How many molecules are in:
(a) 1.0 cm3 of AIR at STP?
(b) 1.0 cm3 of HELIUM at STP?
2.7 × 1019 molecules/cm3 for both
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Answer the following statement(s) true (T) or false (F)
1. An inertial clock present at two events always measures a shorter time than a pair of synchronized clocks in any inertial reference frame would register between the same two events (as long as the events don’t occur at the same place in that frame). 2. Consider a train moving at a speed of 0.5 relative to the ground. A light in one of its windows blinks repeatedly. An observer on the ground will necessarily see (not observe) those blinks to be separated by a larger time interval than a person on the train would.
A string is stretched and fixed at both ends, 200 cm apart. If the density of the string is 0.015 g/cm, and its tension is 600 N, what is the fundamental frequency?
a. 316 Hz b. 632 Hz c. 158 Hz d. 215 Hz e. 79 Hz
Intensity of Sound: The sound intensity level 5.0 m from a point source is 95 dB. At what distance will it be 75 dB?
A. 25 m B. 50 m C. 75 m D. 225 m
Uranus and Neptune appear blue or blue-green because
a. their atmospheres absorb blue light very efficiently. b. their solid air-less surfaces are this color c. their surfaces are covered with liquid water with no atmosphere d. traces of methane in their atmospheres absorb red light very efficiently.