Final answer:
If an opponent's free hand touches the playing surface during a rally in sports like table tennis, it is considered a fault and the opponent is awarded a point. This rule is in place to prevent unfair advantage and interference with play.
Step-by-step explanation:
The question 'What happens if your opponent's free hand touches the playing service?' seems to pertain to a rule in a sport such as table tennis or tennis. Typically, in sports like table tennis, if a player's free hand touches the playing surface during a rally, it is considered a fault and the opponent is awarded a point. This is because touching the playing surface with a free hand can provide an unfair support or can interfere with the play. Touching the playing surface during a rally is explicitly prohibited by official rules.
In the scenarios described involving a tennis racquet and baseball bat, the question of hand contact with the playing surface does not directly apply. However, these examples illustrate the importance of how contact points affect the force exerted on the player and potential vibrations. Similarly, in sports like table tennis, technique and proper contact with the ball are key to preventing unintended movements, such as a free hand touching the table.