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April 18, 2014

Search: Physics - Half life

Number of results: 128,895

chemistry
What is the half-life of a compound if 69 percent of a given sample of the compound decomposes in 59 min? Assume first-order kinetics.
Sunday, January 31, 2010 at 11:28pm by danielle

chemistry
For the reaction A to products}, the following data were obtained: t=0 s, A}]=0.715 M; 22 s, 0.605 M; 74 s, 0.345 M; 132 s, 0.055 M. What is the half-life of the reaction?
Sunday, February 28, 2010 at 6:31am by joe

chemistry
For the reaction A to products}, the following data were obtained: t=0 s, A}]=0.715 M; 22 s, 0.605 M; 74 s, 0.345 M; 132 s, 0.055 M. What is the half-life of the reaction?
Sunday, February 28, 2010 at 5:36pm by joe

chemistry
For the reaction A to products}, the following data were obtained: t=0 s, A}]=0.715 M; 22 s, 0.605 M; 74 s, 0.345 M; 132 s, 0.055 M. What is the half-life of the reaction?
Sunday, February 28, 2010 at 8:43pm by joe

Math
The half-life of strontium-90 is 28 years. How long will it take a 60 mg sample to decay to a mass of 15 mg?
Wednesday, May 19, 2010 at 7:17pm by Caitlyn

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

chemistry
caffeine has a half-life of 4.6 hours in the human body.. How long would it take 125 milligrams tritium to decay to 22 milligrams?
Monday, April 11, 2011 at 7:07pm by cam

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

College Math
Only 43% ofthe carbon-14 in an artifact remains. How old is the artifact? Would the answer be less than the half life?
Sunday, February 19, 2012 at 7:57pm by Angel

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

Algebra 2
half life carbon -14 is 5,730 years. If you start out 50 grams, how long will it take until it reaches 2 grams?
Sunday, May 20, 2012 at 6:54pm by chels

Science
A certain isotope has a half-life of 12 hrs. How long will it take for 100 gr to decay into only 25 gr?
Sunday, July 15, 2012 at 12:37pm by Haley

Science chemistry
It takes 1 hour and 17 min. for a 1.000gsample of a certain isotope to decay to 0.121g. What is the half-life of this isotope? plssss helpp
Monday, September 24, 2012 at 1:22pm by Shay

chemistry
It takes 1 hour and 17 min. for a 1.000g sample of a certain isotope to decay to 0.121g. What is the half-life of this isotope? plssss helpp
Monday, September 24, 2012 at 4:42pm by Shay

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

Chemistry
The half-life of a first order reaction is determined to be 92.0 years. How long will it take for the concentration of the reactant to reach 2% of its initial value?
Saturday, December 15, 2012 at 4:18pm by Chemistry

UIW
Neptunium-239 has a half-life of 2.35 days. How many days must elapse for a sample of 239Np to decay to 0.100% of its original quantity
Thursday, September 19, 2013 at 1:32am by Anonymous

math
3. The half-life of a certain drug in the human body is 8 hours how long it would take for a dose of this drug to decay to 0.1% of its initial level?
Tuesday, November 12, 2013 at 6:52pm by hannah

physics help!!
A body at given uniform temperature of 300K and internal energy 8x10^6 J is split in two equal halves: a)Has any heat been exchanged b)What is the temperature of each half? c)What is internal energy of each half? K=Kelvin
Wednesday, November 17, 2010 at 10:27pm by carla

maths
No. 27 is half of 54. If half of the fruits are oranges and half are bananas, then the orange-to-banana ratio would be 1:1 (for every 1 orange there is 1 banana). That's not what you want.
Thursday, February 4, 2010 at 2:57am by Anonymous

physics
weight = 1.6 * 9.8 = 15.68 N T in each side of wire do right half, left the same 1/2 weight = 7.84 N half distance = 24.5 theta angle between vertical and wire Tan theta = 24.5/.149 theta = 89.65155 so cos theta = .00608152 T cos Theta = half the weight T = 7.84 N/.00608152 = ...
Friday, February 21, 2014 at 6:17pm by Damon

Chemistry
I posted this before and am sorry to post again and take up room but it is due this week and I'd like to understand how to get the answer (no one has responded yet): question The nuclide 38cl decays by beta emission with a half life of 40min. A sample of .40 m of H38cl is ...
Monday, July 22, 2013 at 10:10am by Nancy

