Physics relativty, defraction, refraction problems?

Posted on 2017-03-20 18:51:00 in Physics by JOHNNY

1. As you stand in your backyard on a clear night, an alien spacecraft flies overhead with a speed of 0.80c from a great distance. The alien pilot on the spacecraft turns on his searchlights for 4.00ms as measured by him. (a) How long was the searchlight of the spacecraft on as measured by you? (b) In the time that the searchlight was on, how far did the spacecraft travel as measured by you? 

2. a spaceship flies past mas with a speed of 0.978c relative to the surface of the planet. when the spaceship is directly overhead the planet mars parallel to the ground, the pilot saw a very bright signal light on the martian surface blinking on and off. the pilot also a billboard sign appearing to be a square with 4.00m on the side. the pilot observed that the signal was on for 82.4us. (a) what is the duration of the light pulse as measured by an observer on mars and (b) what are the new dimensions of the billboard according the the mars observer. 

3. two speakers A, and B are 5.50 m apart and are emiting identical in phase sound waves. the speed of sound in air is 344m/s. consider a line which is the perpendicular bisector of the line connecting the two speaker. the first interference maximum occurs at +- 28.2 deg from this line. (a) what is the frequency of the sound emitted. (b) find the rest of angle where constructive and destructive interferance occur.

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