When they were first discovered, quasars appeared to be____
a. small, star-like objects associated with radio emission
b. pairs of radio sources
c. elliptical galaxies with an X-ray emitting halo
d. clouds of gas glowing with green emission lines
e. linear jets of matter
a
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Which statement is NOT true about open clusters?
A. After a molecular cloud has collapsed and formed many stars, the cloud dissipates and the stars spread out into an open cluster. B. Open clusters are gravitationally bound and therefore have a spherical shape. C. Open clusters typically contain dozens to hundreds of stars. D. Open clusters usually contain many blue stars.
A fusion reaction releases energy because the binding energy of the resulting nucleus
A) is less than the binding energy of the original nuclei. B) is absorbed in the process. C) is equal to the binding energy of the original nuclei. D) is greater than the binding energy of the original nuclei. E) is released in the process.
The position of a particle moving along the y axis has a position given by
?
?
Is there any time interval during which the particle is not moving?
A. Yes, from 0.60 s to 1.00 s. B. Yes, from 0.795 s to 0.805 s. C. Yes, at the time t = 0.80 s. D. No, the velocity is never zero. E. No, an instant is not the same as a time interval.
Kieran takes off from rest down a 50 m high, 10° slope on his jet-powered skis. The skis have a thrust of 280 N parallel to the surface of the slope. The combined mass of skis and Kieran is 50 kg (the fuel mass is negligible)
Kieran's speed at the bottom is 40 m/s. What is the coefficient of kinetic friction of his skis on snow? A) 0.23 B) 0.47 C) 0.58 D) 0.29