Quote Originally Posted by 79blue View Post
To put to bed the argument about the effects of an impact at 30mph compared to 20mph we just need to go back to the basic physics. An object moving at a given velocity (speed) will have a kinetic energy (energy due to its mass and motion) as shown below:


Kinetic energy (in joules) = ˝ MV2 - where M = mass (kg) and V = velocity (m/s)

30 mph = 13.4 m/s (meters per second) - 20 mph = 8.9 m/s

Weight of average sized car = 1900kg


At 30 mph the kinetic energy of a car is:

0.5 x 1900 x (13.4 x 13.4) = 170,582 J


At 20mph the kinetic energy of a car is

0.5 x 1900 x (8.9 x 8.9) = 72,250 J


That is a percentage difference of 57.6%. Therefore a car striking a pedestrian at 30mph will have more than double the energy of a car travelling at 20mph. This is because the energy is dependant on the square of the speed.
My five year old Grandaughter knows that.

You must agree there were better needs for the money