system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can a rocket reach escape velocity of Earth (11.2 km/s) if chemical fuels allow exhaust velocity 4.5 km/s at most?

It seems obvious that higher energy density than original energy density of fuel is impossible - but somehow rockets can gain 63 MJ/kg with fuel which offers only 10 MJ/kg. How is it possible?
gpt
Imagine hitting a tennis ball at 4km/Hr straight up. But then just as it starts to slow down you keep hitting it, moving with the ball so it's always travelling at the same speed. Eventually the resistance from the air reduces as you get higher and higher.

Escape velocity is the speed at which you hit a ball once to make it leave earth permanently. Rockets instead just keep hitting the shuttle over and over again with thrust until they reach this velocity.