I decided to find the force exerted onto Antonio Brown by the goalpost. I started my analysis of this celebration by finding Brown's speed before his goalpost collision. I approximated this as his average velocity as he ran through the end zone (10 yards).
v = ∆x/∆t = (10 yards) / (19 s-17.5 s) x (0.91 m) / (1 yard) = 5.7 m/s
Then, I used this to calculate Brown's momentum before the collision:
(Antonio Brown's mass: 82 kg)
p = mv = 82 kg x 5.7 m/s = 467.4 kgm/s
Then, I used his momentum and the time of the collision to calculate the force:
Time of collision: 0.2 s
∆p = -467.4 kgm/s (Brown and the goalpost combined have a momentum of 0 after the collision) = F∆t = F(0.2 s)
F = -2337 N = 525 lb
Thus, Brown felt considerable force during this collision. It likely would have been very painful.