The car and laws of nature

Speed and the increasing of speed

• The lateral force increases quadratically in curves. So if you increase your speed for instance by 3 times, then the lateral force will increase 3 x 3 = 9 times
• If you increase your speed from 40 km/h to 80 km/h, then the kinetic energy increases quadratically. So in this case you increase your speed by 2 times (which is 80 devided by 40), which means that the kinetic energy will increase 2 x 2 = 4 times
• The general rule of thumb is that when you increase your average speed by 10 km/h you save 1 minute per every 10 km you drive at speeds under 90 km/h. And if you drive over 90 km/h, then you'll safe about 0.5 minute (30 seconds) per every 10 km.
• When you want to convert m/s to km/h then you simply need to multiply the amount of m/s times 3.6.

So for instance 25 m/s = 25 x 3.6 = 90 km/h

And when you want to convert km/h to m/s then you simply need to divide the amount of km/h by 3.6.

So for instance 100 km/h = 100 / 3.6 = 27 m/s

• If you need to calculate approximately how many meters a car is traveling in seconds, based upon the speed it is in traveling in km/h, then you can use the following formula: (speed in km / 10) x 3 x amount of seconds
  Let’s say a car is traveling at 90 km/h and you need to know how many meters it is traveling in 5 seconds, then you calculate this with the formula; (90 / 10 = 9), then 9 x 3 = 27, then 27 x 5 = 135

Reaction time and reaction distance

• The reaction time refers to how fast a person himself or herself reacts, this is not at all related to for instance the condition of the vehicle­ nor tyres.
• The reaction distance is calculated by removing the 0 from the speed, then multiply with the reaction time, and then multiple by 3.This means that if you were driving at 70 km/h and your reaction time would be 2.5 seconds then your reaction distance would be; 7 x 2.5 x 3 = 52,5 metres
• One way to quickly find out which distance you should maintain to a vehicle in front of you on a country road, in order to react quickly when it would for instance brake suddenly, is by keeping the same amount of distance in meters as the speed you are driving. So if you for instance drive 90 km/h, you keep a distance of 90 metres.

Stopping distance and braking distance

• The braking distance is the distance a car moves after hitting the brakes to the point where the car comes to a standstill. The braking distance depends on the speed of the car, the state of the roads, the condition of the tyres and braking technique. The braking distance increases quadratically as the speed of the vehicle increases, which means that the braking distance and speed of the vehicle are directly proportional.
• The stopping distance (image 1) is the reaction time + braking distance. Let’s say you want to calculate the stopping distance and you know the current speed is 80 km/h and the reaction time of the driver is 1,5 seconds.
  The reaction time = The reaction distance is calculated by removing the 0 from the speed, then multiply with the reaction time, and then multiple by 3. So in this case it would be; 8 X 1,5 X 3 = 36 metres
  The braking distance = Speed divided by 10 X speed divided by 10 X 0,4. In this case it means 8 X 8 = 64 then 64 X 0,4 = about 25 metres

The stopping distance in this scenario will therefore be about 36 + 25 = 61 metres

Image 1: Stopping distance = reaction distance + breaking distance

• If your vehicle is for instance moving at 60 km/h and you know that the braking distance is for instance 40 meters at 90 km/h. Then you can calculate your own braking distance, but keep in mind that the stopping distance increases quadratically.

So in this case you first you divide; 90 / 60 = 1,5 This means that the braking distance will be 1,5 x 1,5 = 2,25 times greater, now you divide 40 / 2,25 = 17,8 metres