Whip has a few different meanings such as to beat (a person or animal) with a whip or similar instrument, especially as a punishment or to urge them on and an official of a political party appointed to maintain discipline among its members in Congress or Parliament, especially so as to ensure attendance and voting in debates.
Another meaning of whip is a strip of leather or length of cord fastened to a handle, used for flogging or beating a person or for urging on an animal.
Cracking the Whip means to make someone else behave better or work harder.
When you crack the whip you use your authority to make someone else behave better or work harder.
An example of how to use cracking the whip or crack the whip in a sentence would be.
The construction crew was two months behind schedule, so the boss decided it was time to crack the whip and get the job done.
Another meaning of cracking the whip is to push or urge someone (usually one's subordinate) to work harder, likened to literally cracking a whip to control or urge on an animal.
When you crack the whip it makes an animal such as a horse or donkey etc to work harder or at least begin to work.
The cracking the whip expression was first recorded and originated in the year of 1647 and it alludes to drivers of horse-drawn wagons who snapped their whips hard, producing a loud cracking noise.
When they did that cracking the whip the horses would start walking to get the horse drawn wagons moving.