Ezra Cornell, of Ithaca, New York State, USA, asks :-
In the film "The Bourne Identity" the hero, in a tight spot in a stairwell, grabbed the body of a dead baddy, jumped over the bannister and fell several stories, using the baddy's body to break his fall. Would this be possible?
John Campbell, a physicist at the University of Canterbury, responded.
It isn't the fall that kills, just the sudden stop at the end. As they say, dont try this at home.
Keep in mind that the stunt you saw in the film was filmed by Hollywood people. Stuntmen did the trick but it would be filmed in little pieces and put together to look like a long drop onto a hard floor.
What counts is the force on the body during the impact, ie the body's mass and the rate at which speed changes as the object comes to a halt.
I recall that after a long fall an elephant splatters, a human is crushed but a mouse walks away. That is because their final speed before impact depends on air friction. Parachutists in free fall will spread their arms and legs to slow down but tuck them up to fall faster. Before meeting the ground they deploy their parachute to slow them to a safe landing speed. The upwards frictional force on a mouse will balance the downwards gravitational force at a speed sufficiently low that it is like jumping from a small height.
For a fixed body we need to make longer the impact time when coming to a stop.
You may remember Jackie Chan (who does all his own film stunts) jumping from a multistorey building onto the canvas shades above each window. Each slowed him a bit as it ripped so he wasn't travelling too fast when he landed on the ground.
There was a case in the second world war when a Royal Air Force person chose to jump from a burning plane without a parachute rather than burn to death. By chance he landed in a forest and his fall was broken as he broke branches falling through a tree. He survived. During the same war the hard-pressed Russians experimented with troops dropping from low flying planes, without parachutes, into soft, deep, snow.
Stunt men and women doing high dives fall onto stacked cardboard boxes, or increasingly so these days, large bags of air from which the air escapes relatively slowly. I believe some people have survived falls from buildings by luckily falling onto the roof of cheap cars which cave in. Modern cars are especially made to slowly crumple during a head-on collision, increasing the time taken for the human body to come to rest.
I remember advice from my sea cadet days. When you have to jump into a lifeboat, always aim for the fattest person in it.
If all else fails when I was falling, would I grab hold of a baddie or a dead body? Yes. The trick is to fall side-by-side with arms and legs extended, to maximize air resistance and thus minimize the falling speed, but to land horizontally on top of the other body, so the crushing of its bones and collapsing of the body organs would increase the contact time, and with my vulnerable head in the baddy's soft stomach area. Would I survive? Probably not from a reasonable fall, but it would be the only chance I had to improve the odds.