“”When a Prius hits a tractor-trailer truck, does the Prius drag the truck ? The laws of physics would indicate that the much larger ACX Crystal would drag the Fitzgerald.””
A Prius weighs about 3,000 pounds and has about a 200 HP motor. An empty truck trailer weighs about 40,000 pounds and has about a 600 HP motor. So yes, the Prius is not going to do much dragging or pushing on the front end of a mack truck when a mack truck weighs 13 times as much and the mack truck HP is 3 times as much.
Now let us look at the Fitzgerald vs Crystal weight and HP.
Fitzgerald weighs 9,000 tons and has 100,000 HP.
Crystal weighs 30,000 tons (the ship mostly had empty containers) and has 38,000 HP.
So when the Fitzgerald gets hung up on the port bow of the Crystal it drags or pushes the bow of the Crystal starboard. At the same time the Crystal is pushing the Fitzgerald ahead.
I believe all of this pushing and shoving explains how the Crystal executes a 90 degree turn in 3 minutes.
The inertia of the Crystal would drag the Fitzgerald (especially if it was temporarily hung up on the anchor) and the higher horsepower of the Fitzgerald would act like a tug boat pushing the bow of the Crystal in a curved arc toward the right.
This would include the presumption then that the Fitzgerald did not reduce power to the engines.
Also, presuming the Fitzgerald was ‘stuck’ to the Crystal, the Fitzgerald would act like a giant rudder attached to the bow of the Crystal.
You are correct in that the difference in mass between the Prius/Truck is much larger than the difference between the Crystal/Fitzgerald, but the principles are the same.
Anyway, there are still many unanswered questions about this incident, and we will probably have to wait until the investigation is complete before we know what happened, and how.