example for example a train that weighs kg moving at m s and that hits a 'perfect' steel wall where it uniformly decelerates from m s to m s in seconds has an approximate impact force of n thus a body which decelerates more quickly has a greater effective impact than one which decelerates more slowly i'm not doubting the calculation here but the example is a bit unusual meters per second is equivalent to about miles per hour faster than a bullet train and a kg train is like a toy train or something so in my head i'm imagining a toy train breaking the sound barrier and smashing into a steel wall i'm not sure what a typical train weighs maybe kg but apparently their max speed is about mph or km h or m s kg m s s n there doesn't that turn into a nice number