# Can someone help?

## Main Question or Discussion Point

I need someone's help. I have a personal math problem.I have tryed to do it myself but I am not very good at this. I was working as a diesel mechanic. A truck broke down on the freeway and I went to fix it. The truck weighed 80,000 lbs. I pulled my pick/up in front of it. It weighed 2,ooo lbs. The truck was 10 ft behind me at a 7% down grade. the driver of the truck released the parking brakes and got out. The truck rolled the 10 ft and pushed me and the pick/up 40 ft. I was in between the two. Can someone tell me how much impact the truck had on me. I do not know if it would be weight,mass,lbs per foot. I guess it would be total weight at impact.
If this is inappropriate for this site, I do apologize. I would just like to find out what impact the truck had on my body. Thank you for all your help.

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It is not possible to give an answer. The speed of the truck at me moment of impact depends on the friction, and is much less than the speed of an ideal no friction sliding or rolling object. The acceleration (and force) at the impact depends on how much you were deformed and the stiffness of the deformed part (belly, skull, etc.). On the other hand, if your pick-up was in the slope, the brake should be put-on. You could try to compute the force needed just to move your pick-up brakes on, but you must know the friction coefficient between the tires and the road. This is the only thing that can be estimated (just estimated). Assuming a friction coefficient of 1 (good tires, dry road) the force is near the weight of your pick-up, that is 2000 lbs. But the force at the impact should have been much larger. Did you survive?

russ_watters
Mentor
Yikes. That's rough.

I think the best you may be able to do is estimate the max possible force based on the slope and weight of the truck, which would be 7/100*80,000=5,600. That seems awfully high, though.