Ask two physics questions about pressure and buoyancy, and some physics questions about pressure and

The bottom area of the cylindrical container is 5 cubic centimeters, it can hold up to 160 grams of alcohol, if it is filled with water, find the pressure on the bottom.

The gravitational force of water g=

The container land area is s=5*10 -4

The pressure experienced at the bottom p=g s=

When a bicycle has a flat tire, the pressure and pressure change on the road surface during the driving process before the air leak is exhausted?

The pressure will gradually decrease, and the gravitational force will not change, i.e. the pressure on the ground f will not change.

The air leaks out gradually, and the contact area S becomes larger.

According to p=f s, the available pressure gradually decreases.

The base area is 5 cubic centimeters? If 5 is the bottom area, the volume of the container can be calculated by 160 grams of alcohol, and the height of the container can be calculated by dividing by meters, set to h, then the bottom pressure p= water gh after filling with water Because I don't know the density of alcohol, the landlord himself calculates the second question In the process of air leakage, because the area between the tire and the ground is gradually increasing (this is not difficult to imagine o( o...).While the pressure does not change (the mass of the leaking gas is ignored here because it is too small), the pressure decreases gradually by p=f s.

One. Solution: First calculate the volume of this container: the alcohol mass divided by the density of the alcohol, and the volume is 200 cubic centimeters.

The height of the container is then calculated: the volume is divided by the base area, and the height is 40 cm.

Then according to the pressure equal to the density (water) multiplied by g and then multiplied by the high, the pressure is equal to 3920 Pa. (g take cattle kilograms).

Two. Solution: The pressure remains the same, and the pressure decreases (just think about it, you can know that you have taken the test n times).

The buoyancy of an object is equal to the gravitational force of the liquid it distributes, and the destruction of the nucleus is the buoyancy of 15N carried by the object weighing 20N, and the net force is 5N downward, and the object sinks.

The pressure is only related to the density and depth of the liquid, because it is still water, and the density does not change; The height of the liquid level does not change, that is, the depth does not change, so the residual strength of the pressure does not change.

Spill 15 grams of water, if stupid can find out the volume of the object immersed in water.

This is where the assumptions are made:

Assuming that the total immersion is out, the density of the object can be calculated, and the result can be known when compared with the density of water.

Pressure problem: If you look at the container and the object as a whole, the pressure will definitely increase and the weight will increase.

The weight and volume of a 1D hollow ball are unknown, so it is impossible to judge.

2dBecause the amount of liquid poured is equal, the pressure on the bottom of the container is the same.

3aBecause the weight of the container is not counted, the pressure of the liquid on the bottom of the container is the same as the pressure of the container on the tabletop.

4. The weight of the object g = 300pa * 200cm 2 = 6n The mass of the object m = 6n g = 6

The density of the object p=m v=

1. Pick d can't be judged because neither buoyancy nor gravity can determine the magnitude.

2 choose a The bottom of the bottle is acted on by three forces in the vertical direction, the liquid pressure force f1 is downward, the elastic force of the support f2 = g liquid up and the force f3 perpendicular to the bottle wall, the third force is transmitted to the bottom of the bottle from the force of the liquid pressure on the bottle wall, when the container is wide and narrow, the direction of f3 is oblique downward, and the vertical component force f3'downward, f pressure = f2 + f3 'so f pressure > g liquid; When the container is narrow at the top and wide at the bottom, the direction of F3 is oblique upward, and the principle of F pressure 3 to C is the same as that of 2

4. The weight of the object g = 300pa * 200cm 2 = 6n The mass of the object m = 6n g = 6

The density of the object p=m v=

Weight refers to gravity, which is distinguished from mass, and g is not stated to be taken.

What is the atmospheric pressure on the mercury surface outside the tube when the top of the tube is 20cm above the mercury surface and inserted upside down in the mercury tank after filling a test tube with mercury at standard atmospheric pressure? What will I see if I make a small hole in the top of the tube?

Because it is uncertain how small the weight of the discharge is and how small it is, all three are possible;

The pressure exerted on the bottom is due to the gravity of the liquid, and the mass of the liquid is equal, so the pressure exerted on the bottom of the container is equal.

The pressure produced on the bottom of the container f1=ps= ghs, while the volume=sh, also has v=m, i.e., the pressure produced on the bottom of the container f1=mg. And there is only the effect of liquid gravity on the tabletop, i.e., f2 = mg, so there is f1 = f2.

4.Because the added pressure on the desktop after adding a block is equal to the gravity of the block, i.e. f=ps=300x200x10 (-4)=6n, then the mass of the block is m=f g=6. And the block density =m v=.

After correctly C is put into the ball, the height of the liquid level of the three containers is hc ha hc, so the pressure change of the liquid on the bottom surface of the container pc pa pb bottom area is the same, the pressure change of the liquid on the bottom surface of the container fc fa fb and for container a is a straight cylinder, fa=the gravity g g of the wooden ball has fc g fb

The pressure of the container on the table is the overall gravitational force, so fa = fb = fc = g

You can get fc fa= fa = fb = fc =g fb

The force on the bottom of the bottle is vertical, so the force on both sides of Figure B is also stressed, and the water height increases slowly. And c is also in the vertical direction (a straight cylinder with two corner vertices as vertical lines), and at the same time, the water height grows slowly and the force grows fast.

Correct is d, none of the above statements are true.

Because the same wooden ball is placed in the container, the increase of water on the pressure at the bottom of container a, b, and c is the weight of a wooden ball; The increase in the pressure of containers A, B, and C on the table top is the weight of a single pellet, which is the same as when a pellet is placed in three containers without water. Therefore, it is not possible to have any of A, B, or C.

(1) The candle in the beaker on the left burns, which consumes the oxygen in the beaker, and the pressure of the gas in the beaker decreases, while the beaker on the right is open, and the pressure is equal to the atmospheric pressure outside, so part of the water in the beaker on the right is pressed into the beaker on the left.

2) There are many examples in life. For example, when the doctor uses a needle to suck the medicine, when the piston in the syringe is pulled outward, the air pressure in the syringe decreases, and the medicine in the medicine bottle is pressed into the needle; In addition, when the piston of the inflator cylinder moves downward, the volume of gas in the cylinder decreases, and the pressure increases, so large that it is pressed into the belt when it is stronger than the gas pressure in the belt.

f=p*s;

The second question is that as long as you know that buoyancy is equal to gravity, you can calculate for yourself, how much gravity you can bear, plus the weight of the air cushion itself, hehe.

1. f=p*s=10^5pa * 1500*10^(-4)m2 =15000n=

Row = F float = 1 * 10 3 * g * v = 2 * 10 3n (2000n-30n) 700n =

Up to 2 people can be saved.

d Because A floats, B levitates. But it's all f float = g. And the two objects are exactly the same. So the buoyancy is equal.

f float = f down - f up. The upper surface of the nail is subjected to a liquid pressure of 0. The upper surface of B is subjected to the pressure of the liquid, so the pressure on the lower surface is greater than that of A.