Eli5 why do falcon heavy boosters gain altitude after disconnecting

Question

I was watching a falcon heavy launch on YouTube. In the corner of the screen it shows speed and altitude of the rocket, I noticed that once the boosters disconnected they continued to gain altitude before finally coming back down to earth. Iscit the momentum that carries them further?

In: 1

Answer 1

Eli5: throw a baseball upwards. After it leaves your hand, it’s no longer receiving power. But it will sure fly a way up won’t it?