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April 20, 2014

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Number of results: 691

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

Elem. Ed.
Can you help me to fill in the blank to this sentence? Molly is an older 4-year-old and her teacher is concerned about her _________ speech development because she is difficult to understand and this has not changed in the last year. 1. receptive 2. expressive 3. rate of ...
Friday, April 13, 2007 at 10:09pm by Keisha

chemistry
Write a balanced nuclear equation for the positron emission of each of the following radioactive isotopes: silicon-26,mercury-188,7737Rb,9345Rh
Thursday, December 5, 2013 at 5:08pm by lana

Physical Science
This reference may be useful. (Broken Link Removed) You may have some difficulty finding a radioactive source with a half-life short enough to measure. Most are used in nuclear medicine, with carefully limited distributiuon. My son once did a science fair experient like yours...
Tuesday, November 13, 2007 at 5:46am by drwls

Maths
You can convert a fraction into a decimal by dividing the top number (numerator) by the bottom number (denominator). Here's an example: 1/2 = 1 ÷ 2 = 0.5 (= 50%) Try it with the others. Here are some good math websites to help with fractions, decimals, and many other math ...
Saturday, December 12, 2009 at 8:52am by Writeacher

earth science
how does radioactive decay provide heat energy within the earth
Saturday, July 19, 2008 at 3:06pm by kate

earth
how Earth would be different today, if it contained no radioactive material
Tuesday, November 3, 2009 at 4:43pm by Lizeth

elem math
jenna drew a triangle with 1 right angle. what type of triangle did she draw? Can a triangle 2 right angles? trinka stood inside a circle of friends to play a game. each friend in the circle is the same distance from trinka. what part of the circle does trinka's position ...
Tuesday, February 19, 2008 at 8:52pm by Mrs.Green

chem
what changes in atomic number and mass number occur in a positron emmision of radioactive decay?
Monday, June 2, 2008 at 8:12pm by jerson

Physics
How many half-lives are required for the number of radioactive nuclei to decrease to 1/10^4 of the initial number?
Friday, July 27, 2012 at 5:17pm by Beth

Math
Find the half-life (in hours) of a radioactive substance that is reduced by 10 percent in 5 hours.
Tuesday, August 28, 2012 at 6:58pm by David

Physics
The decay process is explained better at http://en.wikipedia.org/wiki/Cobalt-60 Each Co-60 nucleus results in one beta electron and two gamma photons. That is three nearly simultaneous radioactive emission processes during the each transmutation, with a 5.27 year half life. ...
Thursday, November 20, 2008 at 4:55am by drwls

Science
It must have a quantum mechanically allowed orbit there. A few isotope nuclei do capture electrons that get too close. This results in radioactive or X-ray emission.
Friday, June 27, 2008 at 9:47pm by drwls

Calculuc
How do you set up this problem? The decay constant for the radioactive element cesium 137 is .023 when time is measured in years. Find its half-life.
Wednesday, August 22, 2012 at 9:28am by Jillian

college algebra
In 4 years, 30% of a radioactive element decays. Find its half-life. (Round your answer to one decimal place.) _____ yr
Sunday, November 17, 2013 at 3:10pm by Dee

Chemistry
The answer will also explain why we don't see compounds of that element in the chemistry lab. Unstable isotopes are radioactive!
Tuesday, May 26, 2009 at 4:38pm by PC

Biology - fossils
Creationists do not believe in radioactive carbon dating, so they won't agree that there could be fossils older than Adam and Eve
Friday, March 2, 2012 at 6:26pm by drwls

chemistry
Which radioactive emanations have a charge of -1? beta particles alpha particles gamma rays neutrons
Monday, April 30, 2012 at 12:02am by david

earth
Some of these sites might help you: http://www.google.com/search?q=how+Earth+would+be+with+no+radioactive+material&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a Sra
Tuesday, November 3, 2009 at 4:43pm by SraJMcGin

Calc
Radioactive radium () has a half-life of 1599 years. What percent of a given amount will remain after years?
Sunday, April 15, 2012 at 11:07pm by Pamela

physics
If a radioactive isotope has a half-life of 1 year, how much of the original sample will be left at the end of the 2nd year?
Thursday, August 23, 2012 at 9:50am by Anonymous

