Sunday

September 21, 2014

September 21, 2014

Number of results: 536

**math**

Show that if a radioactive substance has a half life of T, then the corresponding constant k in the exponential decay function is given by k=-ln(2)/T I'm confused about how to show that that is true.
*September 4, 2014 by lucy*

**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.
*December 6, 2011 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.
*December 8, 2011 by Rock*

**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
*April 13, 2010 by lala*

**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
*September 17, 2010 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 very much!!
*June 3, 2011 by J. J. *

**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?
*May 12, 2013 by Taylor*

**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
*March 11, 2008 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?
*February 10, 2010 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?
*February 10, 2010 by ashley*

**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?
*December 5, 2012 by Molly*

**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.
*October 10, 2008 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?
*March 10, 2008 by Rachel*

**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?
*May 5, 2009 by Anonymous*

**Chem**

Radioactive 24Na with a half-life of 14.8 hours is injected into an animal in a tracer experiment. How many hours will it take for the radioactivity to fall to 12.5% of its original intensity? I am confused on what number to start with
*August 27, 2013 by Colby*

**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? .
*November 15, 2007 by Will*

**Science**

How much of a radioactive material with a half-life of 12,000 years is left after 36,000 years of decay?
*April 17, 2009 by Angie*

**chm**

An unknown radioactive substance has a half-life of 3.20 . If 34.8 of the substance is currently present, what mass was present 8.00 hours ago?
*February 10, 2012 by cp*

**Exponential decay**

Show that if a radioactive substance has a half life of T, then the corresponding exponential decay function can be written as y=y0e^kt
*September 4, 2014 by Adrianna*

**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?
*August 1, 2012 by Mira*

**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
*April 18, 2013 by j*

**Algebra**

What are some real-life examples of exponential decay? Please help me think of some ideas...except radioactive decay.
*January 30, 2014 by Anonymous*

**chemistry**

A radioactive sample contains 2.45 g of an isotope with a half-life of 3.8 days. How much of the isotope in grams will remain after 11.4 days?
*March 14, 2014 by Jacques*

**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!
*June 18, 2010 by Marie*

**precalculus**

Twenty percent of a radioactive substance decays in ten years. By what percent does the substance decay each year?
*March 3, 2011 by katrina*

**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
*April 17, 2011 by Sara*

**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?
*May 21, 2008 by ronny*

**chemistry**

a certain radioactive nuclide has a half life of 5.00 hour. Calcuate the decay rate for 1.000 mole of this nuclide __________ decay s-1
*July 12, 2012 by eric *

**College Algebra**

The half-life of a radioactive material is about 34.6 years. How much of a 1-gram sample of the material is left after 30 years?
*October 20, 2012 by Anonymous*

**Math/Calculus**

After 5 days, a particular radioactive substance decays to 37% of its original amount. Find the half life of this substance. Is this right? Th= ln 2/ln(1/.37) x 5 days
*October 17, 2011 by Christine*

**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? .
*November 18, 2007 by Will*

**Science**

Radioactive carbon-14 dating has determined that a fossil is 5.7 x 10 to the third power years old. What is the total amount of the original Carbon-14 still present in the fossil?
*March 24, 2010 by Gina*

**Calculus**

The amount A in grams of radioactive plutonium remaining in a 20-gram sample after t days is given by the formula A=20*(1/2)^(t/140). At what rate is the plutonium decaying when t=2 days?
*November 30, 2010 by Sara*

**calculus**

How do I set-up/solve this problem? Please help me. The half-life of the radioactive isotope gallium-70 is 20 minutes. If the initial amount of gallium-70 is 25 milligrams, when will 10 milligrams be left?
*February 17, 2011 by Melody*

**math**

How do I set-up/solve this problem? Please help me. The half-life of the radioactive isotope gallium-70 is 20 minutes. If the initial amount of gallium-70 is 25 milligrams, when will 10 milligrams be left?
*February 17, 2011 by Amy*

**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?
*October 25, 2011 by Josh*

**TO ANY SCIENCE HELPER**

I honestly don't get how to use radioactive dating to determine the age of a sample. I need an example and what to do in order to get the answer. I need it to be step by step. Thank u so much :)
*April 17, 2014 by Anonymous *

