Tuesday

February 21, 2017
Number of results: 86,080

**algebra**

The half-life of 234U, uranium-234, is 2.52 105 yr. If 97.7% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?

*January 28, 2012 by Anonymous*

**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 2**

For the fist order reaction A <-> B, calculate the t1/2(half life) and k(rate constant) and also fill in the blanks. A-Concetration t-time 20 0 10 ? 5 40 sec 3 ? ? 500 sec t1/2=? k=?

*March 3, 2014 by Ivan*

**Chemistry 2**

For the fist order reaction A <-> B, calculate the t1/2(half life) and k(rate constant) and also fill in the blanks. A-Concetration t-time 20 0 10 ? 5 40 sec 3 ? ? 500 sec t1/2=? k=?

*March 3, 2014 by Ivan*

**Chemistry**

A first-order reaction has a half-life of 26.4 seconds. How long does it take for the concentration of the reactant in the reaction to fall to one-eighth of its initial value?

*February 14, 2016 by Student*

**Math**

A fossilized leaf contains 21% of its normal amount of carbon 14. How old is the fossil (to the nearest year)? Use 5600 years as the half-life of carbon 14.

*August 3, 2016 by james*

**Math**

Suppose that the half-life of a substance is 250 yrs. .If there were initially 100 g of substance .How much will remain after 500 years??with solution please

*August 8, 2016 by Queen*

**physics**

Calculate the maximum height using the initial speed, half-time, and angle. The initial speeed is 18m/s, half time is 1.8, and the angle is 75. And how is this written out to solve.

*January 23, 2011 by Anonymous*

**mechanics**

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 the length of steel wire D ...

*February 24, 2013 by dmkp*

**Chemistry**

If 100.0 g of carbon-14 decays until only 25.0 g of carbon is left after 11,460 y, what is the half-life of carbon-14?

*December 11, 2012 by Jacob*

**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

*November 17, 2010 by carla*

**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?

*October 11, 2012 by Nellie*

**Chemistry**

I don't know the correct answer that's what i have to find. for the first part here is my work..... 6.2e-4/min=0.0372seconds half life: t_1/2=0.693/0.372s =18.6sec*1min/60sec=0.310min (which is not right!)

*November 10, 2009 by Dena*

**chemistry**

follows first-order kinetics and has an activation energy of 244 kJ mol-1. At 684 K, k = 0.00000508 s-1. What is the half-life (min) for this reaction at 427 °C ? Round your answer to 3 significant figures. I really don't know what to do

*November 19, 2010 by bobjahng2*

**Chemistry**

The half-life for the first-order conversion of A to B is 56.5 hours. How long does it take for the concentration of A to decrease to 10.0% of its original amount? Our professor has given us the answer - 188hr but I am not entirely sure how he got it.

*February 23, 2014 by Kristen*

**chemistry**

A 7.500-mg sample of chromium-55 is analyzed after 14.0 min. and found to contain 0.469 mg of chromium-55. what is the half-life of chromium-55?

*November 2, 2008 by Jasmine08*

**chemistry**

a 7.500-mg sample of chromium-55 is analyzed after 14.0 min and found to contain 0.469 mg of chromium-55. what is the half-life of chromium-55

*February 8, 2012 by lisa*

**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 ...

*November 7, 2010 by tee*

**math**

The half-life of 234U, uranium-234, is 2.52 multiplied by 105 yr. If 97.7% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?

*July 17, 2011 by Anonymous*

**math**

The half-life of 234U, uranium-234, is 2.52 multiplied by 105 yr. If 97.4% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?

*July 26, 2011 by Anonymous*

**algebra**

The half-life of 234U, uranium-234, is 2.52 multiplied by 105 yr. If 98.8% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?

*July 27, 2011 by Anonymous*

**algebra**

The half-life of 234U, uranium-234, is 2.52 multiplied by 105 yr. If 98.8% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?

*July 27, 2011 by Anonymous*

**algebra**

The half-life of 234U, uranium-234, is 2.52 multiplied by 105 yr. If 98.6% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?

