Using 1000 J of work, a toy elevator is raised from the ground floor to the second floor in 20 s. How much power does the elevator use?
A) 20 W
B) 50 W
C) 100 W
D) 1000 W
E) 20,000 W
Answer: B
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Dark matter is ___
a. a cloud of black holes and brown dwarfs in the galactic halo b. extremely cold, supermassive molecular clouds in the disk c. an unknown type of mass that does not emit or absorb photons d. the substance of which black holes are made e. a theory to explain galactic formation that has been proven wrong
You lift a book with your hand in such a way that it moves up at constant speed. While it is moving, what is the total work done on the book?
a) mg × ?r b) FHAND × ?r c) (FHAND + mg) × ?r d) zero e) none of the above
Emission nebulae are blue
Indicate whether the statement is true or false
The distance between successive nodes for a standing wave pattern is ________ the wavelength (give multiple or fraction).
Fill in the blank(s) with the appropriate word(s).