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Unformatted text preview: 1.(a) Flashlight and mirror are at rest with respect to spaceship so all times,lengths measured are proper times,lengths. so time in secs measured on spaceship = Lp/c = 300/(3.10 8 ) = 10-6 s. (b) similarly this time is 2Lp/c = 2. 10-6 s. (c) and (d) Suppose observer on ground sees the light (traveling at speed c) catch up with the front of the ship (moving at speed v) in time t 1 Then ct 1 = Lp + vt 1 , where Lp =(1/ ) Lp is the length of the spaceship as measured by him. This gives t 1 = (1/ )Lp/(c-v)= L p c 1 v 2 / c 2 / (1 v / c ) ( L p c ) ! v / c 1 v / c Now suppose he sees the reflected light take a time t 2 to reach the back of the ship again which has moved forward a distance vt 2 in that time so it has only to go a distance Lp - vt 2 (at velocity c) so ct 2 = Lp - vt 2 giving t 2 L p / ( c v ) ( L p / c ) 1 v 2 / c 2 / (1 v / c ) ( L p / c ) 1 v / c 1 v / c so time he sees for light to get back to flashlight is...
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