Wednesday, August 27, 2003

Movie Physics
Stupid movie Physics

The vast majority of bullets are made of copper-clad lead. They simply don't create bright flashes of light when they strike objects

Gasoline has a very narrow flammable range of about 0.8 to 6% gasoline vapor in air. In other words, the vapor-air mixture must be exactly as specified or the gas will not burn, let alone explode! Note that we say vapor.

For a car to explode during impact the tank must catastrophically rupture and spew a fine mist of gasoline over a large area so it can vaporize and mix with air in exactly the right proportions. The mixture must then find a source of ignition. Automobile gas tanks are built to withstand a considerable impact force and are usually located in a protected area between the beams of a car's frame. Common ignition sources in the car's engine are generally at the other end of the vehicle.
Even when a wrecked car catches on fire it rarely explodes. A gas tank can explode if it contains an explosive mixture and there's an opening for the flames to enter.

A shattered window contains thousands of incredibly sharp edges and dagger-like points. It takes almost no force for one of these points or edges to cause a laceration. However, people in movies routinely jump through plate glass windows without receiving a single scratch.. In the real world, jumping or driving through a plate glass window would be suicidal.Laminated safety glass adds a thin layer of plastic sandwiched between glass layers. This helps keep pieces of broken glass from becoming projectiles

The general principle is that each additional meter of height is like adding the kinetic energy of another .45 cal bullet. Hence, a mere six-meter (19.8-foot) fall, which would be routine for an action hero, compares to being simultaneously shot by six .45 cal bullets, from a kinetic energy standpoint.bullets are incredibly lethal because they can easily penetrate into vital organs. A fall on a sidewalk would lack the penetration. However, it's pretty hard to completely avoid injury from being shot point blank six times with a .45 let alone 18 times, even when wearing a bulletproof vest.

Expanded objects or persons would have such low densities that they would be blown away in the wind like big balloons. Tiny people would suddenly exert huge pressures under their little feet since the area of their feet would be miniscule but their weight the same

Outerspace lasers are another matter. There's no air and few particles to make them visible. To make matters worse, some movies show laserbeams shooting through outerspace like glowing spears. All light, including laserlight, travels at 3×108 m/s or 186,000 mi/s (in a vacuum), so fast that the human eye couldn't possibly detect the motion of a laserbeam even if it were in the form of a glowing spear. The afterimage of the moving light source would make it appear as a continuous beam from the source to the target.

By contrast the movie has a scene in which the Hulk holds his love interest King-Cong-like in his fist. The Hulk would have to be at least ten times taller than his normal self to do so. If scaled up proportionally, the Hulk would be 1000 times more massive than his human form, but it gets worse. The comic book makers correctly gave the Hulk thicker legs and a more stout body. We say correctly because, like an elephant, he would need the thicker legs to support his increased mass. Unfortunately, increased stoutness means even more mass. The movie hulk would probably end up with at least 1500 times more mass than his human counterpart and a weight in excess of 100 tons ( 91,000 kg, assuming no density difference between hulk and human forms). Where is this mass supposed to come from?

In one scene the Hulk leaps up and grabs hold of a fighter aircraft. The Aircraft immediately heads for the stratosphere and shakes off the Hulk by causing him to pass out from lack of oxygen. Keep in mind that a fully loaded jet fighter weighs only about 15 tons. Even if we ignore the drag and other aerodynamic effects of having the hulk attached, we still have to wonder how a 15 ton aircraft can lift a 975 ton Hulk.

For example, the scale-up fallacy indicates that a strand of spider web scaled up by a factor of 100 would still be able to carry 50 times the spider's weight if it could carry 50 times the weight of a spider in its normal size. Unfortunately, it doesn't work that way. The scaled-up web will only be able to carry half the spider's weight even though the web material is still stronger than steel. The diameter of the web strand would have to be increased by a total factor of 10,000 not merely 100 in order to carry 50 times the oversized spider's weight.


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