A box is being pulled across a rough floor at a constant speed. What can you say about the work done by friction?
a) friction does no work at all
b) friction does negative work
c) friction does positive work
Answer: b) friction does negative work
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Interstellar gas is composed mainly of
A) some hydrogen, but mainly carbon dioxide. B) 10% hydrogen, 90% helium by numbers of atoms. C) 90% hydrogen, 9% helium by weight. D) ammonia, methane, and water vapor. E) only hydrogen.
A high fountain of water is in the center of a circular pool of water. You walk the circumference of the pool and measure it to be 190 meters. You then stand at the edge of the pool and use a protractor to gauge the angle of elevation of the top of the fountain. It is 55°. How high is the fountain?
a. 25 m b. 53 m c. 86 m d. 43 m e. 48 m
An automobile moving along a straight track changes its velocity from 40 m/s to 80 m/s in a distance of 200 m. What is the (constant) acceleration of the vehicle during this time?
a. 8.0 m/s b. 9.6 m/s c. 12 m/s d. 6.9 m/s e. 0.20 m/s
A loop of gas following the magnetic field lines between sunspots' poles is:
A) a flare. B) a ray. C) a coronal hole. D) a prominence. E) a coronal mass ejection.