nature to decay by alpha-particle emission. Write the decay equation, and find the isotope that is produced by the reaction.
*Wednesday, July 14, 2010 at 4:09pm by Phillip*

**chemistry**

The radioactive waste must be discarded. The problem is that many of the radioactive isotopes have half lives of many years (some thousands of years) so where do we store that stuff and keep it out of harms way with no damage to humans or to the environment?
*Monday, November 14, 2011 at 8:43pm by DrBob222*

**chemistry (urgent)**

can you tell me how the beta-plus decay process may be understood (i) at the level of individual nucleons and (ii) at the level of quarks, by writing a decay reaction in each case.
*Saturday, May 2, 2009 at 2:36pm by mathew -b*

**Physics check**

Why does a hydrogen bomb produce significant radioactive fall-out? A hydrogen bomb operates with a nuclear reaction that produces radioactive products?
*Friday, April 25, 2008 at 8:22pm by Emily*

**precal**

If the half-life of a certain radioactive substance is 2000 years, estimate how many years must elapse before only 35% of the radioactive substance remains?
*Tuesday, January 22, 2013 at 10:15pm by james*

**Science**

What process involves the comparison of rock layers with others in a sequence to determine its age? radioactive decay radiometric dating relative dating absolute dating To determine the most accurate and precise age of Earth's oldest rocks, geologists would use relative dating...
*Wednesday, October 30, 2013 at 4:51pm by Abby*

**chemistry**

If there are 80 milligrams of a radioactive element decays to 10 milligrams in 30 minutes then what is the elements half life in minutes? Ok i narrowed it down to either 10 or 30...but im rly confused so if u could help it wuld be grea 80 40 1 min 20 2 min 10 3min looks like ...
*Sunday, March 4, 2007 at 7:19pm by jojo*

**Science**

135Xe that does not capture a neutron decays to Cs-135, one of the 7 long-lived fission products, while 135Xe that does capture a neutron becomes stable 136Xe. Estimates of the proportion of 135Xe during steady-state reactor operation that captures a neutron include 90%,[6] ...
*Tuesday, May 21, 2013 at 7:49am by bobpursley*

**Math+Growth/Decay**

3e^2x = G -3e^2x = G -3e^-2x = D 1/8e^2x = G -1/8e^-2x = D Would that be correct? I just made these examples up in my head. How can you tell if its growth or decay? I just look at the exponents. If is a negative then its decay? if its positive then its growth?
*Wednesday, March 11, 2009 at 9:57pm by Chopsticks*

**Physics**

200 kBq of activity is equivalent to 200*10^3 radioactive decays per second. This rate can be assumed to be constant. In one year, there will be (200*10^3 decays/s)*3600*24*365 s/yr) = 6.3*10^12 decays. Multiply this by 1.12*10^-14 J/decay for total Joules absorbed per year.
*Monday, May 17, 2010 at 3:03am by drwls*

**physics**

What they are calling the lifetime (2 microseconds) is actually about 1.28 half lives. There is no "end of life" number for a muon. Like all radioactivity, muons decay exponentially. I have some other objections to this problem. The "99.9% of the speed of light" number is too ...
*Sunday, March 20, 2011 at 10:20pm by drwls*

**Chemistry**

Hmmmm, the question sounds as if one believes proton decay actually exists. http://en.wikipedia.org/wiki/Proton_decay neutron decay: Now in the nucleus, neutrons do not decay, and again, your question baffles me. Free neutrons decay with "beta decay", the neutron emits an ...
*Friday, April 30, 2010 at 5:19pm by bobpursley*

**Chemistry**

radioactive sodium chloride is appropriate for diagnosing circulatory problems, but radioactive xenon is helpful in searching for lung problems. Explain why. I understand different elements are used for specific parts of the body but I don't understand this question. Thanks ...
*Sunday, April 14, 2013 at 8:06pm by Sara*

**chemistry**

One way in which atomic nuclear decay takes place?What is the significance of atomic nuclear decay? Analyze the societal implications of using this process.
*Tuesday, August 30, 2011 at 1:33pm by Boricua*

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