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NEET UG Nuclei — practice questions — page 4

Explore 102 free Nuclei questions in NEET UG Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Nuclei questions and exercises with answers

Showing questions 91–102 of 102.

About how high is the Coulomb barrier for two protons to fuse?Read the answer and worked solution →Average protons would cross the fusion barrier at about what temperature?Read the answer and worked solution →What is the approximate temperature of the sun's interior?Read the answer and worked solution →Net energy released when four hydrogen atoms form one helium atom in the sun?Read the answer and worked solution →At about 10^8 K in a star's core, helium nuclei fuse into what?Read the answer and worked solution →When its hydrogen runs out, the sun's outer envelope will expand into what?Read the answer and worked solution →Peaks in binding energy per nucleon at He-4 and O-16 suggest what?Read the answer and worked solution →About what neutron to proton ratio do stable heavy nuclei need?Read the answer and worked solution →When an electron meets a positron, they annihilate into what?Read the answer and worked solution →Q-value of a nuclear process equals which difference?Read the answer and worked solution →What is the SI unit of the activity of a radioactive sample?Read the answer and worked solution →Mean life of a radioactive sample is the time for its nuclei to fall to what?Read the answer and worked solution →

Worked practice questions

About how high is the Coulomb barrier for two protons to fuse?

  1. About 40 MeV
  2. About 4 eV
  3. About 4 keV
  4. About 400 keV
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Correct answer: D. About 400 keV

Two protons must overcome a Coulomb barrier of roughly 400 keV before the nuclear force acts.

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Average protons would cross the fusion barrier at about what temperature?

  1. About 3 x 10^9 K
  2. About 6 x 10^3 K
  3. About 1.5 x 10^7 K
  4. About 10^5 K
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Correct answer: A. About 3 x 10^9 K

Setting (3/2)kT equal to 400 keV gives a temperature of about 3 x 10^9 K.

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What is the approximate temperature of the sun's interior?

  1. About 3 x 10^9 K
  2. About 10^12 K
  3. About 1.5 x 10^7 K
  4. About 6000 K
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Correct answer: C. About 1.5 x 10^7 K

The solar interior is near 1.5 x 10^7 K, so only unusually energetic protons fuse.

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More Physics topics

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