Why can t something with a small contact area stand?

The contact area is small, and there is also a center of gravity, as long as you can find the center of gravity, you can also stand.

Of course, finding the center of gravity of objects with a small contact area requires special techniques.

For objects with a large contact area, the center of gravity is easier to find because of the large support area.

As long as the sharpened end of the pencil finds the center of gravity, it can also stand, but it is more difficult, and the center of gravity at the other end is easy to find.

The center of gravity of the pencil is somewhere, and it is difficult to find the center of gravity when the contact area is small. The pressure is also high, so it is difficult to stand. The other end of the other side can stand.

In the case of high-speed spin, the pencil can also stand.

First of all, we need to understand the circumstances under which the object will fall.

Objects have a center of gravity and an area that is in contact with the ground, and when the center of gravity is in that area, the object doesn't fall over, but it falls down.

According to the principles of mechanics.

To make things stand or stand, you need to balance the support force and gravity, here the size of the force in equilibrium is generally not a problem, the direction of the force is relatively harsh, it must be in a straight line with the direction of gravity, the direction is opposite.

The support force generated by the contact surface should coincide with the direction of gravity, the direction of the support force and the contact surface are perpendicular, and the object will have a center of gravity and an area of contact, when the center of gravity is in this area, the object will not fall, but will fall on the contrary.

If a point or a line is used as a contact surface, because the point and line cannot determine the plane, it is difficult for the center of gravity of z to fall exactly on this point or this line, so it is difficult for the object to stand, and the smaller the contact surface, the more difficult it is for the center of gravity to fall into this contact surface, so it is more difficult to stand. This is why the three corners should form an equilateral triangle on the ground when building a tripod.

You first look in the clear water, if it is a white fluff that can float up, it is a fungal problem (water mildew, you can put it in the sun, or soak it in salt water for five minutes (5%), more solar energy prevention, if it is not white hair, it is a lump or punctate white corrosion, it is a bacterial problem (white spot disease, which needs to be anti-inflammatory, if you are raised in the water tank, you can put a cephalatin in the water tank.

For three days in a row, put three pills, and you can basically eliminate the bacteria on the white spots. If you need to prevent this, you should bask in the sun more to kill the bacteria and fungi on it, and the water should be fattened, not too thin or too clear.

The white color on the soft-shelled turtle may be due to mucormycosis, a disease infected by the mucormycomycete fungus.

The causative agent of this disease is the mucormycomycete fungus, which is transmitted through several routes such as water, feed, wounds, etc. This disease damages the soft-shelled turtle's ** and digestive tract, resulting in its loss of appetite, slow growth, listlessness and other symptoms.

**The method includes applying clotrimazole, soaking the soft-shelled turtle with 4% salt solution for 5 minutes or soaking the soft-shelled turtle with 4 milliliters of methylene blue solution for a long time, splashing the salt solution and baking soda solution mixed with the whole pool and splashing the sun** Put the soft-shelled turtle in the sun for 30-60 minutes, 1 time a day, repeat several times, the effect on the juvenile soft-shelled turtle in the early stage of the disease is better, or add 5 grams of vitamin E per 100 kg of soft-shelled turtle feed to feed, and use it for 15 days.

Brush it with a small brush first, if you can't brush it off, you are sick.

Divide the goods. Classes, layered placement, maximize the number of layers! Make the most of your walls. Use your brains more, things are man-made.

The frictional force is the product of the coefficient of sliding friction u and the supporting force given to the object by contact physics (plane of force).

u is definite, and if the problem involves pressure, then the net force in the perpendicular direction to the direction of motion is analyzed in relation to fn=ps, the supporting force.

If the problem does not involve pressure, only the force needs to be analyzed.

It doesn't matter, the pressure has something to do with the contact area.

f = fallacy mg

I can't beat it"Fallacy"The symbol of the --- said

It is also related to the roughness of the surface.

When I go to high school, I know that sliding friction f=uf u is the coefficient of friction, as the saying goes, rough is not rough f is pressure It has nothing to do with the area As long as the two measurements are determined, the friction is determined It has a relationship with the size of the contact surface There is pressure p=f s There is a capacitor in high school I am also a high school student Specific problems are analyzed.

When the contact area is the same, the greater the pressure, the greater the pressure.

When the pressure is the same, the smaller the contact area, the greater the pressure. p=f/s

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The pressure is directly used with the formula p=f s

Traction force does work is force x distance.

Because the efficiency is 30, the traction power is 30%, which is the energy released by gasoline combustion, and the heat removal value is the answer! I hope you forgive me for the hard work!!

...I saw that the question was almost the same, and I wanted to type out the answer. Outcome. Something is wrong, I found out, the topic is different. Brother, can't help.

LS is correct

In general, textbooks think it's irrelevant, and exams also think it's good if it's not closed1Two separate books, f=mgu (u is the coefficient of friction) but if the clamp, each contact surface will have its own friction, if the book has 100 pages, there are 398 friction (the upper and lower back covers are not forced), you can use f=nu to calculate (the list formula is also an equal difference series), so of course it is much larger.

2 Because the tensile force will have a radial component, the simple point is that there is pressure on the stake, so there is friction (because there is a tendency to move) and along the tangential direction, that is, the opposite direction of the tensile force, and the pressure is proportional to the tensile force, for a small angle, the amount of tensile force change is equal to the friction force in the end proportional to itself, after learning calculus, it can be strictly proved that the tensile force increases exponentially, so it can be pulled.

As for whether the friction is related to the area, macroscopically in terms of the ideal model, you can not consider the area, microscopically it is really difficult to say, when you really go to the actual situation, you will find that the situation described in the book is unrealizable, tired, over, I hope it will help you.

Chapter 7 Motion and ForceSection 6 "What is the magnitude of friction related to the student's experiment".

Problem 1: There is a molecular force cause (the books that do this experiment must be new).

2. The problem is more complicated, and that's because your pull is also converted into friction, so it's not easy to pull.