The figure shows a 2000 kg cable car descending a high hill. A counterweight of mass 1800 kg on the other side of the hill aids the brakes in controlling the cable car's speed. The rolling friction of both the cable car and the counterweight are negligible. How much braking force does the cable car need to descend at constant speed?
A) 3800 N
B) 2900 N
C) 2000 N
D) 980 N
Answer: A
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Discuss the discovery of galaxies, and the scientific debate that led astronomers to identify them as distant clouds of billions of stars
What will be an ideal response?
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a. the signals are so weak in the radio region. b. the wavelength of radio waves is much longer than the wavelengths of visible light. c. radio telescopes are generally much smaller in diameter than optical telescopes. d. it is very difficult to detect radio waves. e. radio telescopes don't use solid mirrors.
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a. Both rules are based on the conservation of charge. b. Both rules are based on the conservation of energy. c. The junction rule is based on the conservation of charge, and the loop rule is based on the conservation of energy. d. The junction rule is based on the conservation of energy, and the loop rule is based on the conservation of charge.
A sound intensity of 70 dB is observed at a distance d from the source of sound. What sound intensity would be observed at a distance 2d from the source?
a. 68 dB c. 64 dB b. 67 dB d. 62 dB