Physics
A radioactive substance decays from 2.0kg to 1.6kg in 156 days. What is the decay constant and the half life of the substance?
Tuesday, August 6, 2013 at 11:28pm by Alice

Physics
A radioactive substance decays from 2.0kg to 1.6kg in 156 days. How much will be left after 201 days?
Wednesday, August 7, 2013 at 9:45am by Alice

isd muscat
after two hours 1/16th of the radioactive isotope remains undecayed.half life of the isotope is
Friday, April 11, 2014 at 3:48am by saritha

science
Can someone help me find two specific reasons why radioactive dating/geology are evidence for evolution. I've read many articles online but i do not really understand the whole concept.
Saturday, June 14, 2008 at 8:25pm by Anonymous

Math/Radioactive Dating
Whats In? I'm so confused :( We were told to figure this out using half-life. Our prof didn't even use logs or anything of that sort.
Saturday, February 19, 2011 at 5:56pm by Lena

science
the threat of global warming is mainly associated with ? 1 radioactive wastes 2 use of hydroelectric energy 3 burning of fossil fuels 4 thermal pollution of lakes and rivers
Tuesday, May 29, 2012 at 7:44pm by amber

Science
if a radioactive isotope has a half-life of one year, how much of the original sample will be left at the end of the second year?
Thursday, August 23, 2012 at 9:53am by aileen

Science
if a radioactive isotope has a half-life of one year, how much of the original sample will be left at the end of the second year?
Thursday, August 23, 2012 at 9:59am by aileen

Chemistry
A radioactive element has a half-life of 6.41 days. What percent of the original sample will be left after 15.0 days?
Sunday, January 6, 2013 at 2:27pm by John

calculus
Carbon-14 is a radioactive substance produced in the Earth's atmosphere and then absorbed by plants and animals on the surface of the earth. It has a half-life (the time it takes for half the amount of a sample to decay) of approximately 5730 years. Using this known piece of ...
Friday, July 24, 2009 at 1:11pm by j

math for elem. teacher
two consecutive? one is odd, the ohter even. So this one will be divisible by two. Which means the product is divisible by two, even if b=a/2 cb=ca/2 so cb is even.
Friday, February 10, 2012 at 9:46pm by bobpursley

Chemistry
Thinking about the uses of radioactive isotopes, which statement is true? A. The iodine isotope, I-27, is used to diagnose thyroid disorders. B. Radiation may be detected because it ionizes the atoms it affects. C. Its clearly understood that irradiating food kills bacteria ...
Thursday, June 24, 2010 at 8:56pm by Sadie

Math/Radioactive Dating
But it does make a difference if we solve the problem as ln(No/N) = kt as I first responded. Log(No/N) = kt won't work, or at last I don't think it will.
Saturday, February 19, 2011 at 5:56pm by DrBob222

math
Radioactive radium has a half-life of approximately 1599 years. What percent of a given amount remains after 100 years?
Thursday, February 24, 2011 at 7:53pm by rachel

math
Radioactive radium has a half-life of approximately 1599 years. What percent of a given amount remains after 100 years?
Thursday, February 24, 2011 at 7:59pm by rachel

chemistry
a radioactive material is undergoing nuclear decay. After 40 minutes, 25% of the sample remains. What is the half-life of the sample
Saturday, August 27, 2011 at 9:00am by marjani

science
I need a picture that describes radioactive decay, fussion and fision. Someone said that they would give me a link earlier but they didnt. Thank you! This website helps me out so much.
Thursday, January 15, 2009 at 5:05pm by Amy

chemistry
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?
Thursday, May 12, 2011 at 5:23pm by brittany

Chemistry
If 30% of a sample of radioactive isotope decays in 24 hrs, what is the half-life? How do i know which order to use? and do I convert hr to mins or seconds? Pls help for my exam tomorrrow
Thursday, February 23, 2012 at 2:44pm by tina

chemistry
I am having trouble understanding what the concept is for writing these out. Write a balanced nuclear equation for the alpha decay of each of the following radioactive isotopes: curium-243, 22589Ac
Thursday, December 5, 2013 at 9:40am by ellie