**chem**

A typical dose of a radioactive sample is 27.0 mCi. How long does it take for the activity to reduce to 0.100 mCi? The half life of the sample is 211,000 y.
*September 19, 2014 by bekah*

**mathematics**

what is the equation for exponetial decay(radioactive decay) and how to use the half life in the equation
*November 2, 2011 by anonymous*

**physic**

In a serious accident, a nuclear power plant's reactor vessel cracks, and all of the cooling water drains out. Although nuclear fission stops, radioactive decay continues to heat
*May 6, 2014 by joseph*

**Elem. Ed.**

b and c, don't you think? the teacher explains and the children practice what has been explained my experience leads to me to the conclusion that actual practice is the best learning technique. I vote for c. sounds good Can you help me with this question? An instructional ...
*April 17, 2007 by jules*

**Physics check**

A certain radioactive isotope has a half-life of one hour. At noon, 100g of the material is present. How much of the original isotope will be present at 3:00 p.m.----1/8 6:00 p.m.-----1/16 10:00 p.m.-----1/32 Are these correct?
*April 21, 2008 by Sara*

**chemistry**

A radioactive sample contains 2.45g of an isotope wiht a half life of 3.8 days. How much of the isotope in grams remains after 11.4 days? please explain
*November 26, 2011 by Monique*

**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
*December 2, 2012 by steve b*

**math**

A quantity of oxygen gas had 16.32 g of the radioactive isotope oxygen-19 in it. When measured exactly 10 minutes later, the amount of oxygen-19 was 0.964 g. What is the half-life, in seconds, of oxygen-19?
*March 17, 2013 by Matthew*

**Maths**

A radioactive substance decays exponentially in such a way that after 50 years, 60% of the initial amount remains. Find an expression for the quantity remaining after t years.
*June 15, 2014 by Rish*

**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...
*November 27, 2010 by Jane*

**Physics**

University students, studying the activity of a particular radioactive isotope which had a half-life of 12.0 hours. If the original activity of the sample was 448 kBq, what would the activity be 3.00 days later?
*May 16, 2010 by Anonymous*

**music**

I have chosen Radioactive for my musical dance routine with my friend. I love this website and Radioactive. So.. I need a bit of help. I'm sticking to the song no matter what and I need advice from music tutors. This is what I have so far: Song playing in the background via ...
*June 7, 2014 by Emz*

**Elem. Ed.----- I Need Help!!!**

Can you help with this question? 1. Charts do not: A. offer an opportunity for shared experiences. B. allow the print to stand out. C. capture the children's attention. D. teach children to read at a very early age. I know charts (A) offer opportunities for shared experiences,...
*September 21, 2007 by Anonymous*

**Elem. ED.**

Art and math are being integrated when students: 1. draw more than 1 picture on a page. 2. use rectangular paint pots. 3. identify geometric shapes when composing a picture. 4. insist on using the same materials as their peers. Is the 3rd answer correct? "identifying geometric...
*April 9, 2007 by Keisha*

**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?
*April 8, 2010 by Zoa*

**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?
*April 8, 2010 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?
*April 8, 2010 by Moe*

**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?
*January 11, 2012 by Heather*

**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.
*February 22, 2014 by sara*

**Earth Science**

Describe how Earth would be different today if. It contained no radioactive material. What would the consequences be for the Earth's interior layer?
*September 30, 2009 by Breanna*

**Earth Science**

Describe how Earth would be different today if it contained no radioactive material. What would the consequences be for the Earth’s interior layers?
*December 2, 2010 by Jack*

**Chemistry**

32P is a radioactive isotope with a half-life of 14.3 days. If you currently have 48.1 g of 32P, how much 32P was present 3.00 days ago?
*June 10, 2012 by Anonymous*

**algebra**

Julie has 250 grams of a radioactive substance. The substance decays every hour. How long will it take until she has 20 grams of the substance left?
*September 9, 2013 by Sozy *

**Radioactivity or science**

A radioactive isotope source has a mass of 120ug. If the isotope had a half life of 20s, what would be the mass if the isotope after 2 mins?
*April 21, 2014 by Jannet*

