Question 1

The primary reason very large nuclei are unstable is due to

Accepted Answer

A) the cumulative repulsive force amongst the protons. 
B) the cumulative attractive force between the protons and the orbiting electrons. 
C) the repulsive force between the neutrons and the protons. 
A) the cumulative repulsive force amongst the protons. 
B) the cumulative attractive force between the protons and the orbiting electrons. 
C) the repulsive force between the neutrons and the protons.

Question 2

Two radioactive nuclides X and Y both decay to stable products.The half-life of X is about a day,while that of Y is about a week.Suppose a radioactive sample consists of a mixture of these two nuclides.If the mixture is such that the activities arising from X and Y are initially equal,then a few days later the activity of the sample will be due

Accepted Answer

A) predominantly to nuclide Y. 
B) predominantly to nuclide X. 
C) entirely to nuclide Y. 
D) to nuclides X and Y equally. 
A) predominantly to nuclide Y. 
B) predominantly to nuclide X. 
C) entirely to nuclide Y. 
D) to nuclides X and Y equally.

Question 3

An archaeologist finds the 14C in a sample of 3.10 g of material to be decaying at 107 counts per second.A modern 1.00-g sample of the same material decays at 151 counts per second.The half-life of 14C is 5730 years.How old is the sample?

Accepted Answer

A) 12,200 years 
B) 8460 years 
C) 25,100 years 
D) 12,600 years 
A) 12,200 years 
B) 8460 years 
C) 25,100 years 
D) 12,600 years

Question 4

A nuclear bomb explosion results in a mass decrease of about 2.10 g between the initial and the final ingredients.How much energy is released?

Accepted Answer

A) 1.89 × 1014 J 
B) 6.30 × 105 J 
C) 1.89 × 1013 J 
D) 2.25 × 1012 J 
A) 1.89 × 1014 J 
B) 6.30 × 105 J 
C) 1.89 × 1013 J 
D) 2.25 × 1012 J

Question 5

In a head-on collision,an alpha particle (Z = 2)of energy 8.20 MeV bounces straight back from a nucleus of charge 80.0 e.How close were the centers of the objects at closest approach?

Accepted Answer

A) 2.81 × 10-14 m 
B) 3.39 × 10-12 m 
C) 6.56 × 10-15 m 
D) 2.17 × 10-14 m 
A) 2.81 × 10-14 m 
B) 3.39 × 10-12 m 
C) 6.56 × 10-15 m 
D) 2.17 × 10-14 m

Question 6

The material used in nuclear bombs is 239Pu,with a half-life of about 20,000 years.How long must we wait for a buried stockpile of this substance to decay to 4% of its original 239Pu mass?

Accepted Answer

A) 93 thousand years 
B) 64 thousand years 
C) 45 thousand years 
D) 0.80000001 thousand years 
A) 93 thousand years 
B) 64 thousand years 
C) 45 thousand years 
D) 0.80000001 thousand years

Question 7

A stable nucleus contains many protons very close to each other,all positively charged.Why do the protons not fly apart due to mutual Coulomb repulsion?

Accepted Answer

A) Attractive nuclear forces in the nucleus counteract the effect of the Coulomb forces. 
B) There are an equal number of electrons in the nucleus that neutralize the protons. 
C) The neutrons in the nucleus shield the protons from each other. 
D) The Coulomb force does not operate within nuclei. 
A) Attractive nuclear forces in the nucleus counteract the effect of the Coulomb forces. 
B) There are an equal number of electrons in the nucleus that neutralize the protons. 
C) The neutrons in the nucleus shield the protons from each other. 
D) The Coulomb force does not operate within nuclei.

Question 8

Today,uranium contains 0.72% 235U (half-life = 0.70 billion years)and 99.28% 238U (half-life = 4.5 billion years).At a time 1.9 billion years ago,what was the fraction of 235U in uranium?

Accepted Answer

A) 3.53% 
B) 4.72% 
C) 4.90% 
D) 6.75% 
A) 3.53% 
B) 4.72% 
C) 4.90% 
D) 6.75%

Question 9

Stable nuclei have equal numbers of protons and neutrons.