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

Chemistry
time = -(half life)*ln(fraction remaining)/ln(2) = -(12.3)*(0.34)/ln(2) = 19.1 years.
Tuesday, December 7, 2010 at 8:03am by MathMate

Chem
64----> 32---> 16----->8 1 2 3 There are 3 half life. Divide 42/3 = 14 days
Wednesday, October 19, 2011 at 2:02pm by Robert

Logarithms
1.) A fossil is burned and the CO2 produced is captured. It produces 453 counts of radiation per gram. Under the same conditions atmospheric CO2 produces 19 277 counts. Calculate the age of the fossil. I have the formula: Nt = N0 e^ -t(ln2)/T Nt is the number of atoms of ...
Tuesday, September 4, 2012 at 10:24pm by Amy

College Math
A certain man spent 10% of his life in childhood and 20% of his life as a young adult at which time he married his lovely bride. Five years later his son was born. His son lived to be half the age of his father when his father died. The man died ten years after his son died. ...
Monday, September 29, 2008 at 11:03pm by Jess

Half-Lifes
The half life is given in the problem (last line you typed) of 7.2 minutes. I write a t1/2 To turn on subscript type < followed by sub followed by >. Then type the 1/2. To turn subscript off type < followed by /sub followed by >
Tuesday, April 12, 2011 at 11:24pm by DrBob222

mechanics of materials
The change in length of a steel wire under an applied load can be halved by keeping all other conditions constant but using:which of the following is correct A. a different material having a Young's modulus half that of steel B half the cross sectional area of the steel wire C...
Friday, February 22, 2013 at 6:04am by dmkp

Chemistry
HCO2H(g) CO2(g) + H2(g) The half-life for the reaction at 550 C is 24 seconds. How many seconds does it take for the formic acid concentration to decrease by 75%?
Wednesday, November 11, 2009 at 7:30am by Anonymous

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

Chemistry 212
the half life of F18 is 2.089x10^-4yrs. How long would it take (in days) for F18 to decrease to 78.71% of its initial amount?
Monday, May 10, 2010 at 1:58am by pookie

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
carbon 14 has a half life of 5715 years. If you start with a 5 gram sample of 14C, what mass is left after 15,000 years?
Tuesday, April 24, 2012 at 4:08pm by Mima

Chemistry
A fossil is found to have a C-14 level of 86% compared to living organisms. How old is the fossil?, (the half life of C14 is 5730 years).
Friday, April 27, 2012 at 9:00pm by Mima

earth science
if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days
Thursday, November 29, 2012 at 3:43pm by lan

earth science
if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days
Thursday, November 29, 2012 at 3:43pm by lan

earth science
if carbon 14 has a half life of 24 days how much would be left of 220 gram sample after 168 days
Thursday, November 29, 2012 at 3:43pm by lan

chemistry
Carbon-14 has a half-life of 5730 . In a plant fossil, you find that the has decayed to 1/32.0 of the original amount. How long ago was this plant alive?
Monday, December 3, 2012 at 1:20am by niles28

physical science
cobalt-60 has a half-life of 5.26 years, how much of a 500 gram sample will be left after 21 years
Saturday, February 16, 2013 at 3:53pm by sue moore

physical science
sodium-24 has a half life of 15 hours,how much of a 50 gram sample will be left after 60 hours
Saturday, February 16, 2013 at 8:53pm by sue moore

chemstry
How long will it take 200 mg of carbon-14 to decay to the point where only 75 mg remain if the half-life is 5770 years?
Thursday, October 31, 2013 at 10:14am by jordan

chemstry
How long will it take 200 mg of carbon-14 to decay to the point where only 75 mg remain if the half-life is 5770 years?
Thursday, October 31, 2013 at 1:02pm by jordan

physics
(a) Twice the fall time (t) from a height of h = 26 ft. The fall time t is given by (g/2)t^2 = h So, t = sqrt(2h/g)= 1.27 s Use g = 32.2 ft/s^2 2t = 2.54 s (b) Average speed is lower at the top half. That makes the time spent there longer than is is on the bottom half. (c) ...
Monday, September 10, 2012 at 3:53am by drwls

physics
The bunny is initially hopping east at 7 m/s when it first sees the fox. Over the next half second the bunny changes its velocity to west at 12 m/s and escapes. What was the bunny's average acceleration (magnitude and direction) during this half-second interval?
Thursday, October 11, 2012 at 10:25pm by Nellie

