Relativity - Length Contraction Problem

AI Thread Summary
The discussion centers on a homework problem involving length contraction in relativity, where two spaceships travel the same distance at different speeds. The first ship takes 26.8 minutes and the second 28.2 minutes to cover 14 light-minutes, leading to a calculated ratio of their lengths at rest. The initial calculation suggests a ratio of 1.01918, indicating the first ship is longer, while the teacher asserts the correct ratio is 0.9823, implying the opposite. This discrepancy raises conceptual questions about length contraction, as the faster ship is expected to be more contracted and thus shorter. The discussion highlights confusion regarding the relationship between speed, time taken, and perceived lengths of the ships.
Jacob Ward
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Homework Statement


You are watching a race between two space ships who pass you moving at different constant speeds. In your reference frame, both ships are the same length while moving. It takes the first ship 26.8 minutes to get to the finish line a distance 14 light-minutes away. It takes the second ship 28.2 minutes to travel the same distance. What is the ratio of the length of the first ship to that of the second ship when they are both at rest?

Homework Equations


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

The Attempt at a Solution


TimeShip1 = 26.8 (*in minutes*);
TimeShip2 = 28.3 (*in minutes*);
DistanceOfRace = 14 (*in light-minutes*);
VelocityShip1 = DistanceOfRace/TimeShip1;
VelocityShip2 = DistanceOfRace/TimeShip2;
LengthShip1 = ?
LengthShip2 = ?

L'=LengthShip1*Sqrt[1 - (DistanceOfRace/TimeShip1)^2] =
LengthShip2*Sqrt[1 - (DistanceOfRace/TimeShip2)^2]

LengthShip1/LengthShip2 = (1/Sqrt[1 - (DistanceOfRace/TimeShip1)^2])/(1/
Sqrt[1 - (DistanceOfRace/TimeShip2)^2]);

I get an answer of 1.01918 but my teacher says the answer is 0.9823 which is exactly the inverse.
This doesn't make sense to me conceptually because if the first ship is going faster (less time to complete the race) it's length should be contracted more which means it is naturally longer than ship 2 and therefore the ratio of ship 1 to ship 2 should be greater than 1 right? which would support my answer.
 
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I agree that the ratio should be greater than 1 and I agree with your reasoning. (I haven't check the numerical answer.)
 
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