People who learn about almost any subject in detail will have the dubious pleasure of noticing all sorts of related errors in movies and television shows, often for the first time. Watching any sort of medical drama with a doctor or a nurse is always entertaining, since they’ll be picking out all the errors over and over again. Even the writers that put some effort into research are still going to make some mistakes.
Some of these mistakes are deliberate, since they need to be able to advance the plot of the story, and accurate physics isn’t always going to create a compelling plot. Some of these mistakes are so common within a given genre that generations of writers will make them over and over again, often without realizing that this is what they’re doing. In fact, many physics errors have actually become expected these days. The audience would notice an accurate portrayal because it would stand out from the pack, but this could prove to be too distracting for the audience. As such, writers will continue to create situations involving inaccurate physics simply because these situations have become necessities for the genre.
For one thing, scenes in which someone is thrown off a cliff into the water are common. Often times, the cliff is very high, and the water is fairly shallow. The audience tends to be under the impression that as long as the hero avoids the rocks, the hero is going to be fine. This misconception helps fuel the popularity of cliff diving, which is a very dangerous sport that people might avoid more often if they understood what was happening from a physics perspective.
Water is not actually soft. It has surface tension, which is why some lizards can effectively walk on water and why water isn’t entirely shapeless. Jumping thirty feet onto any surface is going to be more dangerous than jumping onto a surface that’s only three feet away. Leaping into water that’s thirty feet below one’s own feet isn’t so different from jumping from a cliff onto a hard surface. Cliff divers are skilled at breaking the surface tension of the water properly, but even they have a tendency to develop injuries. People thrown off the cliff into the water would probably break their spines or their necks in real life, drowning in the process or dying on contact.
Falls in general in the movies are nowhere near as dangerous as they should be for the hero or for the hero’s car. Heroes will drive through glass windows without being damaged by the glass shards that are supposedly there, which would act like knives in many cases. Heroes will somehow manage to convert helicopters to submarines, even though the design specifications of those two vehicles are completely different and they could not switch locations and jobs. However, the audience often won’t notice or care, since they’re engrossed in the plot.
Many writers may know about mistakes like this intuitively, but they may not fully take them into account when they’re devising their movie scenes. They have seen heroes get thrown into the water from a great distance on numerous occasions, and they may think that someone would have done something about it if there was a problem. The film fans that recognize these sorts of problems tend to get drowned out by the sorts of film fans who don’t care one way or another. Still though, these common physics mistakes can provide physics students and physicists some unexpected enjoyment along the way, since they’ll have fun pointing out the mistakes to themselves.