Which is more common: a star blows up as a supernova, or a star ejects a planetary nebula?
A) Planetary nebulas are more common.
B) Supernovae are more common.
C) They both occur in about equal numbers.
D) It is impossible to say.
A) Planetary nebulas are more common.
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When total internal reflection happens at a plastic-air interface
A. half the light is refracted. B. half the light is reflected. C. light hits the interface from the air side. D. light hits the interface from the plastic side. E. the law of reflection ceases to hold.
When you remove electrons from a metal cup, the cup becomes
A) negatively charged. B) positively charged. C) ionized.
A 10,000-kg rocket blasts off from earth with a uniform upward acceleration of 2.00 m/s2 and feels no air resistance. The upward thrust force its engines must provide during this acceleration is closest to
A) 20,000 N. B) 980,000 N. C) 118,000 N. D) 78,000 N.
A river has a steady speed of 0.30 m/s. A student swims downstream a distance of 1.2 km and returns to the starting point. If the student swims with respect to the water at a constant speed and the downstream portion of the swim requires 20 minutes, how much time is required for the entire swim?
a. 50 minutes b. 80 minutes c. 90 minutes d. 70 minutes e. 60 minutes