Crashing and falling

Today I saw a piece on 24 Horas about the danger of badly adjusted child car seats.

In the video a doctor explains that if a car crashes at 40 km/h, a child without a seat belt (or without a car seat) will be thrown forward, and the impact will be equivalent to a free fall from a 4-story building. The doctor then says that if the speed goes up to 80 km/h, the impact is as if the child fell from an 8-story building.

All of that information is terribly wrong, which is a shame.

I’m someone who is grateful to be alive, and I’m writing this thanks to the fact that I wear a seat belt; if I didn’t, I would have died on the highway a couple of years ago.

When you crash, what matters is kinetic energy, which is what your body carries, and which is proportional to the square of the vehicle’s speed. That means that if you double your speed, the kinetic energy quadruples! (two squared is four).

The other mistake the doctor in the TV piece makes is with the figures, because crashing at 50 km/h is equivalent to falling from a fourth floor. At 80 km/h it’s equivalent to falling from a tenth floor, at 100 km/h it’s like falling from the 16th floor, and at 120 km/h it’s like jumping from the 23rd floor!

Crash       Equivalent  
speed       to falling  
            from

50 km/h     4 floors

100 km/h    16 floors

120 km/h    23 floors

You wouldn’t throw your child from the 23rd floor, would you? Then make sure you use the right car seat for your kids, and of course wear your seat belt.