Suppose we observe a source of x-rays that varies substantially in brightness over a period of a few days. What can we conclude?
A) The x-ray source is no more than a few light-days in diameter.
B) The x-ray source is a quasar.
C) The x-ray source contains a black hole with an accretion disk.
D) The x-ray source must have a strong, rapidly varying magnetic field.
A) The x-ray source is no more than a few light-days in diameter.
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Buoyant force is greater on a submerged 10-newton block of
A) lead. B) aluminum. C) same on each
A high-voltage transmission line carries 1 400 A at 600 000 V. What is the power carried by the line?
a. 840 MW b. 370 MW c. 140 MW d. 84 MW e. 233 MW
In a certain region of space, a uniform electric field is in the x direction. A particle with negative charge is carried from x = 20.0 cm to x = 60.0 cm. The particle moves to a position where the electric potential is:
1.higher than before. 2.unchanged. 3.lower than before. 4.unpredictable.
A runaway railroad car, with mass 30 × 10^4 kg, coasts across a level track at 2.0 m/s when it collides with a spring-loaded bumper at the end of the track. If the spring constant of the bumper is 4.0 × 10^6 N/m, what is the maximum compression of the spring during the collision? (Assume the collision is elastic.)
a. 0.77 m c. 0.34 m b. 0.55 m d. 1.07 m