Accepted Answer

A) True 
 B)False

Question 10

Suppose the half-life of some element is 2 days.If you purchase 10 grams of the element (which was produced in a laboratory 4 days ago),how much of this element would you have 3 days after you purchased it?

Accepted Answer

A) more than 2.5 grams but less than 5 grams 
B) 2.5 grams 
C) more than 1.25 grams but less than 2.5 grams 
D) 1.25 grams 
E) less than 1.25 grams 
A) more than 2.5 grams but less than 5 grams 
B) 2.5 grams 
C) more than 1.25 grams but less than 2.5 grams 
D) 1.25 grams 
E) less than 1.25 grams

Question 11

Which of the following is not true of the nuclear force?

Accepted Answer

A) The nuclear force has a short range,of the order of nuclear dimensions. 
B) For two protons in close proximity,the nuclear force and the electric force have comparable magnitudes. 
C) The nuclear force does not depend on charge. 
D) A nucleon in a large nucleus interacts via the nuclear force only with nearby nucleons,not with ones far away in the nucleus. 
E) The nuclear force favors binding of pairs of protons or neutrons with opposite spin angular momenta. 
A) The nuclear force has a short range,of the order of nuclear dimensions. 
B) For two protons in close proximity,the nuclear force and the electric force have comparable magnitudes. 
C) The nuclear force does not depend on charge. 
D) A nucleon in a large nucleus interacts via the nuclear force only with nearby nucleons,not with ones far away in the nucleus. 
E) The nuclear force favors binding of pairs of protons or neutrons with opposite spin angular momenta.

Question 12

A positron (or antielectron)is made to stop in a sample of matter.Soon after,how many gamma rays are observed with what energy each?

Accepted Answer

A) two,0.511 MeV each 
B) one,0.511 MeV 
C) none 
D) two,13.6 eV each 
E) one,13.6 eV 
A) two,0.511 MeV each 
B) one,0.511 MeV 
C) none 
D) two,13.6 eV each 
E) one,13.6 eV

Question 13

A radioactive nuclide of atomic number Z emits an alpha particle and the daughter nucleus then emits a beta particle.What is the atomic number of the resulting nuclide?

Accepted Answer

A) Z-1 
B) Z+1 
C) Z-2 
D) Z-3 
A) Z-1 
B) Z+1 
C) Z-2 
D) Z-3

Question 14

A hospital patient has been given 131I (half-life = 8.04 days),which decays at 4.2 times the acceptable level for exposure to the general public.How long must the patient wait to reach the acceptable level? Assume that the material merely decays and is not excreted.

Accepted Answer

A) 17 days 
B) 12 days 
C) 8.0 days 
D) 7.2 days 
A) 17 days 
B) 12 days 
C) 8.0 days 
D) 7.2 days

Question 15

What mass of 14C (half-life = 5730 years)do you need to provide a decay rate of 280.0 Bq?

Accepted Answer

A) 1.70 × 10-12 kg 
B) 5.38 × 10-19 kg 
C) 3.84 × 10-20 kg 
D) 8.68 × 10-13 kg 
A) 1.70 × 10-12 kg 
B) 5.38 × 10-19 kg 
C) 3.84 × 10-20 kg 
D) 8.68 × 10-13 kg

Question 16

If half of a radioactive substance decays in the first 10 s,the other half will decay in the next 10 s.

Accepted Answer

A) True 
 B)False

Question 17

The binding energy per nucleon increases steadily with the mass number of the nucleus.

Accepted Answer

A) True 
 B)False

Question 18

The following masses are known:   1.008665 u   1.007825 u   226.025403 u The binding energy of   ,in MeV,is closest to:

Accepted Answer

A) 1700 
B) 1900 
C) 2100 
D) 2300 
E) 2500 
A) 1700 
B) 1900 
C) 2100 
D) 2300 
E) 2500

Question 19

The maximum permissible workday dose for occupational exposure to radiation is 11 mrem.A 77 kg laboratory technician absorbs 2.3 mJ of 0.5 MeV gamma rays in a work day.The relative biological efficiency (RBE)for gamma rays is 1.00.The number of gamma-ray photons absorbed by the technician in a workday is closest to:

Accepted Answer

A) 3 × 1010 
B) 3 × 109 
C) 3 × 108 
D) 1 × 109 
E) 1 × 108 
A) 3 × 1010 
B) 3 × 109 
C) 3 × 108 
D) 1 × 109 
E) 1 × 108

Question 20

If a 20 kg brick is made entirely of radioactive atoms of half-life 5 days,at the end of 5 days this brick will have a mass of 10 kg.