Nuclear physics
1)7Be decays with a half-life of about 53 d. It is produced in the upper atmosphere, and filters down onto the Earth's surface. If a plant leaf is detected to have 300 decays/s of 7Be, how many days do we have to wait for the decay rate to drop to 13.6/s? 2) What is the energy...
Wednesday, April 16, 2008 at 12:32pm by Sandhya

Chemistry
Not hard to find see http://en.wikipedia.org/wiki/Isotopes_of_molybdenum or the table of isotopes in 'Handbook of chemistry and physics' Mo-86 is a positron emitter with a half life of 19.6 s
Thursday, November 17, 2011 at 7:59am by Dr Russ

physics
The rubidium isotope 87Rb is a β emitter that has a half-life of 4.9 x 1010 y that decays into 87Sr. It is used to determine the age of rocks and fossils. Rocks containing the fossils of early animal have a ratio of 87Sr to 87Rb of 0.004. Assuming that there was no 87Sr ...
Wednesday, October 10, 2012 at 8:40pm by Anonymous

Chemisrty
An intravenous line provides a continuous flow of drug directly into the blood. Assuming no initial drug in the blood, the amount of drug in the blood t hours after the dosing begins in m(t) - (a/k)(1-e^-kt), for t (=>)0, where k is the rate constant (again related to half ...
Tuesday, April 17, 2012 at 2:10pm by Rach

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

Chem
"But the half filled rule, and the one you apparently used to fill the s half way and the p orbitals half way, ARE FOR THE SAME ORBITAL" So the 2S and 2P are both in the second orbital so therefore there is no electron promotion?
Tuesday, July 7, 2009 at 3:11pm by Lena

mechanics of materials
Select the correct answer.The change in length of a steel wire under an applied load can be halved by keeping all other conditions constant but using: A. A different material having a Young's modulus half that of steel B half the cross sectional area of the steel wire C half ...
Thursday, February 21, 2013 at 5:34pm by dmkp

Physics
A thin, uniform rod is hinged at its midpoint. To begin with, one half of the rod is bent upward and is perpendicular to the other half. This bent object is rotating at an angular velocity of 6.8 rad/s about an axis that is perpendicular to the left end of the rod and parallel...
Saturday, November 17, 2012 at 7:45pm by greg

Chemistry
How much time in years (assume a 365 day yr) would it take for a 1.6678g sample of 239Np to decay to a mass of 0.8671g if it has a half life of 2.030*10^5s
Friday, May 6, 2011 at 11:20am by Jay

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
In solution, hypochlorite ion is known to decompose with a second-order rate law. If [ClO-]0 = 0.0570 M and k = 2.06x10-4 M-1min-1, calculate the half-life for this reaction 2ClO-  2Cl- + O2.
Thursday, September 6, 2012 at 8:37pm by Amber

Chemistry/math
Cesium-137 has a half-life of 30 years. Suppose a lab stored a 30-mCi sample n 1973. How much will be left in 2063?
Wednesday, April 15, 2009 at 4:28pm by Angie

math
how to compute this problem? a certain element has a half life of 12 years. if there were 1000 milligrams originally, find the remaining amount after 20 years?
Wednesday, January 12, 2011 at 8:01am by diane

chemistry
a sample of a radioisotope had a mass of 100.0 grams. After exactly 24 days, 6.25 grams remained. The half life of the isotope is _________
Friday, June 3, 2011 at 7:57am by rick

algebra
The half-life of plutonium-234 is 9 hours. If 40 milligrams is present now, how much will be present in 4 days? (Round your answer to three decimal places.)
Sunday, November 20, 2011 at 10:27pm by meghan

chemistry
If something originally contained 32.0 g of Po-210, which has a half-life of 10.5 minutes, and was now 73.5 minutes old, how many grams would be left?
Monday, May 13, 2013 at 8:57pm by Mary

physics
use the doppler formula, moving observer. I am not certain what is meant by the As you drive away... I suspect the total doppler change 147hz from high to low, meaning the max dopper change was half that on approaching, and half when going away.
Monday, January 28, 2013 at 6:51am by bobpursley