Biology-check my answer
Hershey and Chase used the 35S isotope to label proteins. How does this isotope differ from the 32S isotope found in greatest natural abundance, and why did they choose 35S instead of 32S? A)35S has more protons than 32S; Hershey and Chase used it because it has a greater mass...
Wednesday, December 19, 2012 at 4:11pm by joey

algebra
Scientists can determine the age of ancient objects by a method called radio carbon dating. The bombardment of the upper atmosphere by cosmic rays converts nitrogen to a radioactive isotope 14C of carbon with a half-life of about 5710 years. Vegetation absorbs carbon dioxide ...
Thursday, March 7, 2013 at 10:39pm by Emily

Chemistry please check
Ok except for #1. U is a radioactive element, naturally. There is a series for U-238, another series for U-235, and a third for Th-232. All end in Pb.
Friday, February 15, 2008 at 11:35pm by DrBob222

Chemistry
The nuclide 12 N 7 is unstable. What type of radioactive decay would be expected??? my guess is either gamma or beta. are either of those correct?
Tuesday, March 4, 2008 at 5:25pm by Jonathan

math
if the rate for radioactive decay for a substance is r=-.0063 and time is being measured in days how do you find the half-life of the substance to the nearest hour?
Monday, March 30, 2009 at 1:16am by mike

physics
Fluorine 20 is radioactive and Na 23 is not None of the reasons listed apply. F-20 just has more neutrons than the nucleus "needs"
Friday, September 17, 2010 at 9:54pm by drwls

ALGEBRA
You have 480 grams of a radioactive kind of tin. If its half-life is 10 days, how much will be left after 30 days?
Wednesday, March 21, 2012 at 12:59pm by Anonymous

Science
If a 20 gram sample of a radioactive substance has a half-life of 6000 years, how many grams would be present after 18000 years?
Wednesday, December 5, 2012 at 4:21pm by Owen

science
If it is still living, then it is still growning. Where would you get tissue which was produced eons ago? Only long dead things can be radioactive dated.
Monday, February 10, 2014 at 5:43pm by bobpursley

chemistry
use logic and simple math to determine how long it will take for a sample of potassium- 42 to decay from 8mg to 0.25mg if the half-life of this radioactive isotope is 124 hours
Tuesday, October 12, 2010 at 8:29pm by jay 1

biology
You might begin here: http://www.google.com/search?q=use+of+radioactive+dating+to+tell+a+rock%27s+age&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a Sra
Thursday, January 7, 2010 at 4:40pm by SraJMcGin

9th grade math
Here is a causal relatlionship. The amount of radioactive decayed products depends on the time since it was formed. Amount=OriginalAmount* e^(t/k) where k is a constant.
Thursday, March 5, 2009 at 8:20pm by bobpursley

Calculus
A certain radioactive material decays exponetially. The percent, P, of the material left after t years is given by P(t)= 100(1.2)^-t a)Determine the half life of the substance
Tuesday, April 13, 2010 at 7:43pm by lala

math
The decay of 333 mg of a radioactive substance is given by A(t) = 333e-0.024t, where t is time in years. Find the amount left after 17 years.
Friday, April 8, 2011 at 7:17pm by allison

Alg2
Radioactive iodine is used to determine the health of the thyroid gland. It decays according to the equation y=ae -0.0856t where t is in days. Find the half-life of this substance. Round to the tenths place.
Tuesday, December 6, 2011 at 9:50pm by Rock

Alg2
Radioactive iodine is used to determine the health of the thyroid gland. It decays according to the equation y=ae -0.0856t where t is in days. Find the half-life of this substance. Round to the tenths place.
Thursday, December 8, 2011 at 7:37pm by Rock

Chemistry
Tc-99 is a radioactive isotope that decays by beta emission and is used by radiologists in the diagnosis of liver disease. Its decay behavior is shown by the activity-time table. What is its half-life?
Saturday, December 10, 2011 at 11:49pm by Jennifer

chemistry
What are some applications of Nuclear Chemistry in Medicine? So far I've found - X-rays - Radioactive tracers - Gamma radiation can be used to treat cancer and other diseases
Tuesday, March 11, 2008 at 8:05pm by william

college
The average number of radioactive particles passing through a counter during 1 millisecond in a lab experiment is 4. What is the probability that more than 2 milliseconds pass between particles?
Wednesday, February 10, 2010 at 9:09pm by ashley

statistics
The average number of radioactive particles passing through a counter during 1 millisecond in a lab experiment is 4. What is the probability that more than 2 milliseconds pass between particles?
Wednesday, February 10, 2010 at 10:32pm by ashley

