Friday

July 31, 2015

July 31, 2015

Number of results: 74,742

**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 ...
*March 3, 2014 by Ermias Abebe*

**Chemistry**

A half-cell that consists of a copper wire in 1.00 M CuNO3 solution is connected by a salt bridge to a half cell containing a 1.00 M X(II) acetate solution and an electrode of metal X. The voltage of the cell is 2.00 V, with metal X as the positive electrode. Calculate the ...
*April 12, 2015 by JUNDY*

**chemistry**

use the nuclear decay equation to find out how much a 7mg sample of iodine 128 remains after 116 minutes if the half life of this isotope is 25 minutes.
*October 12, 2010 by dela*

**science**

12. Aluminum in blood plasma was shown to undergo a first order elimination reaction with a half-life of 160 days. If the initial concentration was 8.2 µg/L, how long will it take for the concentration to drop to 2.5 µg/L?
*February 13, 2011 by dan*

**math**

solve the problem. the half-life of 234U, uranium-234, is 2.52 multiplied by 105 yr. If 98.3% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?
*July 26, 2011 by juliet*

**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*

**Science**

A persistent organic pollutant is estimated to have a half-life of 30y. If 3 tonnes of the chemical exists in a polluted area today, how much of the chemical will remain after 120y.
*December 19, 2013 by Lily*

**chemistry**

If the breakdown half-life of a pesticide applied to a farmer’s field is 3.50 days, then what is the rate constant for this reaction? Assume the degradation reaction follows first order kinetics. The units are 1/d.
*February 14, 2015 by danny*

**Ethics**

Which of the following answers to the meaning of life did Tolstoy hold prior to his change of heart and mind? my answer is A a. Life has no meaning, and we must embrace that fact. b. Life's meaning is to provide comfort for oneself and one's family. c. Life's meaning is to ...
*February 18, 2014 by Annmarie*

**Chemistry**

a certain first order decomposition reaction has a half-life of 15.0 minutes. What is the rate constant for this reaction? what is the time it will take for the reaction to reach the 10% completion point?
*October 24, 2012 by Josh*

**Chemistry**

What is the half-life of sodium-24? Explain how you determined your answer. Sodium-24 decays by beta emission. Write a nuclear equation that shows the decay of sodium-24 and its products.
*May 31, 2013 by Help plz....Chloe*

**science**

1. What is the half-life of Strontium-90? Explain your answer. Honestly I don't know how to get this answer. I've looked it up and stuff, but I just found the answer not how to know what it is. A link or explanation would be greatly appreciated. Thanks.
*February 27, 2014 by Rainshine*

**physics**

We have to do a lab in physics where we research and write on real life applications of momentum, the guidelines we have are Research Assignment: Application of Momentum in Real-Life Situations Task: Choose any real-life situation where the concept of momentum is involved and ...
*March 24, 2015 by Al*

**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*

**chemistry**

so if my graph is absorbance vs time in minute, then my half life formula should give me time in minute right?
*May 17, 2010 by bme1*

**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*

**Chemistry**

The half-life for the process 238 U --> 206 Pb is 4.5*10^9 yr. A mineral sample contains 66.0 mg of 238 U and 16.0 mg of 206Pb. What is the age of the mineral?
*February 12, 2012 by gary*

**chemistry**

Nitrogen-13 has a half-life of 10 minutes. Given a starting mass of 2.00 g of nitrogen-13, how many grams will remain at the end of 30 minutes?
*June 19, 2012 by drew*

**Chemistry**

Potassium-42 has a half life of 12.4 hours. How much of an 848 g sample of potassium-42 will be left after 62.0 hours? Please help me!!
*December 11, 2012 by Cindy *

**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*

**Chemistry**

Assuming an element's half-life is 3.6 years. How much of 2 grams of the element would remain after 10.8 years?
*October 24, 2014 by Chandler*

**Chemistry**

If a 40 gram sample of radioactive isotope was present at 4pm, but a 5 gram sample remained at 4:30 pm, what is the half-life in minutes?
*December 15, 2014 by Jason*

**Science**

I need to know how much of a 2g sample of Technetium-99 would be left after 12 hours. The half life of Technetium-99 is 6 hours
*January 14, 2015 by Victoria*

**calculus**

The half-life of Radium-223 is 11.43 days. If a sample has a mass of 900 mg, find the mass (in mg) that remains after 5 days
*October 14, 2010 by Connor*

