Experimental name: Factors affecting sliding friction Experimental purpose: To verify the relationship between sliding friction and pressure, contact area and roughness of contact surface (the experimental purpose of copying books, if DIS system is used, such purposes will sometimes be added, such as practicing linear fitting with DIS system and practicing stopwatch, etc. But these are not the main experimental purposes ~) experimental equipment: spring dynamometer, long board, cotton cloth, towel, hook cuboid wood. Experimental principle: 1. Conditions for the balance of two forces: If two forces acting on the same object are equal in magnitude and opposite in direction, and on the same straight line, then the two forces are balanced. 2. Under the action of the balancing force, the stationary object remains in a static state, and the moving object maintains a uniform linear motion state. 3. When two objects are in contact with each other, when they are in relative motion or have a tendency to be in relative motion, there will be a force on the contact surface that hinders the relative motion. This force is called friction. 4. When the spring dynamometer pulls the wood block to do uniform linear motion on the horizontal plane, the magnitude of the pulling force is equal to the magnitude of the friction force, and the value of the pulling force can be read from the spring dynamometer, thus measuring the friction force between the wood block and the horizontal plane. Experimental steps: Use a spring dynamometer to pull the wood block at a uniform speed to make it slide along the long board, so as to measure the friction between the wood block and the long board; Change the weight placed on the block, thus changing the pressure between the block and the long board; Spread cotton cloth on the long board to change the roughness of the contact surface; Change the contact surface between the wood block and the long board, thus changing the contact area. Experimental data: 1. Pull the wood block with a spring dynamometer at a uniform speed, and the friction between the wood block and the long board is measured at this time: 0.7N2 Add 50g weight to the wood block, and the friction between the wood block and the long board is measured at this time: 0.8n3 Add 200g weight to the wood block, and the friction between the wood block and the long board is measured at this time:1.2n4. Spread on the board. Measure the friction between the wood block and the long board at this time: 1. 1N 5. Speed up the speed of pulling the wood block at a uniform speed, and measure the friction between the wood block and the long board at this time: 0.7N6. Turn the wood block over, so that the other surface with a smaller area contacts the long board, and measure the friction between the wood block and the long board at this time: 0.7N (if Ohm's law is verified, the experimental data is given, and the drawing is made according to the data. Experimental conclusion: 1. The magnitude of friction is related to the pressure acting on the surface of an object. The greater the surface pressure, the greater the friction. 2. The magnitude of friction is related to the roughness of the contact surface. The rougher the contact surface, the greater the friction. 3. Friction has nothing to do with the contact area between objects. 4. The magnitude of friction has nothing to do with the speed of relative motion. On the Measurement of the Volume of Irregular Objects