When a propeller airplane takes off, how is momentum conserved?
a. Momentum is not conserved, because the airplane goes from being still to moving.
b. Momentum is conserved only because the earth moves as the airplane takes off.
c. Momentum is conserved because molecules in the air move as the propeller pushes them.
d. Momentum is conserved because molecules in the air move on average in all directions.
e. Momentum is conserved because another airplane has to take off from the other side of the earth at the same time.
c
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If a galaxy is found receding from us at 894 km/sec and it is located at a distance of 12 Mpc, what is the age of the universe if the universe is flat?
a. about 20 billion years b. about 1.3 billion years c. about 13 billion years d. about 9 billion years e. about 90 billion years
In a hydrogen atom, a transition from the third to the second energy level will produce:
A) a red emission line. B) a blue green absorption line. C) a violet emission line. D) an infrared emission line. E) an ultraviolet absorption line.
A 1.33 kg dense mass is on the end of a 4.50 m "string"
(a) What would be the period of the pendulum on Earth? (b) If the mass were doubled, what would be the frequency of oscillation? (c) What would be the period on the planet Mars where gravity is 38.% that of the Earth?
A circuit contains two inductors of 6.0-mH inductance in parallel placed in series with an inductor of 8.0-mH inductance. After one of the 6.0-mH inductors burns out, the repairman wants to replace all three inductors with one inductor of equivalent inductance. Assuming inductors combine in series and parallel the same way resistors do, what inductance should he use?
a. 3.0 mH b. 3.4 mH c. 4.8 mH d. 11 mH e. 20 mH