*July 27, 2011 by Anonymous*

**math**

The half-life of 234U, uranium-234, is 2.52 multiplied by 105 yr. If 98.7% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed? yr

*October 20, 2011 by Anonymous*

**uncc**

the half-life of 234U, uranium-234, is 2.52 x 10^5yr. If 98.5% of thee uranium in the original sample is present, what length of time (to the nearest thousand years) has elasped

*October 25, 2011 by ellen*

**pre algebra**

The half-life of 234U, uranium-234, is 2.52 105 yr. If 98.6% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?

*April 29, 2012 by Anonymous*

**ALGEBRA**

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? =

*June 14, 2012 by Urgen please help*

**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*

**MATH104**

he half-life of 234U, uranium-234, is 2.52 multiplied by 105 yr. If 97.5% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed? yr

*December 18, 2012 by ABDALLA*

**chemistry**

Strontium-90 decays through the emission of beta particles. It has a half-life of 29 years. How long does it take for 80% of a sample of strontium-90 to decay? Show process of how you got this

*January 10, 2013 by Urgent Help*

**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

*November 17, 2013 by Dee*

**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 ...

*October 10, 2012 by Anonymous*

**maths lit, geography, life science, history, life orientation, english, tswana**

what can I do with my life with all this subjects that I studied?.

*July 18, 2014 by Ernest Mmutlana*

**physics**

• If you use a cart with half the mass, you reach _______final speed. • If you use half the force, you reach ______ final speed. • If you push twice as long, you cover _______ distance during pushing. • If you use a cart with half the mass, you cover_______ distance ...

*February 17, 2014 by Ted*

**chemistry**

You have a compound that is subject to decay. If you originally started with 80 g of the compound and you ended up with 5 grams 30 days later, what is the half-life of the compound?

*December 5, 2011 by Anonymous*

**abdul kabir**

the half life of an element is 5 days. if we have 10gram of the element initially. what is the mass of the element after 5days and 10days

*March 1, 2016 by oyedotun*

**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?

*January 26, 2012 by Micah*

**math**

half of a gallon is a half gallon. half of a half gallon is a quart. half of a quart is a pint. half of a pint is a cup. a cup is what fraction of a quart? Is the answer 1/4?

*February 27, 2011 by Trevor*

**physics**

the mass density of a mixture of ethyl alcohol and water is 950kg/m^3. is the mixture mostly water, alcohol, or about half and half. What is your reasoning?

*October 1, 2012 by tiffany*

**Physics**

Calculate the maximum height using the initial speed, half-time, and angle. The initial speeed is 18m/s, half time is 1.8, and the angle is 75

*April 13, 2015 by Jennifer*

**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...

*February 22, 2013 by dmkp*

**math**

If a hen and a half can lay an egg and a half in a day and a half, then how much time is needed for three hens to lay three eggs?

*February 21, 2017 by Sam*

**Probablity**

The life time of a certain kind of batteries has a mean life of 400 hours and standard deviation as 45 hours. Assuming the distribution of life to be normal, find i) the percentage of batteries with a life time of atleast 470 hours. Ii) Out of 10000 batteries how many ...

*October 1, 2015 by Kruti*

**shakespeare**

places in his life can it be where he was born what else conflicts in his life idk women in his life anne hathaway his wife men in his life can it be his fayher and the ppl he owrked with and his publisher children in his life susanna hamnet and judith mistakes he made idk ...

*April 22, 2014 by Reina B.*

**physics**

A car moves a distance of 200 km. It covers the first half of the distance at speed 40 km/h and second half of the distance by speed v. The average speed is 48 km/h. Find the value of v

*November 30, 2012 by maihul*

**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?

*January 4, 2010 by ggift*

**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 ...

*February 21, 2013 by dmkp*

**AP Chem ---**

Iron-59 has a half-life of 45.1 days. How old is an iron nail if the Fe-59 content is 25% that of a new sample of iron? Please show the calculating so I can learn to do it.

*May 22, 2015 by Dani*

**AP Chem ---**

Iron-59 has a half-life of 45.1 days. How old is an iron nail if the Fe-59 content is 25% that of a new iron sample? Please show the calculating so I can learn to do it.