Physics
In the radioactive formula 235 U → 235 Np + X, what does X represent 92 93 A. An Alpha Particle B. A positron C. An electron D. A gamma ray Please help ASAP!!! Thank you :D
Friday, June 3, 2011 at 4:32pm by J. J.

elem alg
On a certain test, the student gets 3 points for each correct answer and loses 2 points for each incorrect answer. The test has 37 questions total. (no question can be lfet blank.) If x is the number of answers a students gets correct, write and express fro the students total ...
Thursday, March 10, 2011 at 12:11am by Vera

Elem. Ed.
It is confusing because it has given you two correct answers. It's a poorly written question. If you have the option, put down both answers. If you don't have the option of two answers, then I suggest you stick with B, learning to form letters. It may be that a child who has ...
Thursday, September 20, 2007 at 6:57pm by Ms. Sue

Math/Radioactive Dating
I got your answer as well. Teachers do make mistakes. I make about 2 per day, but my wife tells me I make more than that.
Saturday, February 19, 2011 at 5:56pm by Reiny

Physical Science
I'm still working on getting a fireman to come out to the school to demonstrate a radioactive detector. No luck so far. This is for a project on Marie Curie. Any other suggestions would be greatly appreciated.
Friday, October 10, 2008 at 3:47pm by jules

Physical Science
The heat of volcanoes and hot springs comes from trace amounts of radioactive minerals found in the Earth's interior. Why isn't the same rock at the Earth's surface warm?
Monday, March 10, 2008 at 6:10pm by Rachel

Physics
It got posted incorrectly: In the radioactive formula, 235/92 U → 235/93 Np = X, what does X represent A. An alpha Particle B. A positron C. An electron D. A gamma ray
Friday, June 3, 2011 at 4:20pm by J. J.

Physics
This website doesn't post correct :/ In the radioactive formula 235 U → 235 Np + X, what does X represent 92 93 A. An Alpha Particle B. A positron C. An electron D. A gamma ray
Friday, June 3, 2011 at 4:20pm by J. J.

Physical Science- Help Please!
Suppose that you are given a 100 gram sample of a radioactive substance with a half-life of 32 days. How many grams will be left after 192 days?
Wednesday, December 5, 2012 at 4:13pm by Molly

College algebra
The radioactive element has a half-life of about 28 years and sometimes contaminates the soil. After 47 years, what percentage of a sample of the elements remain?
Sunday, May 12, 2013 at 4:20pm by Taylor

physics
The half-life of a certain radioactive isotope is 32 hours.What fraction of the sample would remain after 16 hours?(a)0.50(b)0.25(c)0.62(d)0.71
Sunday, September 22, 2013 at 1:11pm by john

Elem. Ed.
I AM A PARENT,I THINK THE TEACHER NEEDS TO TAKE CHARGE OF HER OWN CLASS ROOM AND WHEN THE TEACHER FEELS ITS TIME TO GO.THAN ITS TIME TO GO,US PARENTS STICK AROUND TO MAKE OUR SELVES FEEL BETTER EVEN WHEN OUR CHILDREN ARE FINE,ITS HARD TO SAY GOOD BYE,SO TELL US WHEN YOU FEEL ...
Friday, May 4, 2007 at 7:52am by mrs.north

Physics
In the radioactive formula, 235 U → 235 Np = X, what does X represent 92 93 A. An alpha Particle B. A positron C. An electron D. A gamma ray Please help ASAP!!! Thank you very much!!
Friday, June 3, 2011 at 4:20pm by J. J.

physical sciences
Eight is correct for the number of neutrons. Carbon-14 is an important isotope used for radioactive dating of carbon-containing organic matter. Its half life is 5568 years.
Tuesday, May 22, 2012 at 9:02am by drwls

physical science
A certain radioactive substance has a half-life of 1 hour. If you start with 1 gram of the material at noon, how much will be left at 3:00 P.M.? At 6:00 P.M.? At 10:00 P.M.?
Wednesday, November 2, 2011 at 10:08pm by cheryl

