You are watching a movie about a superhero and notice that

thesuperhero hovers in the air and throws a piano at some bad

guyswhile remaining stationary in the air. what's wrong with

thescenario?

The momentum is not conserved.

Explanation:

When the superhero throws the piano, he exerts a force on the piano. Newton's third law says that each action has an opposite and equal reaction. In other words, this means that when the superhero throws the piano, the piano also exerts a force on the superhero, therefore, the superhero should recoil. You can visualize a gun being shot to visualize this phenomenon, when the gun is shot, it will tend to go backwards, trying to conserve momentum.