A 20.0-kg traffic light hangs midway on a cable between two poles 30.0 meters apart. If the sag in the cable is 0.40 meters, what is the tension in each side of the cable?
a. 9.8E+1 N
b. 9.8E+3 N
c. 3.7E+3 N
d. 3.8E+2 N
e. 2.0E+4 N
c
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Potential: A proton that is initially at rest is accelerated through an electric potential difference of magnitude 500 V. How much kinetic energy does it gain? (e = 1.60 × 10-19 C)
A. 500 J B. 8.0 × 10-17 J C. 1.6 × 10-19 J D. 800 J
Two hypothetical discoveries in Part A deal with moons that, like Earth's moon, are relatively large compared to their planets. Which of the following best explains why finding 1 planet with such a moon is consistent with the nebular theory, while finding 6 planets with such moons is not consistent?
a. Unusually large moons form in giant impacts, which are relatively rare events. b. The nebular theory says that only planets at least as large as Earth can have large Moons, and 6 Earth-size planets would not be likely to form in one solar system. c. The nebular theory holds that moons of any size should be rare, so finding 1 is not too surprising but finding 6 would be very surprising.
A pulsar (a rotating neutron star) emits pulses at a frequency of 0.40 kHz. The period of its rotation is
A) 2.5 ms. B) 2.5 s. C) 0.025 s. D) 0.25 s. E) 25 ms.
Spectra for the Cygnus loop and the Orion nebula are shown above. Which of these is seen in the Orion nebula, but is not clearly visible in the Cygnus loop spectrum?
A) ionized sulfur B) atomic helium C) atomic hydrogen D) ionized oxygen