Why is an object resting on a level ground not subject to frictional force

To be precise, when an object moves or has a tendency to move on the surface of another object, a hindering force called friction will be generated at the contact surface of the two objects. For example:

A box on the floor, you push it hard, even if the box does not move, there is friction at this time, just because the friction at this time is equal to the force you push, so the box is not moving, you continue to exert force, when the force you use is greater than the friction, the box starts to move. Therefore, the generation of friction is related to whether the object is subjected to an external force. When an object is on an inclined surface, due to gravity, a sliding force is generated, and friction is present even if the object is not moving.

An object resting on a level ground is not subject to friction because it is not affected by external forces, and gravity is perpendicular downwards, and this object has neither motion nor tendency to move.

How can there be friction when it is stationary?

When an object moves on the surface of another object, a force called friction is generated at the contact surface of the two objects. For example, in daily life, the car driving on the highway depends on the friction between the car tires and the ground to move forward.

Friction is usually divided into sliding friction, rolling friction and static friction.

We know that the kicking out of the ball will slowly stop due to the frictional force. Pushing a car hard, without pushing, is also due to the action of friction. The brick-cutting performance also relies on friction to glue the bricks together one by one until they are glued in large stacks without falling off.

Friction, in the hands of an acrobat can create many wonderful sights. The pull force of the locomotive on the carriage** is the friction between the wheels of the train and the rails. When the wind blows across the sea, the friction of the wind on the sea surface and the pressure exerted by the wind on the windward side of the wave force the sea water to move forward, forming a wind current.

In the friction layer, the wind walks on the rough and uneven surface of the ground, and the wind speed has to be reduced due to the frictional force. Due to the different roughness of the surface, the degree of friction is different, and the degree of wind speed reduction is also different. In general, the friction on the land surface is greater than that on the sea surface; And the friction on the land surface, the mountains are larger than the plains, and the forests are larger than the grasslands.

Friction will not only weaken the wind speed, but also interfere with the wind direction, carpenters in the work of grinding the plank, is to use sandpaper on the board to rely on the friction generated by the sandpaper and the board to smooth the plank; The automobile engine relies on the friction with the belt to transmit kinetic energy to the generator to generate electricity; When people wash their hands, rub their hands to wash off the dust on their hands; The washing machine rotates when washing clothes, causing friction between clothes and water; Friction between teeth and food when eating; mop the floor with a mop; wipe the table with a cloth; Erasing the blackboard with a board will create friction. In our lives, friction is generated whenever objects come into contact with each other.

How to increase friction and reduce friction:

The magnitude of sliding friction is related to the positive pressure between the two objects and the surface condition of the two objects, the greater the pressure, the rougher the surface, and the greater the friction.

An object weighing 100N is stationary on a rough horizontal plane and is in a state of equilibrium, so the magnitude of friction is 0N;

When pushing an object with a horizontal thrust of 10N, the object is stationary and in equilibrium, and the frictional force at this time is 10N, and the direction is opposite to the thrust direction;

With a horizontal thrust of 30n to the right, the object just does a uniform linear motion, which belongs to the equilibrium state, so the two forces are equal, then the friction force is equal to the tensile force is equal to 30n, and the direction is opposite to the thrust direction, then the direction is horizontally to the left;

So the answer is: 0n; 10n；Contrary to thrust reversal; 30n；Horizontally to the left

When an object is at rest on a horizontal plane, the amount of friction experienced is zero so that it can remain stationary.

If you can carry it yourself, don't make a noise, your hypocritical and resentful appearance is not beautiful, be a brave person, learn to bear every slap that fate gives you.

This statement is false, there can also be friction between two objects that are relatively at rest – static friction.

1. There are generally two situations of friction: dynamic friction and static friction.

2. If there is an equal motion between two objects, then the force that hinders their relative motion is called kinetic friction.

3. If two objects remain static between them, but there is a relative tendency to move, there will also be friction, which is called static friction.

4. For example: "Push a table on the ground, but do not push", in this event, the table and the ground are relatively stationary, but there will actually be static friction between them.

Answer: An object subjected to static friction is not necessarily stationary.

Static friction: When an object moves on the surface of another object in the tangential direction of the contact surface or has a tendency to move relatively, a force will be generated between the contact surfaces of two objects that hinders their relative motion or the tendency of relative motion, and this force is called friction. If two objects are in contact with each other and squeezing each other, and the objects are relatively stationary, if they only have a relative sliding tendency under the action of external forces, but do not slide relatively, the force that prevents the relative sliding between their contact surfaces is called "static friction".

Not necessarily, static friction is only a description of the force exerted by the target object in a relatively stationary state with the object in contact with it, for example: an object is on a car, the car accelerates forward (the object does not move relative to the vehicle), in this process, the target object is subjected to static friction, but its state is in motion.

Static friction – the beginning of the universe.