The phrase "jerks down" is often used to describe sudden and forceful movements. However, there are several synonyms available that can express the same idea in different ways. For example, you can use the term "plummets" to indicate a swift and uncontrollable descent. Alternatively, the phrase "drops abruptly" can be used to convey a sudden and unexpected drop. Similarly, the term "yanks" can be used to suggest a sharp and forceful pull, while "snaps down" can convey a sudden and jarring movement. Ultimately, the choice of synonym will depend on the context of the sentence and the tone you want to convey.