A Carnot heat engine operates between 400 K and 500 K. Its efficiency is:

A. 20%
B. 25%
C. 44%
D. 79%
E. 100%


Answer: A. 20%

Physics & Space Science

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: Compare the relative reflected intensity in air from the surface of sodalime silica glass with an index of refraction of 1.51 and dense optical flint glass with and index of refraction of 1.65.

What will be an ideal response?

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A 250 g block is dropped onto a relaxed vertical spring that has a spring constant of k = 2.5 N/cm (Fig. 7-30 ). The block becomes attached to the spring and compresses the spring 12 cm before momentarily stopping. While the spring is being compressed, what work is done on the block by

(a) the gravitational force on it and
(b) the spring force?
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(d) If the speed at impact is doubled, what is the maximum compression of the spring?
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Physics & Space Science

An exoergic reaction

a. absorbs energy. b. requires a high temperature. c. releases energy. d. occurs only in stars.

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A single slit of width a is illuminated by light of wavelength l. If a = 4.3l, the maximum number of dark fringes on a semi-circular screen surrounding the slit is

a. 2. b. 4. c. 6. d. 8. e. 9.

Physics & Space Science