**College Algebra**

Only 34% of the carbon-14 in a wooden bowl remains. How old is the bowl? (Carbon-14 has a half-life of 5,700 years.)
*November 22, 2010 by Lexi*

**College Algebra**

Only 27% of the carbon-14 in a wooden bowl remains. How old is the bowl? (Carbon-14 has a half-life of 5,700 years.)
*December 1, 2010 by Laura Hieb*

**algebra**

11) The Half-Life of Tylenol is approximately 3 hours. If you take 1000mg, how Tylenol much is left in your body after 4 hours?
*December 9, 2010 by Mary*

**science**

If I begin with 100 atoms, how many atoms will be left of carbon 12 in 17,190 yrs if the half life of C12 is 5,730 yrs?
*April 4, 2012 by betty*

**Chemistry**

A 1.50- gas sample at 722 and 25.0 contains 7.56 radon-220 by volume. Radon-220 is an alpha-emitter with a half-life of 55.6s
*September 21, 2012 by Diamond*

**Chemistry**

A sample of charcoal is found to have only 1/8th of Carbon-14. Half-life of Carbon-14 is 5730yrs, what is the age of the charcoal?
*December 1, 2012 by Anonymous*

**integrated math**

Suppose a laboratory has a 26 g sample of polonium-210. The half-life of polonium-210 is about 138 days.?
*January 15, 2013 by sara*

**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*

**Chemistry**

The half-life of 131I is 8.021 days. What fraction of a sample of 131I remains after 24.063 days? 1/2 1/4 1/8 1/16 Please help. Thank you
*January 24, 2014 by Kiki*

**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*

**chemistry**

The half-life of oxygen-15 is 124 s. If a sample of oxygen-15 has an activity of 4800 Bq, how many minutes will elapse before it has an activity of 600 Bq?
*September 27, 2014 by Anonymous*

**calculus**

The half-life of Radium-223 is 11.43 days. If a sample has a mass of 400 mg, find the mass (in mg) that remains after 6 days
*October 14, 2014 by w*

**Math**

The half life of Uranium 230 is 20.8 days. How long would it take for 20% of Uranium 230 to decay?
*January 11, 2009 by J*

**Exponential Decay**

the half-life of carbon-11 is 20 minutes. How long will it btake for 600g of carbon-11 to decay to 30g?
*October 22, 2009 by Mark*

**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*

**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?
*November 14, 2010 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
*April 17, 2011 by Sara*

**Science**

43Lb has a half life of 42 minutes. If you start with 100 grams, how many grams will you have after 84 minutes?
*January 28, 2014 by Sabrina*

**chemistry**

If 9.00 g of _27^60 Co (half-life = 5.30 y) are allowed to decay, how many grams would be left after 1.00 y and after 10.0 y? g after 1.00 y g after 10.0 y
*April 23, 2015 by tarsa*

**Physics**

At 08:00hrs a 2.7- m-long vertical stick in air casts a shadow 1.8 m long. If the same stick is placed at 08:00hrs in air in a flat bottomed pool of salt water half the height of the stick, how long is the shadow on the floor of the pool? (For this pool, n = 1.64.) I can't get...
*May 27, 2008 by Katie*

**Chemistry**

Ba-140 has a half life of 13.0 days. What fraction of a sample of Ba-140 will remain after 39 days? A. 1/8th B. 1/16th C. 1/2th D. 1/4th
*May 23, 2010 by Charleze*

**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?
*February 1, 2011 by carlos*

**Chemistry**

Cobalt-60, which undergoes beta decay, has a half-life of 5.26 yr. How many beta particles are emitted in 190s by a 3.10mg sample of Co-60? What is the activity of the sample in Bq?
*February 12, 2012 by gary*

**Chemistry**

Cobalt-60, which undergoes beta decay, has a half-life of 5.26 yr. How many beta particles are emitted in 190s by a 3.10mg sample of Co-60? What is the activity of the sample in Bq?
*February 12, 2012 by gary*

**Chemistry**

Cobalt-60, which undergoes beta decay, has a half-life of 5.26 yr. How many beta particles are emitted in 190s by a 3.10mg sample of Co-60? What is the activity of the sample in Bq?
*February 12, 2012 by Steven*

