A spaceship is observed from the Earth to be moving toward a star at a speed of 0.80 c. If the distance from the spaceship to the star is 1.6 ly as measured from earth, how far is the star as measured from the moving space ship?
A. 2.1 ly
B. 1.9 ly
C. 1.6 ly
D. 1.2 ly
E. 0.96 ly
E. 0.96 ly
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A man pushes against a rigid, immovable wall. Which of the following is the most accurate statement concerning this situation?
A) The man can never exert a force on the wall which exceeds his weight. B) If the man pushes on the wall with a force of 200 N, we can be sure that the wall is pushing back with a force of exactly 200 N on him. C) Since the wall cannot move, it cannot exert any force on the man. D) The man cannot be in equilibrium since he is exerting a net force on the wall. E) The friction force on the man's feet is directed to the left.
The redshift due to the Doppler effect is caused by
A) sources of light moving toward the Solar System. B) sources of light moving away from the Solar System. C) sources of light obscured by interstellar dust. D) sources of light moving at right angles to the Solar System. E) an effect not yet believed to be understood.
At 96° F the saturation density of air is 0.04 kg/m3 . If the weather report says the relative humidity is 90 % when the temperature is 96°F, the humidity is
a. 10 % b. 0.9 c. 0.004 kg/m3 d. 0.036 kg/m3 e. 0.04 kg/m3
How many quark colors are there?
a. 1 c. 6 b. 3 d. none of the above