Steve:
The whip’s pop is a result of the tip of the whip (the “popper”) moving beyond the speed of sound and creating a vacuum in space. The air rushing back into the vacuum makes the pop sound. A whip generates its speed through the “conservation of energy”. The body of the whip is built to be a continually shrinking diameter from the thick handle down to the tip of the popper which is only a few strands of fiber. A little energy imparted at the handle accelerates along the diminishing diameter until the popper is moving over 700 miles/hour. You scientists can post the exact speed of sound (someone’s .sig says that “the speed of time is one second per second” 
The speed of sound is 343 Meters per second or about 154 miles per hour in air, sound in other mediums has a different rate of travel. Air temperature and air density (mostly from humidity) effect this speed but it is good enough for general discussion purposes