Determine the direction of friction Many books explain that a bicycle moves at a uniform speed when it is stepped on by people, so the front wheels are subject to backward friction The front wheel does not rotate forward as the rear wheel does. Why is the rear wheel backward and the front wheel ahead? thank

Determine the direction of friction Many books explain that a bicycle moves at a uniform speed when it is stepped on by people, so the front wheels are subject to backward friction The front wheel does not rotate forward as the rear wheel does. Why is the rear wheel backward and the front wheel ahead? thank

The rear wheel is the driving wheel and the front wheel is the driven wheel. Assuming that the ground is smooth (assuming here, you should have the ability to think). Then you will see that the car is stationary, and the rear wheel rotates in place and the front wheel does not move. At this time, you will see the difference between the two. Then you can explain it by hindering the movement of the object. You can judge that the rear wheel is forward and the front wheel is backward

How to judge the direction of friction

Friction always tries to stop motion
Dynamic friction is opposite to the direction of relative motion, and static friction is opposite to the direction of motion trend

How to understand the direction of friction? Direction of friction: along the tangent direction of the contact surface, it is opposite to the direction of the object's relative motion or relative motion trend, and can be the same or opposite to the direction of the object's motion

Friction acts through the contact surface
Therefore, the research on it can focus on the contact surface
Friction will occur when the contact surface has actual relative motion or movement trend
Friction is a force that hinders the movement of the contact surface. Note that it is not a force that hinders the movement of an object
When there is a slip, the direction of friction is easy to understand
When you press a piece of wood against the wall, other pieces of wood tend to fall down, so a friction force will be generated to keep it from falling
The direction of friction and the direction of motion of the object
When all parts of an object move in the same direction, the friction force is opposite to its action direction, such as sliding in a plane
When the overall movement direction of the object is opposite to the relative movement direction of the contact surface, the friction force is the same as the movement direction of the object. For example, when riding a bicycle, the wheel rolls on the ground and the wheel rolls to the left. At that time, the movement direction of each point of the wheel is different, and the contact surface tends to move to the right to the ground, so the ground gives the wheel contact surface a left force, which is the same as the forward direction of the wheel

What kind of friction do people suffer when walking? Direction? analysis?

Let me answer. The meaning of friction is that two objects in contact with each other will produce friction on the contact surface when they have relative motion or have relative motion trend. The force that hinders relative motion or relative motion trend generated by this friction is friction. Friction is divided into static friction and dynamic friction, in which dynamic friction

What are the types of friction?

Friction is divided into (static friction) and (dynamic friction); Dynamic friction is divided into (sliding friction) and (rolling friction)

How to determine the direction of friction in a simple way?

The direction of friction force is opposite to the sliding direction or the direction of external force. Friction is caused by external force. Therefore, It should be judged according to the action mode of external force: first, the direction of friction in sliding or with sliding trend is opposite to the sliding direction or the action direction of external force. Second, the friction in rolling is opposite to the rolling direction. When judging with the rotation center as the balance center, when the action line of external force passes through the rotation center, the direction of friction is opposite to the rolling direction; When the external force is torque or couple, the direction of friction is the same as the rolling direction. 2. When the rolling instantaneous center is used as the balance center, the direction of friction is opposite to the rolling direction when the external force is torque; When the external force acts as a couple, the direction of friction is the same as the rolling direction. 3. Rolling is a composite motion of translation and rotation. Therefore, when judged according to the composite mode, the direction of friction caused by translation is opposite to the rolling direction; The direction of friction caused by rotation is the same as that of rolling. Note: the above judgment can be applied reversely. We can often contact friction in daily life. For example, the bottle and brush in hand will not slip, which is the result of static friction; There are also many applications in production technology. For example, belt conveyor transmits goods by static friction between goods and conveyor belt. Here are two common physical phenomena