Why do rockets need multiple stages?

Answer: Shed empty weight during ascent

Backup systems in case of failure — Wrong. Stages aren't backups—each stage fires sequentially. Staging allows the rocket to shed heavy, empty components to maintain acceleration.

Spread payload across sections — Wrong. Payload stays in the final stage. Earlier stages are dropped after their fuel is spent to reduce the mass that must be accelerated.

Shed empty weight during ascent ✓ — Correct! Rockets shed (drop) empty fuel tanks and engines as stages complete, reducing mass. Carrying empty tanks wastes energy. Each stage fires, empties, then separates. This improves efficiency—less mass means less fuel needed to accelerate the remaining rocket.