Give you ① a holiday balloon, ② a wooden block, ③ a hook code, ④ a thin thread, ⑤ a spring dynamometer, ⑤ a plasticine and ⑤ many circles.

(1) Select ① ②. The method is as follows: put the wooden block on the balloon, horizontally and horizontally respectively, and observe the depression degree of the balloon; Explain the relationship between pressure and stress area;

(2) Selection: 234⑧ ⑧. The method is as follows: use a spring dynamometer to horizontally pull the wooden block on the table through a thin wire at a uniform speed, and read out the pulling force; Then put a heavy object on the block to increase the tension; The results show that the friction force increases with the increase of pressure.

(3) Select ⑤ ⑤. Practice: Weigh the gravity of plasticine with a spring dynamometer; Change the shape of plasticine and then weigh and compare; Explain that gravity does not change with the shape of the object;

(4) Select ③. Practice: After letting go, the hook code falls, indicating that gravity has changed the motion state of the hook code.