Test analysis: (1) The gravity on the human body is G=mg=50kg× 10N/kg=500N. Because the whole body is at rest and in balance, the direction of f = f = g = 500N is vertical.
(2)f = PS = 1.0× 105 pa× 1.0× 10 ~ 3 m2×2 = 200n；
(3) Because G=500N and h=0.5m, W = GH = 500N× 0.5m = 250J.
So (1) when he hangs on the sucker (feet off the ground, regardless of the gravity of the sucker), the friction between the wall and the sucker is 500 n; The direction is vertical upward;
(2) The pressure of the suction cups on the wall is1.0×10.5 Pa, so the pressure of the two suction cups on the wall is 200 N;
(3) The work he did last time to overcome gravity by pull-ups was 250 J. Variant application; Calculation of work.