Special relativity barn pole thought experiment

[lei123]

Homework Statement

cookie dough lies on a conveyor belt which moves at speed v. A circular stamp stamps out cookies as the dough rushes by beneath it. When you buy these cookies in a store, what shape are they? That is, re they squashed in the direction of the belt, stretched in that direction, or circular? You don't have to be quantitative, but you must explain your (qualitative) reasoning in both the lab frame and the conveyor belt frame.

Homework Equations

n/A

The Attempt at a Solution

in the lab frame, the cookies will come out circular because the motion of the cookies are analogous to the motion of the conveyor belt and from that perspective the stamp is very much a circle.
in the conveyor belt frame, I'm much more lost. What's the difference between being squashed and being stretched in the direction of the conveyor belt?

 

[Filip Larsen]

It sounds to me that this thought experiment is very similar to the barn pole thought experiment, although it seems a bit harder to picture relativistic cookies than relativistic poles :).