Which of these is a reason for using mirrors rather than lenses in telescopes?
A. Lenses can only be supported by their edges, making them sag in the middle (mirrors can be supported from behind).
B. Most transparent materials focus light of different colors to different spots.
C. Lenses are more expensive to make than mirrors.
D. All of these choices are correct.
Answer: D
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A car is moving with a constant acceleration. At t = 5.0 s its velocity is 8.0 m/s and at t = 8.0 s its velocity is 12.0 m/s. What is the distance traveled in that interval of time?
A) 10 m B) 20 m C) 30 m D) 40 m E) 50 m
In the figure, a T-bar ski tow pulls a skier up a hill inclined at 10° above horizontal. The skier starts from rest and is pulled by a cable that exerts a tension T at an angle of 30° above the surface of the hill
The mass of the skier is 60 kg and the effective coefficient of kinetic friction between the skis and the snow is 0.100. What is the maximum tension in the cable if the starting acceleration is not to exceed 0.400 g? A) 246 N B) 366 N C) 431 N D) 187 N E) 535 N
The Ptolemaic model of the universe:
A) explained and predicted the motions of the planets with deferents and epicycles. B) is the basis of our modern cosmology. C) could not account for the stellar parallax observed by Hipparchus. D) describes the orbits of the planets as being ellipses, not circles. E) always kept Mars and Mercury between the Earth and Sun.
According to Faraday’s Law of Electromagnetic Induction, the induced voltage is equal to
A. the rate of change of the magnetic flux B. the rate of change of the magnetic field strength C. the rate of change of the magnetic force D. the rate of change of the loop area