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In the last fight scene of "Star Trek: Nemesis", Picard rammed the Enterprise into Shinzon's Warbird. The trick worked to damage the warbird to some extent, but the Enterprise attached itself to the Warbird with its grips.

After the collision Shinzon said, "Divert whole power to engines. Full Reverse!!!" and the Warbird started to reverse. By doing so the Warbird detaches itself from the Enterprise. How is it possible?

This doesn't make sense from a physics standpoint, since the Enterprise should move with Warship as there was no external resistance to the force applied by the Warship against the Enterprise and the Enterprise was attached to it (forming system of Warship + Enterprise)!

Do you have an explanation of why it happened this way?

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Imagine tying a thin piece of string to a box and pulling on it. Normally, you'll just pull the box along with you, but if you pull with enough force, the string breaks instead. The amount of force you have to apply to the string to break it is called its failure point. Every object has one.

In particular, the same goes for the grips holding the Enterprise and the warbird together; they have a failure point, and if they are subjected to a force stronger than that failure point, they will break. Evidently the warbird's engines were able to supply enough force that the failure point of the grips was exceeded.

Inertia does play a role in determining how much force is exerted on the grips, but I would say it's only indirectly involved.

All this assumes that the two ships are subject to known Newtonian physics, of course.

This question inspired me to make a blog post which explains the answer.

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  • Thanks.. your answer looks less polished, but its the real answer!!! – 11.01.11 Dec 30 '11 at 5:35
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    You've downplayed the role of inertia too much. It is directly involved, because without two opposing forces acting on an object it will never reach its failure point. – gnovice Dec 30 '11 at 6:17
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    @gnovice: we could quibble over the meaning of "direct" or "indirect," that's why I said "I would say it's only indirectly involved." We agree that inertia is involved in producing the tensile force on the grips, and on every other part of the ships. However, once the existence of that tension is established, you can take a local view of the grips in which inertia isn't relevant, and it's the failure point that really determines that the grips break (and e.g. that the warbird's engine mounts don't). – David Z Dec 30 '11 at 7:23
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    @DaveMG: that's fair, some of this stuff is counterintuitive (even to those who study it). I do think what you're confused about could make a good physics question, if you would like to ask it. Or I'd be happy to explain this in more detail in a chat room, but unfortunately I don't have time to do so tonight. – David Z Dec 30 '11 at 7:34
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    @Celeritas in the context of this answer, the "grips" are whatever holds the two starships together. They could be broken pieces of metal, for example. – David Z Aug 12 '14 at 20:52
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The Enterprise didn't move along with the warship because of inertia (i.e. "a body at rest tends to stay at rest"). When the warship reversed thrusters and pulled away, the inertia of the massive Enterprise acted as the opposing force, and the difference between these forces overcame the friction from the twisted, entangling wreckage and allowed the ships to separate.

Ships do have inertial dampers, but these force fields act primarily on objects within the ship (notably, the crew) to keep them from experiencing the effects of extreme accelerations. Inertial dampening fields, as I understand it, don't actually reduce the inertia of the ship itself. Instead, structural integrity fields are used to increase the effective strength of the materials in the hull so they can resist the effects of extreme stresses. Therefore, the full 3.25 million metric tons of Enterprise-E made for a rather significant inertial force resisting the pull of the reversing warbird.

EDIT : To explain with a simpler example, you can consider this example of inertia, in which a heavy object is supported by string A and has another string B hanging below it. If you pull slowly on string B, string A will snap first because the weight of the object combined with the pulling force stress string A more. However, if you pull hard on string B, the inertia of the heavy object resists the sudden movement and causes higher stresses on string B, snapping it first.

The full-power reverse of the warship thrusters is equivalent to a sharp tug on string B, string B is equivalent to the wreckage holding the ships together, and the heavy mass is the Enterprise.

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    That of course is not to say that the Enterprise-E wasn't moved by the warbird pulling away. It was just moved less, thus allowing the warbird to detach itself from the collision. – Xantec Dec 29 '11 at 18:30
  • Your explanation looks OK to everyone, but you are saying: A warp-capable engine (which was able to move warbird from rest to warp-factor speed) can't accelerate mass of warbird & Enterprise combined to much smaller speed. Mind it, Enterprise was attached with warbird... – 11.01.11 Dec 30 '11 at 5:27
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    @Sachin: First, the warship was reversing using sub-light thrusters, not the warp engines. Second, the "attachment" between the ships was relatively weak. It was a bunch of wreckage holding the ships together. The internal skeletal structures of the ships were not bonded to one another, either physically or through structural integrity fields, so there's no reason to believe the collided ships will simply behave as one larger ship would. – gnovice Dec 30 '11 at 5:52
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    As another answer says, inertia is indirectly involved.. Think about it: The mass of warbird had inertia too, but still its engines were able to move it because of high failure point of its structural bonding. Warbird's own part could be detached if it fails to maintain its failure point. This is how a system works in physics.. – 11.01.11 Dec 30 '11 at 6:19
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    @SachinShekhar You seem to be making big assumptions about how much friction was holding the two ships together. – Brian Ortiz Dec 31 '11 at 6:21

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