Hurry!! There are a lot of physics problems! Tell me if you know! 20 bounty!

1.In order for the liquid (mercury or alcohol) in the glass bubble to be heated evenly, the liquid expands sufficiently and the temperature can be measured correctly; 2.No; 3.

The transfer of heat to the liquid in the glass bubble is a process of expansion (or contraction) of the liquid; 4.Avoid changes in readings caused by temperature changes; 5.To avoid inaccurate readings; 6.

Utilization: hot air balloon (the density decreases after the thermal expansion of air) to prevent: leave a certain amount of gap between the railway rails to prevent the rail from bending and deforming after the rail is heated and expanded.

1。If all of them do not invade the liquid, the liquid in the glass bubble cannot all be subjected to the action of thermal expansion and contraction, and the temperature of the measured liquid cannot be correctly reflected.

2. First, the temperature of the liquid in the container is uneven, and the temperature of the wall and bottom of the container is slightly different due to heat transfer; Second, it is easy to damage the thermometer;

3. There is a process of changing the temperature of mercury in the cup just after entering the cup, and the correct data can not be read until the change stops;

4. If you take out the liquid thermometer and feel the temperature of the glass bubble, it is not the actual temperature of the liquid, and it may change;

5. There will be an indication error!

6. Advantageous: Thermal expansion and cold contraction can be used to make the metal parts assembly hole more compact on the shaft; Harmful: Freezing water in winter can break water pipes!

1. In order to be accurate, if only half of it is put in, half of it will absorb heat and half of it will be exothermic, and the problem of the surface of the water does not represent its internal problem, just as the body temperature of the person is the internal temperature and not the surface temperature.

2. Because the temperature of the wall is relatively low, the measurement is not accurate.

3. The liquid inside the thermometer (kerosene, mercury) absorbs heat and expands over time.

4. If you take out the reading, the thermometer will be exposed to the air, which will release heat, and the reading of the thermometer will decrease. However, it is not necessarily, the thermometer for measuring body temperature can be taken out and read, and the design problem, the thermometer will not automatically retract, and you have to throw it back by hand.

5. Because of the surface tension of the liquid, the surface of the liquid in the thermometer is not flat, but a concave surface, and the reading is different due to the different perspectives of people.

6. There are many such examples, utilized: thermometers, engines. Avoid: Railroad tracks

It's all about accurate readings and minimizing errors as much as possible

Thermometer The thermometer is the advantage of thermal expansion

Boiler Thermal Expansion, Dangerous Thermal expansion can deform and fail high-precision things.

1 I didn't learn. 2. I haven't learned. 3 didn't learn. 4 have not been studied. 5 didn't learn. 6 did not learn.

Question 1: 15 rails in the middle 15*25=375m v=s t=375 10=

Question 2 20 seconds passenger car running s=vt=

The truck was overtaken by 30 cars, which is 16*30=480m, so the truck drove 750-480=270m

Direct s=1 2at 2 substitution yields a=

Each track is l1 25 meters long, T1 10 seconds, T2 20 seconds, and each wagon car is L2 16 meters long.

Analysis: (1) From the time interval between the first and the 16th impact sound measured by passengers, it can be seen that the time taken by the passenger car to pass the distance of 15 railroad tracks is 10 seconds, so the speed of the passenger car is V passenger l1 t1 15*25 10 m s

2) Taking the passenger as a reference, then the truck is moving in a uniform and decelerating straight line with the muzzle velocity of V0 V passenger m s.

Derived from the title.

30*L2 V0 * T2 (A * T2 2 2), A is the acceleration of the truck.

Get 30*16 *20 2 2).

The magnitude of the truck acceleration is a m s 2

The resultant force of the two forces is 10-2=8n, and the object is at rest, indicating that the frictional force is greater than or equal to 8n

Remove 10N, it is still less than the friction force, so it still does not move.

Remove 2n, it's 10n, then it's just possible to move.

We know that the correct measurement method is the left object and the right code, m object = m weight + travel code.

Now it is the left code of the right object, then it can be known that the m code = m object + travel code.

So m thing = m code - game code =

1, DF=MA can find the traction force f and then the acceleration a1 can be obtained from a1=f m1

2,c two forces are in opposite directions, and the acceleration produced at this time is the smallest, 1m s2

The direction of the two forces is the same, and the acceleration produced at this time is maximum, 5m s2

Acceleration is possible in the range of 1m s2 ---5m s2.

d f=ma a=10 m=4000 so f=40000 when m becomes 3000, a=40000 3000=

c The resultant force of two forces is less than or equal to the sum of the two forces and greater than or equal to the difference between the two forces, i.e. the answer is between 3-2 and 3+2.

1.According to the pressure formula p=fs, we can know f=ps, so f=2The power formula p=w t knows that the power of useful work is fs t=3500*why not use 840 because it is the power of exothermics, not the power of the gasoline engine.

2.The output power of the car p=fv, f is the traction force of the car, this is a formula that illustrates the relationship between the power of the car and the traction force and the speed, so f=p v=63000 21=3000n

3.The useful power is 63kw, and the total power is the power for caloric combustion, so the power of the engine is: to the seventh power.

The WJQ6421 is finished. I don't have anything to say, it's complete, just give it to him.