A 3 solar mass main sequence star is at a larger distance than a 0.4 solar mass main sequence star. Which star appears brighter?
A. The 3 solar mass main sequence star.
B. We cannot tell with the information given.
C. The 0.4 solar mass main sequence star.
D. The stars are approximately the same brightness.
E. It depends on the phase of the Moon.
Ans: B. We cannot tell with the information given.
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The lowest energy level in an atom is
a. the absolute zero temperature. b. the ground state. c. the ionization level. d. responsible for Doppler shifts. e. the energy level from which the Paschen series of hydrogen originates.
Which of the following is a contribution that Galileo made to astronomy?
A. He discovered four moons (or satellites) of Jupiter. B. He discovered epicycles. C. He determined the size of Earth. D. He developed the first successful heliocentric theory.
A 1200-kg car is being raised with a constant acceleration of 2.53 m/s2 by a crane, using a 20-m long steel cable, 1.5 cm in diameter. Young's modulus for steel is 20 × 1010 N/m2. What is the change in length of the cable?
A) 8.4 mm B) 8.4 cm C) 4.9 mm D) 4.9 cm E) 4.9 m
An electron has the same de Broglie wavelength as a 390 nm photon. The speed of the electron is closest to:
A) 1,900 m/s B) 2,100 m/s C) 1,700m/s D) 1,500 m/s E) 540 m/s