physics
bar subjected to gravity load (two segments) the bar in the fig has constant cross sectional area A .the top half of the bar is made of material with mass density and youngs module, the bottom half of the bar made of density and young module total length of bar is 2 when bar ...
Wednesday, May 1, 2013 at 4:49am by mehwish

physics
bar subjected to gravity load (two segments) the bar in the fig has constant cross sectional area A .the top half of the bar is made of material with mass density and youngs module, the bottom half of the bar made of density and young module total length of bar is 2 when bar ...
Wednesday, May 1, 2013 at 4:50am by mehwish

physics
bar subjected to gravity load (two segments) the bar in the fig has constant cross sectional area A .the top half of the bar is made of material with mass density and youngs module, the bottom half of the bar made of density and young module total length of bar is 2 when bar ...
Wednesday, May 1, 2013 at 4:50am by mehwish

Quick Math
I have a question: How would you solve this? a dozen dozen apples at half a dozen dimes a dozen? In this cause is dozen 12? And half a dozen dimes in 60 cents? So half a dozen dozen is 144/2 so thats 72 correct? yes, half a dozen dozen is 144/2 = 72 but I don't know what that ...
Tuesday, December 5, 2006 at 5:56pm by Gina

social
Yes. I think everlasting life was another appeal. The prospect of life in heaven made it easier to bear the hardships in life.
Sunday, December 11, 2011 at 4:44pm by Ms. Sue

physics
The frequency of each of the two waves is f = 10/2 = 5 Hz and wavelength is V/f = 4 meters. The distance between nodes of a standing wave is half a wavelengh (2 meters). There are five half-waves between the second and seventh node. Put it all tgether for the answer.
Sunday, February 1, 2009 at 10:34pm by drwls

physics
The frequency of each of the two waves is f = 10/2 = 5 Hz and wavelength is V/f = 4 meters. The distance between nodes of a standing wave is half a wavelengh (2 meters). There are five half-waves between the second and seventh node. Put it all tgether for the answer.
Sunday, February 1, 2009 at 10:34pm by drwls

Intergrated physics and chemistry
A 52.0-kilogram skateboarder does a trick on a half-pipe. During the trick, he reaches a speed of 8.90 m/s. The radius of the half-pipe ramp is 3.00 meters. What is the minimum centripetal force necessary to keep the skater on the ramp?
Thursday, January 26, 2012 at 3:32pm by Micah

History
What factors shaped the move from colonial, country life to modern, urban life? What was urban city life like during the rise of urbanization? How was it different or similar to modern urban life?
Monday, January 4, 2010 at 2:16pm by ggift

Physics
Let N be the number of half-lives. (1/2)^N = 10^-4 N log(0.5) = log(10^-4) -0.30103 N = -4 N = 13.29 half-lives
Friday, July 27, 2012 at 5:17pm by drwls

adult education
How will your life experiences prove beneficial as you move through your degree program? Briefly describe two life experiences and illustrate how each will be useful as you pursue academic goals. How can you reject the negative influences in your life and benefit from the ...
Sunday, November 7, 2010 at 4:35pm by tee

physics
A thermal neutron beam of intensity 1 to the power 11, neutrons/sec is directed for 2 days into a cavity in a block of cobalt initially composed entirely of the stable isotope Cobalt 59. The neutrons are all captured, producing cobalt 60 nuclei which are radioactive with a ...
Saturday, November 2, 2013 at 3:29pm by Ryan

Physics
Vavg = (V1 + V2) / 2, V1 = velocity for 1st half of trip, V2 = velocity for 2nd half of trip, 2.5 m/s = (1 m/s + V2) / 2, Cross multiply: 1 + V2 = 5, V2 = 5 - 1 = 4 m/s = 9 mi/hr. She will have to average 4 m/s or 9 mi/hr for the 2nd half of trip. Quite a task! Solve for V2:
Monday, September 13, 2010 at 7:13pm by Henry

MATH
Well technically both girls are right Lynn is right when it comes to portions sizes of different halves. But Tara is right when it comes to just half because a half is a half no matter what.
Monday, January 25, 2010 at 5:43pm by Gillian

chemistry math
linen scrolls contain 80.9% of Carbon-14. how old are the scrolls if the half-life for deacy is 5.73X10^3?? plz tell me what type of equation to use.
Wednesday, October 15, 2008 at 8:19pm by ronny

