am i right?

Question

an express train is hurtling down the tracks, a teeny tiny fly is heading towards afore mentioned hurtling train that hits teeny fly. as the direction the fly moves changes (from flying toward the train, to moving with the train, stuck to the front). there must be a brief moment when the fly is stationary. therefore the train, being in contact with the fly, must also be stationary.

is this right?

Answer 1

No.

As the direction of the fly changes, the 'brief moment' when the fly is stationary only exists if the acceleration is finite.

Here, you have a collision, which is an infinite acceleration for an infintesimal period of time.

Answer 2

No. It does not stop. Newton's law -- an object in motion will remain in motion.