The Question

Reading through Cracked.com's latest Photoplasty contest, I came across this graphic.

Why does this hapen?
This still applies to some modern video games.

Why do energy-based weapons in video games travel at a much lower velocity than bullets?

The Short Answer

Air resistance makes projectiles slow down.

The Long Answer

First of all, the bullets do not travel at an infinite speed, but at a speed that is too high for us too react in time. This applies to both video games and real life.

What are commonly thought of as pure-energy weapons in video games are usually not such, but instead are plasma weapons. Since plasmas are basically glorified gases, they will be affected by forces that would affect any other matter. Most other types of video-game weapons use either projectiles actually slower than bullets (such as arrows and boomerangs), or laser beams that travel at the speed of  light.

If the assumption is made that video games follow the same basic physics that the real world does, then projectiles coming from a gun of any type would be under the influence of at least two forces: gravity and air resistance. Other forces, though present, have relatively small effects on the motion of the projectile, so they can be ignored.

Air will make any object moving through it slow down, and is essentially dependent on the surface area of the object that is perpendicular to its direction of motion. The amount of force due to air resistance depends on, among other things, the speed of the object and the cross-sectional area of the object. along the direction of motion.

image
Plate 1 has a larger cross-sectional area, and therefore experiences more air resistance, than plate 2.

If we compare bullets to a bunch of plasma, we need to compare the surface areas and masses of both shots. For ease of analysis, let us assume that the masses of both projectiles are equal.

A bullet is solid, made of metal of a relatively high density; this makes its volume small. Furthermore, a bullet is designed to be as narrow as possible, minimizing the surface area exposed to air resistance. Furthermore, as it travels through the air, the bullet does not change shape.

Not even an apple can considerably slow down this bullet in this classic photograph. Air will barely slow the bullet down for the duration of its motion.

Simplifying a little, a plasma shot is composed of a ball of hot gas. Since the gas has a much lower density than the metal in the bullet, this gives it a much larger volume. This, combined with the spherical shape of the plasma ball, gives it a much larger surface area for air resistance to act on. Furthermore, a hot gas expands, so this will further increase the area of the ball, not to mention decrease its temperature and make it less effective.

Just like this smoke puff, the plasma ball starts off fast, then slows down considerably. It also moves and expands just like the description above.

Here is a side-by-side comparison of the forces on the two. For ease of analysis, assume that the plasma ball's radius increases by two radius values every 100 ms. Both projectiles leave the barrels at a speed of 800 ms-1.

Time/
ms
Air
Resistance on Bullet / Relative units
Velocity
of Bullet / ms-1
Air Resistance
on Plasma Projectile / Relative units
Velocity
of Plasma Projectile / ms-1
0 (release) 1.00 800 1.00  800
100 0.998 799  8.98  799
200 0.995 798 24.4  790
300 0.993 797 44.9  765
400 0.990 796 65.7  720

 

As can be seen in the table, the speed of the plasma ball decreases much faster than that speed of the bullet. Even with this simple example, it is now obvious why the plasma ball is easier to dodge; there is a drastic change in the speed of the projectile as compared to a bullet, over a small amount of time. From my calculations, at 1.18 s, the plasma ball should be almost at a standstill. Hence, plasma weapons are easier to dodge than bullets.

Applications

Many video games have physics equations ingrained in their code. This either makes the game realistic, or make it unnatural yet fun to play. These equations are based on real-life mathematical models of our daily life.

Final Thoughts

Energy-based weapons are actually either being used or under development. They all operate using either sound or electromagnetic waves such as microwaves. Both sound and electromagnetic waves (including light) move too fast for humans to react quickly enough, and both are invisible (light is only visible when it reaches the eye, and at that time it has already affected the target). Both weapon types are used to disable, rather than kill, targets.

Sources

  • http://www.cracked.com/photoplasty_841_29-baffling-rules-life-in-video-game-universes_p2/
  • http://i.crackedcdn.com/phpimages/photoshop/0/0/9/255009_v1.jpg
  • http://www.plasmacoalition.org/what.htm
  • http://en.wikipedia.org/wiki/Drag_(physics)
  • http://web.orange.co.uk/images/ice/news/bskyb_image_16129683_400x240.jpg
  • http://imgarcade.com/1/animated-smoke-gif-transparent/
  • http://en.wikipedia.org/wiki/Long_Range_Acoustic_Device
  • http://www.ausairpower.net/APA-DEW-HEL-Analysis.html