Which of These Accurately Characterizes an Apparent Dilemma in Understanding

question 168

Multiple Choice

Which of these accurately characterizes an apparent dilemma in understanding the spiral arm structure of a typical spiral galaxy?

• A) The measured speeds of stars in the galaxy are exactly correct for the present spiral structure, having spun the observed tightness of the spiral in the typical lifetime of a galaxy.
• B) If the measured speeds of stars in the galaxy had spun the arms into shape, these arms would be far less tightly wound than the observed arms.
• C) If the measured speeds of stars in the galaxy had spun the arms into shape, these arms would be far more tightly wound than the observed arms.
• D) The measured speeds of material in the spiral arms should not have led to any spiral but should have generated a straight bar rotating like a solid object.

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Definitions:

Motor Units Recruited

The activation of a set of motor neurons and their associated muscle fibers, used to generate an appropriate level of force during muscular contraction.

Multiple Wave Summation

A phenomenon where muscle fiber contractions increase in strength due to rapid, repeated stimulation before full relaxation occurs.

Tetanus

An infection resulting from the Clostridium tetani bacterium, leading to muscle contractions, known as tetanus.

Stimuli Frequency

The rate at which stimuli are presented over time, affecting the response of sensory systems.