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The force perpendicular to the force surface is the pressure. The focus is on the vertical ... Even if the force is applied diagonally to the stressed surface, a vertical pressure can be obtained after the force is decomposed.

How does it happen??? This one... You give a force to the stressed surface. And it came into being.

Direction... I said it above. It's vertical.

Be careful not to confuse the concepts of vertical and vertical.

1 Definition: Pressure is the force of one object acting perpendicular to the surface of another object.

Concept: The force acting perpendicular to the surface of an object is called "pressure".

Direction: Perpendicular to the surface of the stressed object and pointing towards the stressed object.

Point of application: On the contact surface of the object.

Pressure & Effect:

1.When the pressure is constant, the smaller the force area, the more obvious the effect of pressure.

2.When the force area is constant, the greater the pressure, the more obvious the effect of pressure action.

Pressure and gravity[1].

1) Pressure is generated by the deformation of two objects in contact with each other when they are squeezed against each other; Gravity is created due to the attraction of the earth to objects near the ground.

2) The direction of the pressure does not have a fixed direction, but it is always perpendicular to the contact surface of the stressed object. Gravity has a fixed direction (because the contact surface may be horizontal, vertical or oblique) and is always straight down.

3) Pressure can be generated by gravity or it may not be related to gravity. When an object is placed on a horizontal plane and there is no other external force acting on it, the pressure is equal to the magnitude of gravity. When an object is placed on an inclined plane, the pressure is less than the gravitational force.

Force can deform an object. For example, if you squeeze the dough from all corners with a wooden stick, you can see that when the wooden stick leaves, the dough is left with pits, and the force that causes the dough to deform is pressure.

Many disciplines often refer to pressure as pressure, and pressure as total pressure. The pressure at this point does not represent a force, but rather a force acting perpendicular to the unit area of the object.

Unit. 1 megapascal (mpa) = 145 pounds inch2 (psi) = kilogram centimeter2 (kg cm2) = 10 bar (bar) = atmospheric pressure (at m).

1 lb inch2 (psi) = megapascals (mpa) = kilogram centimeter2 (kg cm2) = bar = atmospheric pressure (at m).

1 bar = megapascal (mpa) = pound inch 2 (psi) = kilogram centimeter 2 (kg cm2) = atmospheric pressure (at m).

1 Atmosphere (at m) = megapascals (mpa) = pounds inch2 (psi) = kilograms centimeter 2 (kg cm2) = bar (bar).

Formula for pressure:

Pressure = Pressure Area under compression.

pa=f/s

Let the time be ts1=8t

s2=2t*2/2

s1=s2 gives t=8s

When v1=v2, the distance is maximum, and t=4s, d=8x4-2x16, 2=16m

The second question may not be easy to understand, but you can draw an image (a time-velocity image or a time-displacement image).

Solution: If the ball is solid, the mass should be m1= v=, so it is hollow.

Missing mass δm = m1 - m0 = 790g - 700g = 90g hollow volume δv = δm = 90g

Answer: The hollow volume is.

There are several different ways to solve this problem, and it is necessary to change it according to the problem, in addition to mass, you can also use volume or average density).

Empty, if it is a solid m, it should be 790g

Assuming it's solid, its mass should be subtracting the actual 700, and there should be 90 grams of iron, and there is no 90 grams of iron, and that 90 grams of iron takes up space, which is 90 grams divided by about equal to, so the hollow volume is.

A series of sparse and dense waveforms are transmitted from left to right, and do not move to the right end, but only vibrate left and right, and the longitudinal waves are sparse and dense; During wave propagation, particles do not migrate with the wave.

1.When the globule M is at point C, there is mg = mv r

After the ball m leaves point C, it moves horizontally, and there is a horizontal distance between s=v*t, h+r=gt; 2m and m, x=s-r

If the above four formulas are combined, x = is obtained

and m, the mechanical energy is conserved, and there is mg *r 2-mgr = (m + m) v 2

And mg = mv r

Bring in: m:m=3:(1).

Idea: Before M lands, the mechanical energy of the system is conserved.

For m, it rises to the highest point, and the mechanical energy is conserved.

Find the highest point velocity.

This is followed by a flat toss.

This question examines the decomposition of forces.

In 2 phases:

Under the action of an external force f:

f'=f*cos（90-o）

The frictional force f=u*mg*coso, and the resultant force f1=f'-f, s1=f1*t*t (2m), velocity v=f1*t m when the force is withdrawn

There is no f under the effect:

After the external force is removed, the distance s2=l-s1=v1*t2-f*t*t (2m) needs to be traveledt2 is the requirement.