Cracking a whip faster than the speed of sound is theoretically possible, but the sound of the crack would not be heard if the whip is cracked while moving faster than sound. The perception of the sound depends on the direction of the movement relative to the whip's crack. Inside a plane, one could crack the whip and hear it, while outside, cracking it forward would not allow for hearing the sound. However, cracking it backward might still produce audible results. The discussion highlights the relationship between speed, sound, and the direction of movement.