As you are standing on the lakeshore on a calm day, a friend in a boat 300 m offshore calls out to you. Simultaneously, a friend who is 300 m inland yells to get your attention. Which one will you hear first?
A. the friend offshore
B. the friend inland
C. you will hear both at the same time
D. sound can't carry that far
B. the friend inland (assuming the air is warmer over the land than the water)
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A 1-kg mass at the Earth's surface weighs
A) 1 N. B) 5 N. C) 10 N. D) 12 N. E) none of the above
If the wavelength of a photon is the same as the de Broglie wavelength of an electron, which one has the greater momentum?
A) The electron because it has more mass. B) The photon because it is traveling faster. C) They both have the same momentum.
A ceiling fan is turned on and reaches an angular speed of 60 rev/min in 20 s. It is then turned off and coasts to a stop in 40 s. In the one minute of rotation, through how many revolutions did the fan turn?
a. 30 c. 0 b. 60 d. 600
Some stars vary in brightness. What observing technique is best for observing the details of the changes in brightness?
A) Time-monitoring because we want to track how the brightness changes with time. B) Imaging because an image will show the star getting brighter and dimmer. C) Spectroscopy because changing brightness means changing temperature. D) All of the above are equally useful in detecting variation in brightness.