Calculating Force of Impact...

RobG

RobG

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I had a thought this morning. Gruesome, but put that part out of your mind and it's really kind of intriguing.

Let's say somebody on a sportbike similar to an FZ1, total weight of 650 lbs (bike plus rider), was going WOT at 150 mph on a straight road, and met an unfortunate end by hitting a Semi head-on, which was going towards him at 60 mph and weighing in at 80,000 lbs.

I'm trying to calculate the force with which the bike would hit, and I'm also wondering what impact (no pun intended) it would have on the truck. Granted there'd be lots of damage, but how much? Would it force the truck off the road? That sort of thing.

Since I never had a physics or calculus class, I have very little clue how to go about this. I did some Googling, and the only number I came up with, which may not even be accurate, is that the force of impact would be the equivalent of approx 20 MILLION foot-pounds of torque.

It also reminds me of the Reno Air Races last year, where that pilot plowed into the ground at about 200-250 mph (maybe more) in his vintage plane. I don't think there was much left of the plane, at least that was identifiable. I know it left a small crater in the pavement... basically a greasy spot. I have family in Reno so I heard lots about it... even made it out to the Stead Airport and was within a hundred yards or so of the impact zone for an autocross event. It was fenced off and covered.

Thoughts?

Rob
 
Yeah that's the sort of thing I'm wondering... and I agree with you. I'm inclined to think it'd rip the motor clear out of the truck, or if it hit square enough, drive it through the firewall into the cab. And to think the motors in those things weigh upwards of 2000 lbs.

Rob
 
Google "conservation of momentum".

If I recall

Energy = mass * velocity * velocity

Truck = 80000 * 60 * 60 = 384,000,000

bike = 650 * 150 * 150 = 14,625,000

Truck has 26 times as much energy
 
Its kinetic energy. Truck traveling towards the bike, add the energy together.

Kinetic energy = 1/2 x Mass x Velocity^2

So its 309,760,000 for the truck plus 15,730,000 for the bike.


Thats 240M joules. Burning one gallon of gas consumes 131M joules. So to equal the energy of the impact, blow up two gallons.
 
I don't know in terms of numbers how much the force of impact would be. It would be catastrophic but I strongly doubt the motor would be ripped from the truck or pushed into the firewall. I build those type of trucks but I can only guess as to the damage. I would imagine from the height of the truck most of the impact would be to the front of the frame. My guess would be frame damage in the front, obviously damage to the cab from the debris of the bike but the motor isn't going anywhere. It would be interesting to see what would be left of the bike though
 
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