**chem**

a radioactive fission product of nuclear explosions and sccidents is often iodine 131 which becomes distributed in the atmosphere. this falls upon the ground and is absorbed by plants. explain how this radiation could eventually beome concentrated in the human body and cause ...
*February 3, 2008 by Amanda*

**chemistry**

a radioactive fission product of nuclear explosions and sccidents is often iodine 131 which becomes distributed in the atmosphere. this falls upon the ground and is absorbed by plants. explain how this radiation could eventually beome concentrated in the human body and cause ...
*February 4, 2008 by Amanda*

**elem math**

can some help me with my daughters homework. what figure is part of a line and has two endpoints? does a door have angles like a right , smaller or lager then a right angle? Seth made a picture frame with 4 equal sides and a right angle at each corner, what word best describes...
*February 19, 2008 by Mrs.Green*

**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
*December 13, 2013 by victoria*

**Radioactivity **

How are the terms "activity" and "becquerel" related? A radioactive isotope source has a mass of 120 g. If the isotope has a half life of 20 secs what would be the mass of the isotope in 2 mins?
*April 16, 2014 by Anonymous *

**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?
*July 27, 2010 by Jin*

**Chemistry**

A 71 mg sample of a radioactive nuclide is administered to a patient to obtain an image of her thyroid. If the nuclide has a half-life of 12 hours, how much of the nuclide remains in the patient after 4.0 days?
*October 5, 2010 by Mr.Chemistry*

**Chemistry**

All isotopes of technetium are radioactive, but they have widely varying half-lives. If an 800.0 g sample of technetium-99 decays to 100.0 g of technetium-99 in 639,000 y, what is its half life
*December 11, 2012 by Matthew*

**science**

The thermal energy of volcanoes and natural hot springs comes from trace amounts of radioactive minerals in common rock in the Earth's interior. Why isn't the same kind of rock at the Earth's surface warm to the touch?
*January 30, 2008 by Ashton*

**earth science**

what would be the chart to use for carbon 14 whcih has a half life of 5730 years and a piece of wood which originally has 12 grams pf radioactive isotope; If the half lives occurred and now has 0.75 grams left?
*November 29, 2012 by lan*

**Elem. Ed.**

Can someone please give me input on this question? Complete immunization is usually required of chldren: 1.who will be turning 2 years old. 2.before they can travel across state line. 3.at the time they enroll in childcare programs. This question is confusing because when ...
*April 15, 2007 by Keisha*

**Algebra**

In 10 years, 25% of a radioactive substance decays. What is its half-life? A. 25 years B. 24 years C. 20 years D. 29 years
*December 12, 2012 by Darwin12*

**Math**

In 10 years, 25% of a radioactive substance decays. What is its half-life? A. 25 years B. 24 years C. 20 years D. 29 years
*December 14, 2012 by Darwin12*

**chemistry**

radioactive disintegration is 1st order reaction. calculate the age of ancient wood piece if it shows a c14 activity of 20% compared to present day wood. if the half change time for c14 is 5600 years
*December 5, 2011 by pinky*

**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?
*December 2, 2010 by Kiesha*

**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 by andrew*

**chemistry**

Cobalt-60 is radioactive isotope used to treat cancers. A gamma ray photon emitted by this isotope has an energy of 2.13 x 10—13 J. What is the wavelength of this gamma ray in SI unit?
*April 7, 2011 by John*

**Physics**

Consider a radioactive sample with a half-life of one week. How much of the original sample will be left at the end of the second week? The third week? The fourth week?
*August 29, 2013 by Tracee*

**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?
*September 26, 2012 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.
*January 26, 2014 by barbara*

**Physics**

Suppose a hypothetical radioactive nucleus (Hy) has a half-life of 10 days. If we have 80 gms of the substance at the start of an experiment, how many gms of the substance will remain undecayed after 30 days
*May 10, 2008 by Tim*

**Physic II**

The decay constant of a radioactive nuclide is 9.5x10^-3 s^-1 . At given instant, the activity of a specimen of the nuclide is 80 mCi. The time interval required for the activity to decline to 40 mCi is closest to: ?
*April 30, 2014 by huline3*

**Half-life**

After two hours, 1/16 of the initial amount of a radioactive isotope remains undecayed. What is the half-life of the isotope?
*November 18, 2013 by Andrea*

