There are often climbing ropes and sliding bars on the physical education class. Xiao Ming and Xiao Hua, who are equal in weight, want to see who can climb the pole faster. Why should they go in the d

There are often climbing ropes and sliding bars on the physical education class. Xiao Ming and Xiao Hua, who are equal in weight, want to see who can climb the pole faster. Why should they go in the direction of friction? Friction can also be said to be the force that stops you from slipping. In the process of climbing rope and sliding bar, downward gravity will be generated because of its own weight. In order not to slide down, friction will be generated, that is, the force borne by friction = downward gravity. Gravity is downward. In order to keep people in balance, the force generated by friction is upward. It's the same when riding a bike. If the car goes up, the direction of friction is the forward direction (climbing trend), and the friction is downward when braking. If you want to know the generation of friction, you can let a book push it forward on a flat plate. Think about what has stopped the book from moving forward. Uphill, flat slope and downhill slope have different friction directions. )