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- Half-life and activity
To obtain the most precise value of BE from the equation
, we should take into account the binding energy of the electrons in the neutral atoms. Will doing this produce a larger or smaller value for BE? Why is this effect usually negligible?
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Problems&Exercises
Data from the appendices and the periodic table may be needed for these problems.
An old campfire is uncovered during an archaeological dig. Its charcoal is found to contain less than 1/1000 the normal amount of
. Estimate the minimum age of the charcoal, noting that
.
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A
source is labeled 4.00 mCi, but its present activity is found to be
Bq. (a) What is the present activity in mCi? (b) How long ago did it actually have a 4.00-mCi activity?
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(a) Calculate the activity
in curies of 1.00 g of
. (b) Discuss why your answer is not exactly 1.00 Ci, given that the curie was originally supposed to be exactly the activity of a gram of radium.
(a) 0.988 Ci
(b) The half-life of
is now better known.
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Show that the activity of the
in 1.00 g of
found in living tissue is 0.250 Bq.
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Mantles for gas lanterns contain thorium, because it forms an oxide that can survive being heated to incandescence for long periods of time. Natural thorium is almost 100%
, with a half-life of
. If an average lantern mantle contains 300 mg of thorium, what is its activity?
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Cow’s milk produced near nuclear reactors can be tested for as little as 1.00 pCi of
per liter, to check for possible reactor leakage. What mass of
has this activity?
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(a) Natural potassium contains
, which has a half-life of
y. What mass of
in a person would have a decay rate of 4140 Bq? (b) What is the fraction of
in natural potassium, given that the person has 140 g in his body? (These numbers are typical for a 70-kg adult.)
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There is more than one isotope of natural uranium. If a researcher isolates 1.00 mg of the relatively scarce
and finds this mass to have an activity of 80.0 Bq, what is its half-life in years?
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has one of the longest known radioactive half-lives. In a difficult experiment, a researcher found that the activity of 1.00 kg of
is 1.75 Bq. What is the half-life in years?
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You can sometimes find deep red crystal vases in antique stores, called uranium glass because their color was produced by doping the glass with uranium. Look up the natural isotopes of uranium and their half-lives, and calculate the activity of such a vase assuming it has 2.00 g of uranium in it. Neglect the activity of any daughter nuclides.
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A tree falls in a forest. How many years must pass before the
activity in 1.00 g of the tree’s carbon drops to 1.00 decay per hour?
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A 5000-Ci
source used for cancer therapy is considered too weak to be useful when its activity falls to 3500 Ci. How long after its manufacture does this happen?
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Questions & Answers
A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what are the types of wave
Maurice
fine, how about you?
Mohammed
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
Who can show me the full solution in this problem?
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Source:
OpenStax, College physics for ap® courses. OpenStax CNX. Nov 04, 2016 Download for free at https://legacy.cnx.org/content/col11844/1.14
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