When a person walks at a constant speed, what is the force that balances the friction of the ground

On the first floor, it is not correct to say that "the force of the human foot pushing backward on the ground is its balancing force", this force is the force on the ground, and the friction force mentioned in the title is the force experienced by the human foot. How do you balance two forces that are not on the same object?

Walking is actually a very complicated process. Starting from the first step, the person is originally stationary, and the back foot is on the ground, so the ground gives the back foot a forward static friction, so that the person can accelerate forward, and at the same time the center of gravity moves forward.

However, because the ground is not smooth, people will be subjected to frictional resistance given by the ground when they move forward (otherwise, as long as they start, they will keep sliding forward, and there is no need to continue walking), and this is still static friction (because people's feet do not slip on the ground). When the person is hindered by this static friction, the speed decreases, so the person needs to take a second step to repeat the acceleration process above.

Therefore, it is said that people move forward repeatedly accelerating, decelerating, accelerating, decelerating... It's not always doing uniform linear motion. Under what circumstances can it be said that people move at a uniform pace? Unless the person is subjected to a forward force and glides forward on a smooth horizontal surface.

If we have to look at it as a whole, then the two forces that balance each other are the static friction that makes people move forward and the static friction that hinders people from moving forward. But in fact, these two static friction forces appear in sequence, so they cannot be said to be a pair of balanced forces.

Analysis of the force on the human foot The human foot receives the backward pushing force of the limb on it The friction force of the ground on the foot Uniform motion The balance of the two forces.

If the whole person is regarded as a whole, the power is the reaction force of the ground to the back pedal; Resistance is the frictional force and the reaction force of the ground to the step.

Water 2 square 6 upward U uniform 3 speed forward, vertical square 3 upward j stationary 0, that is, do uniform 4 speed linear motion, the resultant force i is 80.

When people walk, they are in contact with the ground, and when they are on the ground, they squeeze on the ground, and the friction between the feet and the ground, with the ground as a reference, and the direction of the feet is backwards, that is, the feet have a tendency to move backwards, so the friction of the feet is forward, and the people move forward under the action of this force.

The "four-step method" for determining the direction of friction is as follows:

1. Find out the object of friction.

2. Select the force object as the reference object.

3. Judge the relative direction of motion or the relative trend direction of the stressed object.

4. Use "opposite" to determine the direction of friction.

The direction of the frictional force must be opposite to the direction of the relative motion of the object or the relative trend of motion:

For example, if an object is moving in a circular motion on a disk, the frictional force experienced by it is perpendicular to the direction of motion, but the direction of friction is opposite to the direction of the relative motion trend of the object and the disk.

There are three types of friction: static friction, rolling friction, and sliding friction. When an object slides on the surface of another object, friction occurs between the contact surfaces that hinders their relative motion, which is called sliding friction. The magnitude of sliding friction is related to the magnitude of the roughness of the contact surface and the magnitude of the pressure.

The greater the pressure, the rougher the contact surface of the object, and the greater the sliding friction generated.

Friction is a relatively troublesome force in mechanics because it has a lot of content and a wide range in the college entrance examination. Through visual examples, we can understand the method of judging the direction of friction and the calculation of size.

Pay attention to the process of walking first: the moment when the front foot lands (stabilizes the center of gravity) and the back foot lands on the ground. Walking is the process that repeats itself over and over again.

Front feet: only affected by gravity and support.

Hind foot: gravity (the vertical downward force of attraction received by the center of the earth), the support force, the friction force of the ground against the foot forward (where the person is provided with the power to walk).

Note the backward climbing force of the foot on the ground, which cannot be analyzed here because the object on which he is subjected is the ground and not the person.

In general, air resistance is ignored here, and the person is treated as a whole) i.e. by gravity, support, friction (forward).

When a person walks in front of the Ant Yuanchun, the direction of friction is (). Stuffy.

a.Back. b.Forward.

c.Pure left to the split.

d.Rightward. Correct answer: B

Friction has a lot of content and a wide range in the college entrance examination, and it is a relatively troublesome force in mechanics. Through the example of the image, we can understand the method of judging the direction of friction and the method of calculating the size of the bridge.

Answer: Analysis:

When people walk forward, people's feet kick the ground after shouting, that is, the feet that imitate the ground have a tendency to move backwards relative to the ground, so the friction of the ground facing the feet is forward, and in this case, the friction plays a role in powering people

When a person is walking, the friction between the shoe and the ground is static friction. The static friction of the ground against the shoe is in the direction of forward, and the effect is to prevent the shoe from slipping backwards so that the person can walk.

When a person suddenly stops walking, the direction of the static friction force on the ground against the shoe is backward, and the effect is to prevent the person and the shoe from sliding forward, so that the person can stop.

People are prone to slipping when walking on ice, and when slipping, the friction between the shoe and the ice surface is sliding friction. However, the direction is still the same as the above method.