RCW11%20solutions

RCW11%20solutions - Recitation ClassWork 11 solutions...

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Recitation ClassWork 11 solutions Physics 204, morning summer 2008 Chapter 28 Concepts & Calculations #44,49 Chapter 29 Concepts & Calculations #46,49 Chapter 30 Conceptual Questions #3 Problem #12 44. CONCEPT QUESTIONS a. The Martian measures the proper time interval Δ t 0 , because the Martian measures the beginning and ending events (the times when the trip starts and ends) at the same location relative to a coordinate system fixed to the spaceship. b. The given distance between Mars and Venus is the distance as measured by a person on earth. That person is at rest relative to the two planets and, hence, measures the proper length. The Martian, who is moving relative to the planets, does not measure the proper length, but measures a contracted length. c. According to the Martian, the time of the trip Δ t 0 is equal to the contracted length that he measures divided by the speed v of the spaceship. SOLUTION a. The contracted length L measured by the Martian is related to the proper length L 0 by Equation 28.2 as () 2 2 11 10 0 22 0.80 1 1.20 10 m 1 7.2 10 m c v LL cc =− = × = × b. The time of the trip as measured by the Martian is 11 2 0 8 0.72 10 m 3.0 10 s 0.80 3.00 10 m/s L t v × Δ= = = × × 49. CONCEPT QUESTIONS a. The passengers would measure a length for the spaceships that does not match the constructed length if the two ships have a nonzero relative speed. This would mean that the ships are moving with respect to one another. If so, the phenomenon of length contraction would occur. b. If the passengers in either ship are moving with respect to the other ship, they would measure a contracted length. c. To calculate the contracted length L , the length contraction formula must be used, as given in Equation 28.2: 2 AB 0 2 1 v c (28.2)
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RCW11%20solutions - Recitation ClassWork 11 solutions...

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