Same impulse. But the collision with the wall is a stiff and snappy one: large F small Δt. Whereas the collision with the sheet is a soft and draggy one: small F large Δt. Nevertheless, the resulting Δp is exactly the same.
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Bending the knees upon landing lengthens the impact duration significantly, resulting in significantly smaller F. Do realize that the impulse is not reduced. It is just spread over a longer duration.
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Check out the timers at the bottom left corner. Notice how quickly the car body comes to a rest compared to the passenger. Air-bag or not, the impulses experienced by the the passenger are the same. But hitting the air bag is a lot less forceful than hitting the rigid steering wheel because of the longer impact duration.
xmPhysics 