The brightest stars in a young open cluster will be
A) massive blue main-sequence stars.
B) Cepheid variables.
C) yellow main-sequence stars like the Sun.
D) T-Tauri variables.
E) red giants.
A
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An atom that is excited
a. is also ionized. b. is an isotope. c. has had its electron moved to the lowest energy level. d. can emit a photon when the electron moves to a lower energy level. e. can emit a photon when the electron moves to a higher energy level.
If a magnet produces a force on a current-carrying wire, the wire
A) produces a force on the magnet. B) may or may not produce a force on the magnet. C) none of these
A race car travels 40 m/s around a banked (45° with the horizontal) circular (radius = 0.20 km) track. What is the magnitude of the resultant force on the 80-kg driver of this car?
A. 0.68 kN B. 0.64 kN C. 0.72 kN D. 0.76 kN E. 0.52 kN
Angular momentum is calculated as the
A. product of mass times velocity B. product of mass times angular velocity C. product of moment of inertia times D. product of moment of velocity inertia times velocity angular