We know that the kicked football will stop slowly because of friction. Carpenters use the friction generated by sandpaper and wooden boards to polish wooden boards with sandpaper. Automobile engine transfers kinetic energy to generator to generate electricity through friction with belt; When people wash their hands, their hands rub to wash away the dust on their hands; The rotation of washing machine causes the friction between clothes and water when washing clothes; When eating, teeth rub against food; Wipe the floor with a mop; Wipe the table with a cloth; Rubbing the blackboard with a board will produce friction. In our life, as long as objects are in contact with each other, there is relative motion or a trend of relative motion, friction will be generated.
Two factors affecting the magnitude of friction:
1. Friction is related to the pressure between contact surfaces. When the roughness of the contact surface is constant, the greater the pressure, the greater the friction. In life, we have a common sense, that is, the tire is flat, and it is even more difficult to ride a bicycle.
2. The magnitude of friction is related to the roughness of the contact surface. When the pressure is constant, the rougher the contact surface, the greater the friction.
How to increase friction and reduce friction
1. The coarser the contact surface of an object, the greater the friction. Such as the pattern of soles and tires. When the car is driving on the road, the tire is in contact with the rough asphalt pavement, which will increase the friction. When the car is driving on the road with snow or water, the friction will be reduced. So pay attention to safety in rainy and snowy days.
2. Reduce the roughness between contact surfaces; The fan shaft should be smooth. Refueling the clock can reduce friction and make the time more accurate. In the skating rink, workers often clean the ice surface to make it smooth, which can reduce friction and speed up skating.
What is the tug of war? Many people will say: Of course it is better than which team! Actually, this question is not that simple.
Through the stress analysis of tug-of-war teams, we can know that as long as the pulling force is less than the maximum static friction with the ground, it will not be pulled. Therefore, increasing the friction with the ground has become the key to success. First of all, shoes with concave-convex soles can increase the friction coefficient and increase the friction force; In addition, the heavier the player's weight, the greater the pressure on the ground and the greater the friction. When adults and children tug of war, adults can easily win. The point is that adults are heavier than children.
In addition, in tug-of-war, the outcome depends largely on people's skills. For example, pedaling hard on the ground can exert more pressure on the ground than its own weight in a short time. Another example is that people lean back, using the pull of the other side to increase the pressure on the ground, and so on. Its purpose is to rub the soles of the feet to the maximum extent in order to win the game.
Through the above research and observation, it is concluded that the friction force depends on the pressure of two objects and the roughness of the surface.