Simple puzzle: bicycle motion

[DaveC426913]

TL;DR

Most "puzzles on SocMed are dumb. This one was a least a tiny bit challenging.

Clarification: Assume the bicycle is supported from falling over, but not prevented from moving forward or backward.

 

[anuttarasammyak]

Forward. I am poor at finding the puzzle here.

 

[renormalize]

TL;DR: Most "puzzles on SocMed are dumb. This one was a least a tiny bit challenging.

SPOILER!
The direction of motion depends on the both the angle of pull and the gear ratio:

 

[DaveC426913]

At first, I thought it was simple, but one commenter pointed out a very non-intuitive effect.

I had to go do the experiment myself with my bike to be sure.

Spoiler

Yes, the bike moves backward.
Its weirder than that though. The bike moving backward engages the gears and chain, causing the pedal to rotate counterclockwise, even as it is moving backward (leftward).

I had to make a little diagram to explain it to commenters:

The pedal moves backward with the bike (blue line and arrow) even as it rotates CCW (red arrows).

Pretty cool.

 

[DaveC426913]

The direction of motion depends on the both the angle of pull

The angle of pull is optimally straight back. That's in the instructions, so not optional.

and the gear ratio:

It worked fine in my experiment at the low gear it was in. I cannot say for certain that there is real-world gear ratio that would change the result, but I am open to the possibility that it exists.