Physics Olympiad Questions, Physics Competition Questions.

I'm also a junior high school student, and I've done this pressure question, which is my comprehension and solution:

Solution: Let there be a liquid sheet K in AB that is level with the water surface of C, and we can know that the pressure of the gas (atmosphere) and liquid above K is equal to the pressure of the CGD gas on the liquid level of C, then let the pressure of the closed gas in CGD be P, and the atmospheric pressure is P0, then P P0 P liquid, and the depth of the liquid sheet K is H1 H2 18cm 2cm=16cm, so K is subjected to the pressure of the liquid above P liquid GδH 1 10 3 Atmosphere P0 101300OPA, then the pressure of the cgd closed gas is P P0 P liquid 102868pa

Hello, I'll answer your questions for you. I hope you can understand after watching the process.

If the liquid sheet K in AB is equal to the water surface of C, then the pressure of K on the gas and liquid is equal to the pressure of CGD gas on the C liquid level. Let the pressure of the enclosed gas in CGD be p and the atmospheric pressure is p0, then p p0 p liquid. If the depth of the liquid sheet K is H1 H2 18cm 2cm=16cm, then K is subjected to the pressure of the liquid above P liquid GδH 1 10 3 atmosphere pressure P0 101300OPA, and the pressure of CGD sealing gas is P P0 P liquid 102868Pa

Note: Indicates to the power of the power.

The other two are the frictional heat and the incomplete combustion of the fuel residue of the chemical energy rubber car.

Let the efficiency be x, beam.

p*t=q*ρ*v* x

The above calculations must be converted to standard units.

If you don't understand, you can ask me again.

Frictional heat can also refer to a type of heat energy that has not been searched. It should be the chemical energy emitted by the combustion of gasoline, and the heat energy of incomplete combustion. The equation is the same as his, and the efficiency is x, p*t=q* *v* x

Because u'>>u, the problem requires the maximum distance that can be moved, obviously when the friction between the plate and the ground is negligible, that is, the resistance is the smallest when u->0, and the maximum can be reached, at this time, the momentum of the person and the plate system is conserved, due to the initial stationation, the plate is also approximately stationary when the person stops at the end, and the position of the center of mass of the system at the beginning and end is unchanged.

The initial system centroid is located at a distance of one side from the human side.

m/(m+m)*l/2

At the end of the system, the distance between the centroid of the system and the side (now the side where there is no one) is l-m (m+m)*l 2

Since the centroid does not change, the distance traveled at one end of the plate is the distance traveled by the plate, i.e., [l-m (m+m)*l 2]-m (m+m)*l 2=ml (m+m).

The calorific value of diesel should be 10 7J kg1, the lowest fuel consumption corresponds to the highest efficiency, providing 1kwh (i.e. 240g of diesel fuel is required for useful work, and the total energy released by diesel combustion according to the calorific value of diesel fuel is , then the efficiency is.

There are 2300 strokes in min, the total work done by 6 cylinders is 220kw*60s=, the gas to piston thrust is ps, and the work done by one stroke is psl, then 6psl*2300=, and the algebra is p=

31% = (3-x) 35%, which can save x = 100 million tons.

4. Save funds of 375 billion = 100 million yuan.

Addendum: You can check the information, the calorific value of diesel fuel can not be 10 J kg, even if different types of diesel have different calorific value, it is impossible to be 6 orders of magnitude worse, according to this calculation, 240g of diesel can only produce energy, and not to say that it does not conform to the actual situation (in fact, if this is the case, it is estimated that no one will use diesel, because the fuel tank does not know how big, and the energy generated by diesel combustion is estimated to be unable to overcome the resistance caused by its own weight), and it cannot be explained only from the perspective of energy conservation, Because the energy generated by the combustion of 1kg of diesel fuel in 43J suddenly became!

In this case, even if the brake is abrupt, the speed of the two sides remains the same due to inertia, but the frictional force produces it, but the acceleration caused by the frictional force is still the same. So the state of motion is exactly the same, so d is right.

The so-called large inertia means that if it is necessary to change the speed of the object in the same time, the force required for the inertia is greater.

For example, when an object with a mass of 1 ton is moving at a certain speed, the frictional resistance required to stop it within 1 second = the product of mass and acceleration, and the same is true for an object of 1 gram. The acceleration is the same, the greater the mass, the greater the frictional resistance, that is, it is more laborious to change the motion state of a large mass object than to change a small object, that is, the inertia of a large mass object is large.

a=f m=mg m=g, which is not related to weight.

Only the kinetic energy problem is involved, the initial velocity of the large and small objects is the same, assuming that the contact surface between the object and the car is ideally smooth, and D is correct. If there is friction, inertia needs to be taken into account.

lz should know: inertia is not a quantitative, just a qualitative property, or there is no unit, so the cow must only be used to judge, when doing this kind of question, it is necessary to combine the ox two, this question is an instantaneous problem, and the speed has not had time to change.

This question doesn't make much sense, and in fact, the value of s is not discussed.

If the two cars start to move in the same direction, then a1>=v1 2 (2(s+v2 2 2a2)), there is no need to specify the size of s;

If the two cars start to move in opposite directions, then a1>=v1 2 (2(s-v2 2 2a2)), at this time the s condition: s>v2 2 (2a2), if s=v2 2 (2a2), theoretically, the length of the train is not included in s, and a1 = infinity, at this time the two cars just touch the front of the car, it is not considered a collision, but the actual does not match, in addition, if s explains a point, the a1 given above is all absolute value conditions, the direction is opposite to the train speed v1, of course, a2 is also a value.

There's no need to wait any longer, it's definitely true, but it's a bit of a surprise to me that it's a competition question. The process is not difficult, draw a picture by yourself, and the normal level will come out as soon as you are high.

It is solved according to 2as=v*v. So a1=((v1*v1) 2) (s-v2*v2 2a2).

Therefore, it is divided into three cases: a1 is greater than = less than ((v1*v1) 2) (s-v2*v2 2a2).

How big is the acceleration a at least to avoid the collision of the two cars, that is, I want to think that the two cars just collide.

It can be found that the distance that the previous train will travel is x=-v2*v2 2a2.

The latter train just collided, which is the distance traveled x+s. Obtainable.

a=-v1*v1 (2(s-v2*v2 2a2)) means that a should be at least that big.

Level 24. Solve Process:

Set, the exposed number of steps is n, the customer customer walks upstairs along the escalator, and counts the time required to walk 16 steps t, then in t time, the electric imitation round ladder goes up (letter stool n-16) steps, when he uses the same speed relative to the escalator to start the escalator downwards to go upstairs, he has to go to the preparation of 48 steps, the time taken should be 3t, because the elevator speed is unchanged, therefore, the elevator disappears down 3 (n-16) steps. And if a person wants to go up the stairs, he should have, 48-3(n-16)=n, and the solution is n=24.