1. 1. Guess: Friction is related to the speed of an object.

2. Experiment: (1) Put the selected wood block on a horizontal long board, and use a spring dynamometer to pull the wood block in a straight line at a uniform horizontal speed, and read the indicated value of the spring dynamometer as F 1.

(2) Repeat step (1), only increase the uniform speed, and read the indicator of the spring dynamometer as F2.

(3) Compare the size of F 1 and F2, and draw a conclusion.

3. Conclusion: Friction has nothing to do with the speed of the object.

Second, 1. Guess: Friction is related to the contact area of an object.

2. Experiment: (1) Put the selected wood block on a horizontal long board, and use a spring dynamometer to pull the wood block in a straight line at a uniform horizontal speed, and read the indicated value of the spring dynamometer as F 1.

(2) Repeat step (1) except that the board is placed on the long board, and the reading of the spring dynamometer is F2.

(3) Compare the size of F 1 and F2, and draw a conclusion.

3. Conclusion: Friction has nothing to do with the contact area of objects.

3. 1. Guess: Friction is related to the roughness of the object contact area.

2. Experiment: (1) Put the selected wood block on a horizontal long board, and use a spring dynamometer to pull the wood block in a straight line at a uniform horizontal speed, and read the indicated value of the spring dynamometer as F 1.

(2) Repeat step (1), only put the wood block on the towel, and read the reading of the spring dynamometer as F2.

(3) Compare the size of F 1 and F2, and draw a conclusion.

3. Conclusion: Friction is related to the contact area of objects.

4. 1. Guess: Friction is related to the pressure on the object.

2. Experiment: (1) Put the selected wood block on a horizontal long board, and use a spring dynamometer to pull the wood block in a straight line at a uniform horizontal speed, and read the indicated value of the spring dynamometer as F 1.

(2) Repeat step (1), only put a hook code on the block, and read the indicated value of the spring dynamometer as F2.

(3) Compare the size of F 1 and F2, and draw a conclusion.

3. Conclusion: Friction is related to the pressure on the object.

So: Friction is related to the contact area of an object.

Friction is related to the pressure on an object.

Friction is related to the roughness of the contact area of the object.