Tyrannosaurus rex may have known from experience not to run particularly fast because of the danger of tripping, in which case its short forearms would have been no help in cushioning the fall. Suppose a T. rex of mass m trips while walking, toppling over, with its center of mass falling freely a distance of 1.5 m. Then its center of mass descends an additional 0.30 m due to compression of its body and the ground.

(a) In multiples of the dinosaur's weight, what is the approximate magnitude of the average vertical force on the dinosaur during its collision with the ground (during the descent of 0.30 m) Now assume that the dinosaur is running at a speed of 19 m/s (fast) when it trips, falls to the ground, and then slides to a stop with a coefficient of kinetic friction of 0.6. Assume also that the average vertical force during the collision and sliding is that in

(a) What, approximately, are?

(b) The magnitude of the average total force on the dinosaur from the ground (again in multiples of its weight) and

(c) The sliding distance? The force magnitudes of (a) and

(b) Strongly suggest that the collision would injure the torso of the dinosaur. The head, which would fall farther, would suffer even greater injury.