At the center of our galaxy, ____
a. material is available to make stars but the region is too cold to support star formation
b. large stars are formed by the collision of smaller stars
c. stars form at the same rate as they do in the spiral arms
d. there is no star formation since there is no gas present
e. there is evidence of recent, rapid star formation and supernova explosions
e
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Two bodies of equal mass m collide and stick together. The quantities that always have equal magnitude for both masses during the collision are
A. their changes in momentum. B. the force each exerts on the other. C. their changes in kinetic energy. D. all of the above. E. only (a) and (b) above.
A sinusoidal electromagnetic wave in vacuum delivers energy at an average rate of 5.00 µW/m2
What are the amplitudes of the electric and magnetic fields of this wave? (c = 3.0 x 108 m/s, ?0 = 4? × 10-7 T ? m/A, ?0 = 8.85 × 10-12 C2/N ? m2)
In our part of the universe, antimatter is
A) non-existent. B) plentiful. C) short-lived. D) long-lived.
A rocket of total mass M and with burnout mass 0.20M attains a speed of 3 400 m/s after starting from rest in deep space. What is the exhaust velocity of the rocket?
a. 6.8E+2 m/s b. 2.1E+3 m/s c. 1.7E+4 m/s d. 2.2E+3 m/s e. 1.1E+3 m/s