**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?
*May 1, 2011 by Anonymous*

**chemistry**

Radioactive decay is a process that follows first-order kinetics. The half-life of 32P is 0.03920 years; how long (in minutes) would it take for the amount of 32P to decrease to 53.25% of its initial amount? I don't understand at all what to do here
*May 11, 2014 by sara*

**chemistry**

How long will it take for 25% of the C-14 atoms in a sample of C-14 to decay? The half-life for the radioactive decay of C-14 is 5730 years. If a sample of C-14 initially contains 1.1 mmol of C-14 , how many millimoles will be left after 2275 years?
*February 28, 2010 by Anonymous*

**Math**

A 15-g sample of radioactive iodine decays in such a way that the mass remaining after t days is given by m(t) = 15e^(−0.051t), where m(t) is measured in grams. After how many days is there only 3 g remaining?
*April 22, 2013 by Zach*

**chemistry**

Radioactive materials are often used in biological studies. A radiation biologist studies the rate of decomposition of a certain substance and obtains the following data: Time(days) 0 4.0 8.0 12.0 16.0 Mass (μg) 15.50 10.90 7.67 5.39 3.79 Determine the rate constant in ...
*February 4, 2012 by L*

**Chemistry**

A viral contains radioactive iodine -131 with an activity of 2.0 mCi per milliliter. If the thyroid test requires 3.0 mCi in an "atomic cocktail", how many milliliters are used to prepare the iodine -131 solution ?
*July 20, 2010 by Anonymous*

**Chemistry**

Cobalt-60 is a radioactive isotope used to treat cancers. A gamma ray emitted by this isotope has an energy of 1.33 MeV (million electron volts; 1 eV = 1.602 multiplied by 10-19 J). What is the frequency (in Hz) and the wavelength (in m) of this gamma ray?
*November 21, 2010 by Rachel*

**Science**

A radioactive substance is found to register 1000 counts per second on a Geiger counter. Twenty-four hours later it registers 125 counts per second. What is its half-life?
*December 5, 2012 by Owen*

**Chemistry **

IF 80mg of a radioactive element decays to 10mg in 30 minutes, the half-life of this element is a.10 min b.20 min c.30 min d.40 min the answer is a.10 min but i would like to know why, please help.
*May 30, 2011 by Jazmin *

**college**

if a sample of the radioactive nuclide 139cs has an activity of 0.0730 ci, what is the instantaneous rate of decomposition of 139cs in terms of grams per second? the mass of 139cs is 138.9134 amu. 1 ci 3.700 × 1010 disintegrations/ s, 1 amu 1.66054 ×10–24 g
*May 3, 2010 by Anonymous*

**Chem**

If a sample of the radioactive nuclide 139Cs has an activity of 0.0730 Ci, what is the instantaneous rate of decomposition of 139Cs in terms of grams per second? The mass of 139Cs is 138.9134 amu. (1 Ci = 3.700 × 1010 disintegrations/s, 1 amu = 1.66054 × 10–24 g)
*May 3, 2010 by Alicea*

**Elem. Ed.**

Please look over these questions and my answers to see if I have chosen the most appropriate answer. 1. Luis is being introduced to the finger play "Friends at Play." It is very likely that Luis will: A. do the finger movements first. B. learn the words first. C. not ...
*September 17, 2007 by Anonymous*

**Science**

Suppose you had two samples of the same radioactive isotope one that weighs 25g and one that weighs 50g would the same number of particles be ejected from each sample in the first hour,explain.
*October 10, 2011 by Anonymous*

**Physics**

An alpha particle (mass=6.68x10^-27kg)is emitted from a radioactive nucleus with an energy of 5.00MeV. How fast is the alpha particle moving in m/s? (1 MeV= 1.6x10^-13J). I dont know how to start to solve this problem A.2.40x10^7 m/s B.1.55x10^7 m/s C.3.70x10^6 m/s D.1.85x10^6...
*January 10, 2011 by Matt*

**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
*May 28, 2012 by star*

**science **

The half-life of carbon 14 is 5730 years. if a 1 g sample of old carbon is 1/8 as radioactive as 1 g of a current sample, then the age of the old sample is about ___________years. 22,900 17,200 11,500 716
*March 5, 2012 by chuck *

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