A block sits on a slight incline, held at rest by the frictional force between the block and the incline. Which of the following statements is true?
A. The work done by the frictional force is negative, since the force of friction opposes the direction that the block is being tugged by gravity
B. The work by the frictional force is equal to the gravitational potential energy of the block
C. The frictional force performs no work, since there is no motion of the block
D. The work done by gravity is entirely converted into heat because of the friction present
E. None of these choices are true
Answer: C
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In their attempt to gauge the true shape of our Galaxy, the Herschels concluded that:
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A double-slit interference experiment is performed in the air. Later, the same apparatus is immersed in benzene (index of refraction, n = 1.50), and the experiment is repeated
When the apparatus is in benzene, you observe the interference fringes to be A) more closely spaced as when the apparatus is in air. B) equally spaced as when the apparatus is in air. C) more widely spaced as when the apparatus is in air. D) Impossible to tell without knowing the wavelength of light in use. E) Impossible to tell without knowing the separation between the slits.