Accepted Answer

A) True 
 B)False

Exam 30: Nuclear Physics

The primary reason very large nuclei are unstable is due to

An archaeologist finds the 14C in a sample of 3.10 g of material to be decaying at 107 counts per second.A modern 1.00-g sample of the same material decays at 151 counts per second.The half-life of 14C is 5730 years.How old is the sample?

A nuclear bomb explosion results in a mass decrease of about 2.10 g between the initial and the final ingredients.How much energy is released?

In a head-on collision,an alpha particle (Z = 2)of energy 8.20 MeV bounces straight back from a nucleus of charge 80.0 e.How close were the centers of the objects at closest approach?

The material used in nuclear bombs is 239Pu,with a half-life of about 20,000 years.How long must we wait for a buried stockpile of this substance to decay to 4% of its original 239Pu mass?

A stable nucleus contains many protons very close to each other,all positively charged.Why do the protons not fly apart due to mutual Coulomb repulsion?

Today,uranium contains 0.72% 235U (half-life = 0.70 billion years)and 99.28% 238U (half-life = 4.5 billion years).At a time 1.9 billion years ago,what was the fraction of 235U in uranium?

Stable nuclei have equal numbers of protons and neutrons.

Suppose the half-life of some element is 2 days.If you purchase 10 grams of the element (which was produced in a laboratory 4 days ago),how much of this element would you have 3 days after you purchased it?

Which of the following is not true of the nuclear force?

A positron (or antielectron)is made to stop in a sample of matter.Soon after,how many gamma rays are observed with what energy each?

A radioactive nuclide of atomic number Z emits an alpha particle and the daughter nucleus then emits a beta particle.What is the atomic number of the resulting nuclide?

A hospital patient has been given 131I (half-life = 8.04 days),which decays at 4.2 times the acceptable level for exposure to the general public.How long must the patient wait to reach the acceptable level? Assume that the material merely decays and is not excreted.

What mass of 14C (half-life = 5730 years)do you need to provide a decay rate of 280.0 Bq?

If half of a radioactive substance decays in the first 10 s,the other half will decay in the next 10 s.

The binding energy per nucleon increases steadily with the mass number of the nucleus.

The following masses are known: 1.008665 u 1.007825 u 226.025403 u The binding energy of ,in MeV,is closest to:

If a 20 kg brick is made entirely of radioactive atoms of half-life 5 days,at the end of 5 days this brick will have a mass of 10 kg.

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Using Energy

Thermal Properties of Matter

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Electric Fields and Forces

Electric Potential

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An archaeologist finds the ¹⁴C in a sample of 3.10 g of material to be decaying at 107 counts per second.A modern 1.00-g sample of the same material decays at 151 counts per second.The half-life of ¹⁴C is 5730 years.How old is the sample?

The material used in nuclear bombs is ²³⁹Pu,with a half-life of about 20,000 years.How long must we wait for a buried stockpile of this substance to decay to 4% of its original ²³⁹Pu mass?

Today,uranium contains 0.72% ²³⁵U (half-life = 0.70 billion years)and 99.28% ²³⁸U (half-life = 4.5 billion years).At a time 1.9 billion years ago,what was the fraction of ²³⁵U in uranium?

A hospital patient has been given ¹³¹I (half-life = 8.04 days),which decays at 4.2 times the acceptable level for exposure to the general public.How long must the patient wait to reach the acceptable level? Assume that the material merely decays and is not excreted.

What mass of ¹⁴C (half-life = 5730 years)do you need to provide a decay rate of 280.0 Bq?