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Basic Astrophysics

1) The energy source of stars is primarily associated with :

a) the reactions of atoms in the core
b) the reactions of nuclei in the core
c) the reactions of atoms in the outer regions
d) burning of elements until they become radioactive
e) burning of elements heavier than lead.

2) Which of the following affect the life of a star?

a) Gravitational force
b) pressure
c) temperature
d) fusion
e) all of the above.

3) Differences in how a star appears in the sky are a function of:
a) the size of the star
b) how far away the star is from Earth
c) the total energy emitted by the star
d) the star's apparent magnitude
e) all of above.

4) One difference between the motion of electrons in an atom and the motion of planets in the solar system is that:

a) gravity holds the planets in orbit while centripetal force holds the electrons.
b) electron orbits are uniform,planetary orbits are not.
c) brownian motion applies to planets but not electrons
d) the orbit planet is constantly being accelerated
e) all of the above appply to both planets and electrons.

5) What is an atom's spectrum?
a) the total collection of photons an atom can reflect
b) sum of photons an atom will emit
c) the atomic mass of the atom
d) the atom's place in the periodic table
e) the allowed orbit closest to the nucleus.

6) In the quantum world uncertainties exist in our knowledge of:
a) the positions and velocities of objects when we first start observing them.
b) the velocities and positions of objects after they have undergone a change.
c) the differences between the electrons and photons.
d) a&b
e) a, b, c

7) Newtonian mechanics works for objects with large masses because :
a) we have no method of measuring velecoties to the accuracy required in quantum mechanics.
b) planck's constant masks the uncertainties.
c) the uncertainty of the measurements is indistinguishable from zero.
d) a&c
e) a,b, c

Solution Preview

Hello and thank you for posting your question to Brainmass.

Here are my answers:

1) The energy source of stars is primarily associated with :

a) the reactions of atoms in the core
b) the reactions of nuclei in the core
c) the reactions of atoms in the outer regions
d) burning of elements until they become radioactive
e) burning of elements heavier than lead.

The answer is (b). The fusion reaction occurs in the core when light nuclei combine to create heavier nucleii. Due the temperature the gas is completely ionized (no electrons orbiting the nucleus).

2) Which of the following affect the life of a star?

a) Gravitational force
b) pressure
c) temperature
d) fusion
e) all of the above.

The pure answer is (a), due to gravity the gas in the star collapses on itself, heating up, starting a fusion process that creates a hydrodynamic pressure in the gas that prevents the collapse of the star until all nuclear reaction stop. Then gravity will pull the star further in on itself. The life cycle of the star completely depends on its mass (hence gravity).

3) Differences in how a star appears in the sky are a function of:
a) the ...

Solution Summary

The solution explains in detail why the chosen answer is the correct one.

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