Bombs like the GBU12 will accelerate forever in freefall, this is getting very obvious when dropping them from higher altitudes.
When spawning a GBU12 at 55km altitude and using setVectorDirAndUp to aim it straight to the ground the GBU12 will reach around 3700km/h upon impact on ground, roughly 108seconds after spawning it.

Edit:
Can a mod please delete the png images, did upload the wrong files, jpgs are the correct ones. {F23606} {F23607}