v = ST = 16m 3.2s = 5m/s = 18km/h；
(2) The gravity of this classmate is:
G=mg=70kg× 10N/kg=700N，
The work done to overcome gravity is:
w = Gh = 700×( 1.8m- 1.8m×0.6)= 504j
(3) The pressure on the ground when students walk is
p = Fs = Gs = 700n 1.75× 10？ 2m2=4× 104Pa。
Answer: (1) His average speed in the run-up stage is18km/h;
(2) The work he did to overcome gravity in the high jump was about 504 J;
(3) When students walk, the pressure on the ground is 4× 104 Pa.