Science
Half-life T is the time during which the number of decaying species decreases by half Decay Law N=Nₒexp(-λt) Decay constant λ=ln2/T. Half-life T is the time during which the number of decaying species decreases by half If t=T, then N= Nₒexp(-λT...
Monday, July 16, 2012 at 4:50am by Elena

math
39mg radioactive with 1/2 life is decay total in 2.5 years. How many mg it remain if half of the amount is decay in 2 years? Thank you!
Friday, June 18, 2010 at 9:49am by Marie

Chemistry
If the amount of radioactive iodine-123 in a sample decreases from 0.8 g to 0.1 g in 36.2 hours, what is the half-life of iodine-123
Sunday, April 17, 2011 at 10:22am by Sara

Environmental Science 11th grade
If half of a quantity of radioactive material decays in 10 years, in another 10 years?
Thursday, February 7, 2013 at 12:34pm by AM

Science
Radioactive decay law N =N₀exp(-λt)= =N₀exp(-ln2t/T)= =20exp(-0.69318000/6000) = 2.5 g
Wednesday, December 5, 2012 at 4:21pm by Elena

Algebra
What are some real-life examples of exponential decay? Please help me think of some ideas...except radioactive decay.
Thursday, January 30, 2014 at 5:47pm by Anonymous

precalculus
Twenty percent of a radioactive substance decays in ten years. By what percent does the substance decay each year?
Thursday, March 3, 2011 at 5:40pm by katrina

Science
How much of a radioactive material with a half-life of 12,000 years is left after 36,000 years of decay?
Friday, April 17, 2009 at 1:29pm by Angie

Pre calc
If 250 mg of a radioactive element decays to 200 mg in 48 hours, find the half-life of the element
Wednesday, April 28, 2010 at 10:06pm by Dom

math
A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.
Thursday, February 3, 2011 at 1:44am by Eric

math
A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.
Thursday, February 3, 2011 at 1:45am by Eric

math
A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.
Thursday, February 3, 2011 at 1:45am by Eric

math
A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.
Thursday, February 3, 2011 at 1:45am by Eric

math
A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.
Thursday, February 3, 2011 at 1:45am by Eric

math
A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.
Thursday, February 3, 2011 at 1:45am by Eric

math
A 10 kg quantity of a radioactive isotope decays to 3 kg after 17 years. Find the decay constant of the isotope.
Thursday, February 3, 2011 at 1:45am by Eric

physics
The half life of a radioactive sample is 6.93 days.after how many days will only one -tenth of the sample be left behind?
Wednesday, August 1, 2012 at 2:37am by Mira

Chemistry
A 208 g sample of sodium-24 decays to 13.0 g of sodium-24 within 60.0 h. What is the half-life of this radioactive isotope?
Tuesday, December 11, 2012 at 11:08pm by Matthew

chemistry
if the amount of radioactive iodine-123 in a sample decreases from .400g to .100g in 26.2 hours, what is the half-life of iodine-123
Thursday, April 18, 2013 at 7:23pm by j

physics
Suppose 32000 radioactive nuclei are in a sample. About how many remain after two days if the half-life is 22 hrs? What is the initial activity of the sample in decays per minute?
Tuesday, May 5, 2009 at 10:06am by Anonymous

phyics
Pick the radioactive isotope in each set. 23/11 20/9 Explain your choice. a)its atomic number is greater than 83 b)it has fewer n than p in the nucleus c)it is an odd-odd nuclide none of the above
Friday, September 17, 2010 at 4:20pm by ashley

physics
Pick the radioactive isotope in each set 23/11 na or 20/9 f explain why a)its atomic number is greater than 83 b)it has fewer n than p in the nucleus c)it is an odd-odd nuclide none of the above
Friday, September 17, 2010 at 9:54pm by Ashley

PHYICS
Pick the radioactive isotope in each set 14/7 N OR 23/13 AL EXPLAIN A)its atomic number is greater than 83 B)it has fewer n than p in the nucleus C)it is an odd-odd nuclide none of the above
Saturday, September 18, 2010 at 11:51am by Ashley

physics
if 5/6th of a radioactive sample decay in 70 years and 1/6th remain. how can you find the half life without knowing the decay constant can you help?
Wednesday, May 21, 2008 at 5:51am by ronny

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