Can someone explain to me the physics of how those ski jumpers

They have quite some forward speed and they land on a downward hill, so if you look at it from the reference frame of the ski jumper, the ground is not approaching all that fast.

>>9095202
they're not landing on a horizontal surface, anon. the slope they land on is quite steep, so most of the energy from the freefall gets turned into downward motion instead of shattering their legs

>>9095243
>they're not landing on a horizontal surface

Some of them are

https://www.youtube.com/playlist?list=PLTR_peND6_mfJoyt5xEjJRLH7u77BshNw

>>9095202
By taking on a certain body position they make their bodies act a bit like an airfoil, exchanging vertical velocity for horizontal velocity.
https://www.youtube.com/watch?v=uVaev8pal-M#t=3m6s
Terminal velocity isn't a fixed value. It depends on the drag characteristics of the falling body. Ski jumpers try to maximize their lift induced drag.

They land on the back of the skis, and the skis flex to absorb some of the impact

Also they're landing on snow which is a bit yielding and helps absorb the impact, even though it's a bit packed on the ramp

>>9095262
none of those were landing on completely flat ground, they all hit in the elbow