"Stupid question that wandered into my mind earlier today. The saying "You mother wears Army Boots" is obviously an insult, but how did it come about, and what exactly is it supposed to convey?"
My impression was that it was accusing your target's mother of being manly. With the growing number of women in the armed forces, it's getting pretty dated, though.
"I'm explaining it badly, but maths not physics is my area sorry. I once heard a physicist break down the number of actual impacts in a car crash..."
This is true, but our discussion was about a particular collision and a particular injury, and that's where the description doesn't add up.
Mental Magpie wrote:
"Re: being independent from the car. I was using very general terms and wasn't clear. What I meant was that your body will eventually move from the crash. You won't just sit there while the car moves around you without ever moving you. For a split second while everything impacts everything else, sure, but in the end you'll move, too."
See above. There's no doubt that your body is going to get moved around by the collision, but I was questioning the concept of pressing the brake causing additional hip injuries, since perpetua argued that pressing the brake while stopped was going to do that. You're not going to suffer any more or any different injuries from a rear-end hit by pressing the brake than you would putting the car in neutral and putting your feet flat on the floor or holding them up, and if your foot is on the brake then post-collision your car is less likely to drift roll, so it's a good idea to press the brake firmly while you're sitting still.