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a) An earth observer measures the length of a rod to be one meter with her measu

ID: 1326825 • Letter: A

Question

a) An earth observer measures the length of a rod to be one meter with her measuring stick. What would the earth observer measure for this length if the rod were on a spaceship moving at a constant velocity of 0.5 c relative to the earth? Assumed the rod is aligned along the direction of motion.

b) An earth observer measures a time interval of one hour(=3600s) on her clock. What would be the earth observer measure for this time interval if the clock were on a spaceship moving at a constant velocity of 0.5 c relative to the earth?

Explanation / Answer

(a)

from the lenght contraction

L = L' root (1- (v/c)^2

    = ( 1.0 m) root ( 1- ( 0.5c/c)^2

    =0.866 m

(b)

from the timdilation equation

t = t'/root (1- (v/c)^2

=( 3600 s) /root ( 1- ( 0.5c/c)^2

=4156.92 s