What happens if B2 swings and misses for strike three while R1 is sliding into second base and the bat strikes the catcher?

In this scenario, the fundamental rule at play involves the concept of interference in baseball, particularly regarding the batter's actions affecting the play on the field. Since B2 swung and missed for strike three, he is already out. However, his bat striking the catcher while R1 is sliding into second base constitutes interference.

In this situation, the action of B2 using the bat in a manner that results in the catcher being struck is viewed as an obstruction of the catcher’s ability to make a play on R1. The fact that the batter did not intend for this to happen does not negate the call. Interference is called because the bat’s contact with the catcher impedes the catcher's ability to defend against the sliding baserunner.

Consequently, since B2 is guilty of interference due to the swing of the bat affecting the play at second base, both B2 and R1 are declared out. The out on R1 is a result of the interference directly caused by B2's actions, leading to the enforcement of this rule regarding the batter's interference impacting the play.