system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are bullet trains shaped like a rounded bullet? Shouldn’t a sharp tip like a spearhead make it more streamlined?
gpt
Aerodynamics can get quite odd at high speeds. A needle-sharp point isn't always the most efficient shape. There are also important concerns other than top speed and efficiency, like noise and overall length. Bullet trains need to be quiet, because they pass through a lot of populated areas. Sharp points and steep angles can increase wind noise. Trains also have a maximum non-articulated length that dictates how long any single car can be and still be able to make the turns in the track. The pointier the nose is the less internal volume is left over for all the stuff that needs too be in a locomotive.