question 1
(UFPE) In front of a large vertical wall, a boy claps his hands and receives the echo a second later. If the speed of sound in air is 340 m/s, the boy can conclude that the wall is situated at an approximate distance of:
a) 17 m
b) 34 m
c) 68 m
d) 170 m
e) 340 m
question 2
Read the following text:
… The USS Zumwalt is 29 meters larger than another similar warship, the Arleigh Burke (DDG 51). But it is also 50 times harder to detect compared to today's warships thanks to its angular shape, Captain James Downey told the newspaper Portland Press Herald. Downey is the head of the DDG 1000 program for the US Department of Defense.
The purpose of this "hidden" design is for the ship to be able to navigate without being easily detected in shallower waters close to shore...
Source:BBC.com;
access on 8/19/2016
Regarding the text and wave phenomena, mark the correct alternative:
a) The angular shape of the USS Zumwalt favors the absorption of part of the waves sent by radar, thus, the ship is not detected;
b) The angular shape of the USS Zumwalt favors the diffraction of part of the waves sent by radar, thus, the ship is not detected;
c) The angular shape of the USS Zumwalt favors the reflection of part of the waves sent by radar, thus, the ship is not detected;
d) The angular shape of the USS Zumwalt favors the refraction of part of the waves sent by radar, thus, the ship is not detected;
e) The angular shape of the USS Zumwalt favors the phenomenon of wave interference, so the ship is not detected;
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