Nerds go to movies for sheer entertainment - dissecting, criticizing, and arguing the merits of every detail of the movie. Some flaws they forgive, but serious scenes that completely neglect the laws of physics in very obvious ways are enough to make geeks vomit. Since its birth, Hollywood has generally been a disappointment as it continuously fails to guard itself against the evils of unacceptable physics.
Flashing bullets
The bad guy unleashes a burst of gunfire as the good guy and his girlfriend run along a walkway. Bullets bounce everywhere and we see bright flashes of light. A typical handgun bullet is made of copper-clad lead or lead alloys and it doesn’t create large sparks of light when it strikes objects.
Bullets have a static electric charge as they fly through the air. On impact, they cause parts of the target object to strike each other and produce bright flashes. In reality, however, flashes caused by typical bullets are definitely not as dramatic as the ones depicted in many movies.
Flaming cars
In Hollywood movies, expect that cars will burst into flames when they violently hit something. It’s as though the gas tank gets really scared and decides to detonate at the very thought of colliding with the wall, ground, or other cars.
Gasoline has a small flammable range of around 1.4% - 7.6% gasoline vapor in air. This means that the mixture of vapor and air must be precisely as specified otherwise it will not explode or even burn.
“Harmless” glass windows
Heroes and villains in Hollywood movies routinely drive through glass windows without slashing themselves. Broken glass windows involve the mechanisms of inertia and force for lacerating a person who dives, drives or jumps through a window.
When you drive a motorcycle through a window, glass shards stay in place because of their inertia. You can only move them by applying a force, which your body partly provides. This makes shards of glass slice right through your flesh.
Blowing the hero backwards
The good guy stands on the sidewalk munching on his burger when the bad guy across the street fires his shotgun. The shotgun blast blows the good guy off his feet and sends him flying two or three meters backward through a display window (often into a giant mirror, rack of whisky bottles, or some large glass object). However, the conservation of momentum rules that this can’t happen. A shotgun blast doesn’t have enough moment to propel a person violently backwards.
Outerspace explosions
Outerspace explosions don’t make any sound because the outerspace is a vacuum and there’s no air that enables the transmission of sound. When a distant explosion hit a space craft, it would sound like a wind blowing against the ship.
However, Hollywood filmmakers add sound effects to outerspace explosions due to market pressures. Even worse, they make it appear that sound travels at the speed of light, since it arrives at the same time as the image of the outerspace explosion.
