Turtle crawling on elastic cable

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SUMMARY

The discussion centers on a mathematical problem involving a turtle crawling on a super elastic cable that stretches infinitely. The turtle moves at a constant speed of 1mm per second, while the cable stretches at a rate of 1km per second. The initial calculations suggested that the turtle would reach the end of the cable in 1000 seconds, but this conclusion is incorrect due to the turtle's position being influenced only by the segment of the cable behind it, not the entire length. The correct understanding reveals that the turtle never reaches the end of the cable despite the calculations indicating otherwise.

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Homework Statement


A turtle is crawling along a cable made of super elastic material. The turtle speed is constant at 1mm per second. The cable's length is 1km and at the same time it is being stretched at a constant speed of 1km per second. Suppose the turtle is immortal and the cable can be stretched infinitely long, will the turtle reach the other end of the cable? If so, how long will it take?
The stretching of the cable also causes the turtle to move together with the point it's at.

Homework Equations



The Attempt at a Solution


Cable length over time l(t) = Initial length + cable length growth = 1 + 1t

Turtle position over time x(t) = Initial speed over time + cable length growth = 0.001t + 1t = 1.001t

For turtle to reach the end:
x(t) > l(t)
1.001t > 1 + t
t > 1000s
Hence turtle will reach end of cable in 1000s.

So what I did is actually wrong. Can somebody explain why?

At 10s, cable length is 11km while turtle position is at 10.01km
At 100s, cable length is 101km while turtle position is at 100.1km
At 1000s, cable length is 1001km while turtle position is also at 1001km
Why is this wrong? Did I misunderstood how the turtle's position will change with the stretching of the cable?
 
Physics news on Phys.org
Turtle doesn't advance with the cable length increase of the whole cable. Only with the increase of the piece behind him/her (how do you distinguish a female turtle from a male one ?)
 

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