Reasons to drive slower (using physics)

The physics of moving objects certainly apply to your car, although the math varies greatly depending on the type of car you drive. The work a moving object does to overcome air resistance increases in a cubic relationship to increases in speed. This means that when speed doubles, air resistance increases by a factor of 8 (= 2^3). So it takes 8x more energy to push your car through air at 80 mph than it does at 40. That's 64x more energy than at 20 mph!

This explains why you should (where possible) keep your windows down in town but roll them up on the highway and use your air conditioning system instead.

Going faster is more dangerous because the the energy is a product of half its mass times its velocity squared (e = 1/2m * v^2). So if you double the speed, the energy that must be dissipated to stop increases by a factor of four (because velocity is squared).

So using the example above, your car has 4x more energy at 80 mph than it does at 40. That means your brakes are less effective if you have to slow down rapidly to avoid an accident and if you don't avoid it, your car will have to dissipate 4x the energy.

Loosely speaking, this means that 80 mph accidents are 16x more dangerous than accidents at 20 mph.

Related:

• More tips on saving gas
• Good things about higher gas prices