Star A is blue, Star B is yellow, and Star C is red. Which one of these is the hottest star?
A. star A
B. star B
C. star C
D. From color, temperature cannot be predicted.
Answer: A
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At what rate is the gravitational force on a 2.0-kg projectile doing work at an instant when the velocity of the projectile is 4.0 m/s directed 30° above the horizontal?
a. +39 W b. ?78 W c. ?39 W d. +78 W e. +25 W
Where do you have to be on the Earth to view a lunar eclipse?
What will be an ideal response?
A long, straight, horizontal wire carries current toward the east. An electron moves toward the east alongside and just south of the wire. What is the direction of the magnetic force on the electron?
A) toward the north B) toward the south C) upward D) downward E) toward the west.
Two radio antennas are 10 km apart on a north-south axis on high mountain tops at the seacoast. The antennas broadcast identical AM radio signals,
in phase, at a frequency of 4.70 MHz. A steamship, 200 km offshore, travels toward the north at 15 km/h and passes east of the antennas. A radio on board the ship is tuned to the broadcast frequency. The reception of the radio signal on the ship is a maximum at a given instant. How much later until the next occurrence of maximum reception? (c = 3.00 × 108 m/s) A) 5.1 min B) 3.8 min C) 6.4 min D) 7.7 min E) 8.9 min