I loved the Indiana Jones and the Kingdom of the Crystal Skull. Sure the plot was ridiculous and there were a lot of “Lucas moments”, but it was a legitimately fun film. The nuke scene alone is worth the price of admission. I’m sure the fine folks at Insultingly Stupid Movie Physics will have a field day with it, but come on: it’s an Indiana Jones movie.
But there are a few teachable moments regarding physics in the film. Here’s one, Newton’s First Law. As everyone knows, when you drive in your car and turn or break, your body naturally continues in the same direction and it takes force from the seat or seatbelt to change your momentum. This is especially notable when standing, as in an accelerating subway train - you feel as though a force is pushing you backward (of course it’s really the floor accelerating you forward).
So if you’re in a swordfight(!) on the back of a fast moving jeep, you’ll not be able to stay standing very long if there’s any turning or changing speed. I hesitate to guess the weight of the lovely Cate Blanchett, but if she weighs 135 pounds and the jeep slows by 5 miles per hour in 2 seconds, that’s equivalent to to some 15 pounds of force pushing her off balance. By the way, the equation for the force (make sure to use consistent units!) is
Swordfighting with Shia LeBouf would be difficult under these circumstances - not that he’d be doing any better. He weighs more, so there would be correspondingly more force pushing him off.
But in a movie with alien skulls in Area 51, I can forgive a little looseness with momentum. Go see the film if you haven’t already!
UPDATE: An insightful commenter remembers a much more egregious lack of momentum in the film, which I completely forgot. You should check it out below!
3 responses so far ↓
1 Evan Berkowitz // May 25, 2008 at 9:30 am
… of course, Shia LeBouf has inertia exactly proportional to his mass, so the accelerations that his and Cate’s bodies would undergo are… identical.
2 CCPhysicist // May 26, 2008 at 6:57 pm
Having the benefit of reading this blog just before going to see the movie, I was watching that scene and didn’t find it to be all that bad. They get knocked around when the vehicles change direction.
The biggest bit of nonsense involved the jet powered sled. The real one used a rocket, not a jet engine, and the deceleration when it hit the water was close to 50 G’s. In the movie they were just sitting there, with nothing to hold them against the First Law. Contrary wise, the refrigerator had no inertia at all ….
At least how the water managed to avoid evaporation in the desert could be explained away by saying it was auto-filled when the firing sequence started.
As for her version of Russian, I kept waiting for Boris Badenov to show up.
3 CCPhysicist // May 27, 2008 at 5:58 pm
Again, I was too busy howling with laughter (inside) at the much bigger error with the nuclear explosion he was watching: it was the wrong color. It should have been violet inside the cloud, changing color as it cooled. After all, it isn’t fire that is inside the fireball.
At least they got the sequence right (ignition from the flash, followed by the shock wave) for the buildings - since they took it directly from the govt films - but forgot that the vehicle might have been in the line of sight as well, and that the driver would likely have been blind.
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