Planetary density will decrease. Planetary years will become longer. Planetary days will become shorter. Planetary gravity will become stronger.
I gave my students this multiple choice question: An astronomer observes that a planet rotates faster after a meteorite impact. Which is the most likely effect of this increase in rotation?

Only one answer is correct among these 4 choices:
- Planetary density will decrease.
- Planetary years will become longer.
- Planetary days will become shorter.
- Planetary gravity will become stronger.

Could you tell me which one is correct?

Planetary days will become shorter.