**Chemistry**

Cobalt-60, which undergoes beta decay, has a half-life of 5.26 yr. How many beta particles are emitted in 190s by a 3.10mg sample of Co-60? What is the activity of the sample in Bq?
*February 13, 2012 by Steven*

**math**

only 5% of the carbon-14 in a small wooden bowl remains , how old is the bowl? Hint, half-life for carbon –14 us 5730 years
*April 4, 2012 by martha*

**chem**

the half life of oxygen-15 is 124 s. if a sample of oxygen-15 has an activity of 4000 Bq, how many minutes will elapse before it reaches an activity of 500Bq
*June 5, 2012 by Anonymous*

**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*

**Chemistry**

Calculate the time in which the activity of an element is reduced to 90% of its original value. The half-life period of the element is 1.4*10^10 years . Answer :- 2.13*10^9 years
*November 20, 2014 by Harsh*

**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.
*January 29, 2011 by Korina*

**Calculus **

The half-life of Kryponite-123 is 40 years. Suppose we have a 700-mg sample. Find the decay k, and the expected amount of Kryptonite left after 30 years. I need help setting this problem up.
*March 23, 2015 by Ryan kustin*

**Chem**

If compound X has a first-order half-life of 24 seconds, how long would you have to wait for only 33% of the original material to be left? Explain why not knowing original Molarity of X does not effect this problem.
*July 21, 2015 by Jessica*

**chemistry**

If C14 has a half-life of 4,000 years, what fraction will be remaining after 36,000 years?
*July 7, 2011 by g*

**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?
*July 10, 2011 by g*

**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?
*November 6, 2011 by Jennifer*

**help**

the half-life of a radium is 1690 years is 90 grams is present now, how much will be present in 70 years
*December 2, 2011 by Anonymous*

**CHEM**

An isotope has a half life of 56 days. It now has 10,000DPM/ml. What will its activity be 100 days from now?
*April 17, 2013 by Jared*

**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?
*December 14, 2013 by Clare*

**Physics**

An industrial worker accidentally inhaled a radioisotope with an activity of 0.200 kBq. The substance swallowed has a very long effective half-life and therefore the activity will not change significantly during the workerâ€™s lifetime. Every decay of the isotope releases 1.12...
*May 16, 2010 by Kirsten*

**Physics**

An industrial worker accidentally inhaled a radioisotope with an activity of 0.200 kBq. The substance swallowed has a very long effective half-life and therefore the activity will not change significantly during the workers lifetime. Every decay of the isotope releases 1.12 x ...
*May 17, 2010 by Anonymous*

**Chemistry**

Strontium-85, used for bone scans, has a half-life of 64 {\rm d}.How long will it take for the radiation level of strontium-85 to drop to \frac{1}{8} of its original level?
*April 27, 2011 by Help!!*

**Biology**

The half life of carbon 14 is 5700 years. If the carbon 14 level measured in a fossilized bone has only 1/4 of the original amount, how old in the bone?
*May 16, 2011 by Jennifer*

**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*

**Biology**

The half-life of carbon-14 is 5,700 years. If a sample originally had 26 g of carbon-14, how much would it contain after 22,800 years?
*November 19, 2013 by Emily*

**biology**

What geological process is used to explain how nearly identical animals that cannot swim, are found on continents separated by large oceans? What is the half-life of Uranium 238 and what did we use that radioisotope to date as the oldest item on Earth?
*April 21, 2012 by Anonymous*

**writing**

do you think that life on earth could become this difficult during your life time?what factor could cause to take place ?a story about that shows what life might be like in the world?
*January 1, 2013 by Eduarda*

**liteature**

In The Call of the Wild, when London writes about "what a puppet thing life is," it reflects the theme summarized in which of the following statements? A. Our lives are lived in response to our predetermined fate. B. The course of a life is determined by pure chance. C. Each ...
*April 14, 2009 by victoria*

**Literature**

In The Call of the Wild, when London writes about "what a puppet thing life is," it reflects the theme summarized in which of the following statements? A. Our lives are lived in response to our predetermined fate. B. Each life pits mercy against nature. C. Every life is based ...
*September 24, 2012 by Sara Beth*

**Chemistry**

The reaction 2B--->C + 2D is found to be zero order when run at 990 degrees C. If it takes 3.3X110^2 s for an initial concentration of B to go from 0.50 M to .20 M what is the rate constant for the reaction? what is the half life of the reaction under these conditions?
*February 29, 2008 by Lauren*