Chemistry
Since the problem asks for the half-life in minutes, I wonder why you converted to seconds then back to minutes? Have you tried leaving the rate in min? t(1/2) = 0.693/6.2 x 10^-4 = ??
Tuesday, November 10, 2009 at 1:36pm by DrBob222

Calculus
Radius decays at a rate of that is proportional to its mass, and has a half-life of 1590 years. If 20 g of radium is present initially, how long will it take for 90% of this mass to decay?
Thursday, June 17, 2010 at 2:29pm by Anonymous

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

Chemistry
k = 0.693/t1/2 Look up the value of half-life in your text or notes (or tables on the Internet). Then ln(No/N) = kt No = 88 g N = 11 g k = from above. Solve for t.
Sunday, October 6, 2013 at 7:47pm by DrBob222

college algebra
An isotope of lead, 201Pb, has a half-life of 8.4 hours. How many hours ago was there 40% more of the substance? (Round your answer to one decimal place.) ____hr
Sunday, November 17, 2013 at 4:10pm by Dee

College Chemistry
How much time in years (assume a 365 day yr) would it take for a 1.6678g sample of 239Np to decay to a mass of 0.8671g if it has a half life of 2.030*10^5s
Thursday, May 5, 2011 at 9:32pm by Jude

chemistry
An isotope that emits alpha and beta radiation in addition to gamma rays, would cause much more internal cellular damage, even if its half life and intensity were similar to that of Tc-99.
Sunday, October 7, 2012 at 11:27am by GeorgeK

Chemistry
2n = No/N. No = 100 N = 1. Solve for n. I get n - 6.64 half lives which means you need 7 half lives to get to less than 1 g. Six half lives leaves 1.56 g.
Sunday, October 28, 2007 at 8:28pm by DrBob222

Chemistry
a compound decomposes with half life of 8seconds and is independent of concentration.how much time is consumed to convert the concentration of one sixteenth of its initial concentration?
Tuesday, October 23, 2012 at 1:31pm by Maria

physics
consider the spring, when compressed, with a k, compressed x distance. cut it in half. Each spring has the same force, compressed half the distance. k'=F/(x/20 or 2F/x= 2k
Thursday, December 17, 2009 at 8:38am by bobpursley

nuclear chem
i need help solving this. Can you guys show me how it's done. Radium-226 decays by alpha emission to radon-222, a noble gas.What volume of pure Radon- 222 at 23oC and 785mmHg could be obtained from 543.0 mg of radium bromide,RaBr2 in a period of 20.2 years.The half-life of ...
Sunday, August 5, 2007 at 9:01pm by kenny

Physics
The lower half of an inclined plane is rough the upper half being smooth a particle is allowed to slide from the top and is brought to rest by friction just as it reaches the bottom, find the ratio of the force of friction to the weight of the particle intermes of the ...
Monday, March 3, 2014 at 3:20pm by Ermias Abebe

Physics
The lower half of an inclined plane is rough the upper half being smooth a particle is allowed to slide from the top and is brought to rest by friction just as it reaches the bottom, find the ratio of the force of friction to the weight of the particle intermes of the ...
Monday, March 3, 2014 at 3:50pm by Ermias Abebe

Chemistry
If there is a radiation that has a half life of 10 days and we have it for 110 days, what will be the fraction of radiation left?
Sunday, November 6, 2011 at 1:59am by Jennifer

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 raidoactive iodine-123 in a sample decreases from 0.4 to 0.1 g in 26.2 hours, what is the half-life of iodine-123?
Sunday, November 14, 2010 at 2:26pm by Erin

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

help
the half-life of a radium is 1690 years is 90 grams is present now, how much will be present in 70 years
Friday, December 2, 2011 at 2:32am by Anonymous

Chemistry
What is the half-life of a 100.0 g sample of nitrogen-16 that decays to 12.5 g of nitrogen-16 in 21.6 s? Please help me!!
Tuesday, December 11, 2012 at 10:57pm by Matthew

Math
half life of a drug in the bloodstream is 14 hours. By what factor does the concentration of the drug decrease in 22 hours?
Saturday, December 14, 2013 at 7:57pm by Clare

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