(1) The athlete's speed at point C = 10m/s,

The height that can rise from point C =? =5m .

(2) Let the speed when the athlete moves to the lowest point B of the circular trajectory be v2, and the speed when the athlete moves from to is:

? (2 points)

At the lowest point b, according to Newton's second law, F-mg=m,

Solution: f = 3000 n.

According to Newton's third law, the pressure of athletes on the runway is f' = f' = f = 3000 N.

(3) From point A to point B, according to the law of conservation of energy, athletes lose mechanical energy:

△E= =3000J .