From: Jerome (email@example.com)
Date: Thu Feb 21 2002 - 11:55:43 MST
Suppose I am stepping out of the seat of a high, stopped vehicle (a 3000
pound mini-van), which is stopped on ice.
Suppose, further, that I have placed one foot outside the van, on the
ground, and have begun standing on that leg, when:
The van I am climbing out of is struck from behind by a 4000 pound car
traveling at, say 35 miles per hour. The car striking the van comes to
rest, imparting it's energy to the van, which quickly comes up to a high
(~35 mph?) speed. Since my torso is still in the doorway, the rear leading
edge of the door frame strikes me in the back at whatever speed the car is
traveling, accelerating my 220 pound body like the blow from a giant hammer
(the impact zone between the door frame and my back being about 1 inch by 8
inches). Luckily for me, the impact was felt about 2 inches to the right
of my spine, so I was only badly hurt, but not paralyzed.
My physics question is: how does one characterize the energy transfer that
occurred here? I'm especially interested in being able to say how much
energy was in the blow that I received.
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