**Math**

A bone is found to have 45% of the original amount of carbon 14. If the half life of carbon is 5600 years, how old is the bone. Would I use the formula N=No e^kt?
*November 20, 2010 by Hannah*

**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*

**Chemistry**

A decomposition reaction has a rate constant of 0.0019 yr -1. ( a) What is the half-life of the reaction? ______ yr (b) How long does it take for [reactant] to reach 12.5% of its original value? ______ yr
*December 2, 2011 by Sam*

**Chemistry**

Radium-223 has a half-life of 11.4 days.Approximately how long would it take for the activity of a sample of Radium-223 to decrease to 1.00% of its initial value?
*March 1, 2013 by Michelle*

**A.P. Chemistry**

Thorium-232 undergoes alpha decay and has a half-life of 1.4 * 10^10 years. How long will it take for a 1.00mg sample of thorium-232 to be reduced to 0.5mg?
*April 25, 2013 by John*

**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*

**chemistry**

The half-life of I-131 is 8.00 days. If a medical treatment involves a dose of 400. mg of I-131, how much of the isotope remains after 48 days? 3.125 mg 6.25 mg 12.5 mg 25 mg
*December 2, 2014 by Tamera*

**science**

what is the Half-life of strontium 90. Explain your work. Okay well I already know the answer is 28yrs but I just don't know how to explain it on how I got the answer... can you guys help me please! I need this done in 30 seconds..
*January 8, 2015 by Channy-Boo*

**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*

**college algebra**

Use a calculator to help solve the problem. 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
*November 18, 2013 by Dee*

**physics**

how to i find average speed? the problem says. a driver set outa journey for the first half she drives at 30mi/h and second half 60mi/h. Find the driver's average speed?
*October 17, 2007 by Ron*

**PHYSICS **

A 5.30-g lead bullet traveling at 390 m/s is stopped by a large tree. If half the kinetic energy of the bullet is transformed into internal energy and remains with the bullet while the other half is transmitted to the tree, what is the increase in temperature of the bullet?
*November 26, 2012 by please help *

**Science HELP 2nd question**

A sample originally contained 2.5 g of rubidium 87 now contains 1.25 g. The half life of rubidium - 87 is 6 x 10 ( to the 10th) years. How old is teh sample? Is this possible? why or why not?
*February 8, 2008 by sam*

**Chemistry**

The half-life of oxygen -15 is 124 seconds. If a sample of oxygen -15 has an activity of 4000 becquerels, how many minutes will elapse before it reaches an acivity of 500 becquerels
*July 20, 2010 by Elisabeth*

**calculus**

Assume a substance has a half-life of 11 years and the initial amount is 144 grams. How much remains at the end of 5 years? How long will it be until only 30 % remains?
*September 14, 2010 by nick*

**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*

**math**

A material has a half-life of 12 hours. If initially there are 4 grams of the material, how much is present after 8 hours? I know the answer is 8/3, but how would you solve this using calculus? please help.
*November 11, 2012 by alex*

**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*

**Chemistry**

Iron -59 has a half life of 45.1 days. How old is an iron nail if the Fe-59 content is 25% that a new sample of iron? Show all calculations leading to a solution. Can you work the problem? I don't know how to solve for t!!! Please.
*May 11, 2015 by noemi/ *

**science**

A British Concorde (BC) and a French Concorde (FC) flew in opposite directions around the earth (40 000 km). The BC covered half of its flight distance at a supersonic speed of 2500 km/h and the other half at a subsonic speed of 1000 km/h. The FC spent half of its flight time ...
*February 8, 2014 by king12*

**college physics**

By immersing a crown in water its volume is 26inc^3=4.2x10^-4m^3. what would its weight be if it were pure gold? What would its weight be if its volume were half gold and half lead?
*October 1, 2012 by tiffany*

**science**

If the half-life of a 20.0g is known to be 24 minutes, how long will it take for only 5.0 grams of the sample to remain A.6 minutes B.24 minutes C.48 minutes D.96 minutes I NEED HELP!!!!
*September 25, 2013 by amor*

**Maths**

Trudy brought a large bag of wine gums to school. She gave half to the first student she met, half the remainder to the next and half of what she had left to the third student. The last 5 wine gums she ate. How many were in the packet?
*March 2, 2009 by Jessika.*