When a star has stopped contracting and settled down, where is it in the H-R diagram?

A. below the main sequence in the lower left
B. in the upper right as a red giant
C. on the main sequence
D. in the instability strip
E. It is not on the H-R diagram at that time.


Answer: C

Physics & Space Science

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In an adiabatic compression, 200 J of work is done on a gas. What is the change in internal (thermal) energy of the gas during this compression?

A) 0 J B) 100 J C) 200 J D) -200 J

Physics & Space Science

When counting particle-in-a-box quantum states in three dimensions, why do we divide the “volume” of only one eighth of a full spherical shell by the “volume” per quantum state? Why not the full shell’s volume?

A. Molecules in a gas can only have positive momentum components. B. A single quantum energy state embraces both positive and negative values for each momentum component. C. A particle’s momentum magnitude must be positive. D. The factor of 2 in the expression h/2L already counts both possible momentum signs. E. We really do include the full shell: the diagram only shows 1/8 of the shell to make it easier to draw. F. Some other reason (specify).

Physics & Space Science

In modern Miller—Urey experiments it is assumed that carbon and nitrogen in the early atmosphere were present as

A) methane (CH4 ) and ammonia (NH3) B) carbon dioxide (CO2 ) and nitrogen (N2) C) carbonates (CO3-) and nitrates (NO3-) D) carbon and nitrogen atoms

Physics & Space Science

A meteor having a mass of 1000 kg moves through outer space, far from all planets and stars and far from all gravitational influences, at a speed of 20 km/s (20,000 m/s). How much work is done on the meteor during a time interval of one second?

A) 20 × 106 J B) 20 J C) 1000 J D) 20 000 J E) None of the above.

Physics & Space Science