*May 22, 2015 by Dani*

**Calculus**

Skeletal remains had lost 81% of the C-14 they originally contained. Determine the approximate age of the bones. (Assume the half life of carbon-14 is 5730 years. Round your answer to the nearest whole number.) yr

*July 12, 2013 by Anonymous*

**calculus**

Skeletal remains had lost 70% of the C-14 they originally contained. Determine the approximate age of the bones. (Assume the half life of carbon-14 is 5730 years. Round your answer to the nearest whole number.)

*March 2, 2014 by angie*

**Math**

Skeletal remains had lost 84% of the C-14 they originally contained. Determine the approximate age of the bones. (Assume the half life of carbon-14 is 5730 years. Round your answer to the nearest whole number.)

*April 5, 2014 by Vanessa*

**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...

*November 17, 2012 by greg*

**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 7.1 rad/s about an axis that is perpendicular to the left end of the rod and parallel...

*April 8, 2014 by Alex*

**Chemistry**

I need help with the following problem: A fabric remnant from a burial site had a 14 C:12 C ratio of 0.838 of the original value. How old is the fabric? (half-life of 14 C = 5370 years)

*April 29, 2009 by Sophie*

**math**

How long will it take a given quantity of carbon-14 to lose 99.9% of its radioactivity if the half life is 5730 years? The formula I have been given is Q=ae^rt This is using log and ln functions.

*April 25, 2011 by Niki*

**Algebra 2**

A 14 gram sample of a substance that's used to preserve fruit and vegetables has a k-value of 0.1092. Find the substance's half-life, in days. Round your answer to the nearest tenth.

*May 7, 2013 by Tristan*

**MATHS**

experiments show that radium disintegrates at a rate proportional to the amount of radium present at the moment . if half life is 1590 years what percentage will disappear in one year?

*September 26, 2014 by NOEL*

**MATHS**

please help me ...Experiments show that radium at rate proportional to the amount of radium present at the moment . if half life is 1590 years what percentage will disappear in one year ??

*September 26, 2014 by NOEL*

**math**

If a hen and a half lay an egg and a half in a day and a half, how many hens are needed to lay a dozen eggs in one day?

*November 28, 2007 by New Girl 102*

**English**

In “Wave,” Dale Wisely characterizes water as an element that a. gives life b. takes life c. gives and takes life d. is life

*October 26, 2015 by Kaai97*

**English**

In “Wave,” Dale Wisely characterizes water as an element that a. gives life*** b. takes life c. gives and takes life d. is life

*October 26, 2015 by Kaai97*

**Physics 2**

Calculate the maximum height using the initial speed, half-time, and angle. The initial speeed is 9.8m/s, half time is 1.8, and the angle is 75.

*April 13, 2015 by Jennifer*

**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 ...

*May 1, 2013 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 ...

*May 1, 2013 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 ...

*May 1, 2013 by mehwish*

**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?

*October 23, 2012 by Maria*

**Chemistry 2**

For a second order reaction A <--> B, calculate the t1/2 (half life) and the k(constant) and also fill in the blanks. A (concentration) t(time) 20 0 sec 10 ? 5 40 sec 3 ? ? 200 sec t1/2=? k=?

*March 3, 2014 by Ivan*

**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 of a new sample of iron? Show all calculations leading to a solution.

*May 8, 2015 by Gloria*

**chemistry**

Use the following steps to balance the redox reaction below: Mg + Au+ Mg2+ + Au -Write the oxidation and reduction half-reactions. Make sure each half-reaction is balanced for number of atoms and charge. -Multiply each half-reaction by the correct number, in order to balance ...

*February 8, 2012 by Adrian*

**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*

**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*

**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*

**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**

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*

**Chemistry**

The strontium-87 isotopes stores in the body and decays by the process shown below. The half-life is 2.80hr. Suppose that 0.766 millicuries got into the body. How many mc will remain after 8.40 hr?

*September 27, 2015 by Morgan*

**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**

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**

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*

**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*

**chemistry**

The radioactive isotope, phosphorus-32, has a half-life of 14.26 days. How much phosphorus-32 will remain after 60 days? Please help.

*September 3, 2015 by Ken*

**Algebra**

A collection of schmutz decays according to the equation y=ae^-0.0358t where t is in days. Find the half life of this schmutz collection.

*February 17, 2016 by Vero*

**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*