Junior 2 Physics Answers Expedited Expedited Thank you Thank you

Set the time to x seconds.

x=Hope this helps.

The crux of the problem is that when the correspondent runs to the front of the group, he moves the same amount of time as the whole team. Prompt you to make it yourself more profoundly.

This can be seen as a catch-up problem, v1=, v2=, s=250m

Using the catch-up formula, (v1-v2)t=s to obtain t=100s

Correspondent distance s=v1*t=

This question is simple, first use it as the relative speed, 250, that is, the correspondent ran 100s this is the time before catching up with the team, 250 5=50s this is the time to run to the end of the team, then the correspondent ran a total of 150s 150*

Mine is correct, the explanation is detailed, hehe.

Solution: s=t v=250m

Time is certain, multiply 200s by 2 = 1500 meters.

The reflection symmetry point about the water surface S is the position of the wall lamp S (plane mirror imaging), the perpendicular line from the O point (remember to use the dotted line) is the normal, and then connect the line from the goldfish to the O between the normal and the reverse extension line of OA, and mark the arrow. I can't upload the picture, I'm sorry I don't know if I can understand it.

One is placed every 5 km, the distance is 50 km, and the monuments that need to be placed are 11 (50 5 + 1 = 11).

Parking time is 11* minutes.

The time to reach the opposite side is 50km 50km h = 1 hour. The total time is 1 hour and 1 minute.

There are minutes left to get back. The distance is 50km.

So the return speed is 50.

Put a roadmark every 5km, then a total of 50 5 + 1 = 11, if the middle does not stop, then the time required is 50 50 = 1 hour, each drop point to stop for minutes, then a total of 11 * minutes, then put a total of 1 hour to finish the roadmark. The remaining time is minutes, about hours, and the speed is 50

The time it takes for the car to complete 50km in 50km, plus the time to reach milestones at the drop point (t = minutes * number of milestones set), plus the time for the car to return (assuming t).

The sum of the above three times equals 2 hours.

Then solve the unary equation.

In the process of solving the problem, it is necessary to pay attention to the conversion of units, such as minutes into hours.

The number of milestones,The number of drawings in your own notebook.,Now that you already know the standard answer.,Look at the number of milestones according to the answer.,And then figure out why there are so many milestones.,After pondering clearly.,In the future, similar topics will be like this.。。。

However, the title is not good, it does not clearly state "whether there are milestones at both ends of the road" (it is not bad to say that it has 10 milestones, to say that there are 11 milestones is to say that it is in the past, and it is okay to say that it has 9 milestones).

50km away. Put one in 5km, a total of ten.

In the past tense, the shared time is 1 hour + minutes * 10 = 75 minutes, so there are still 45 minutes left to come back, i.e., the speed of coming back is (50, 45), 60=

The object distance becomes larger, the image distance becomes smaller, and the image becomes smaller.

The object distance becomes smaller, the image distance becomes larger, and the image becomes larger.

a.The direction of light travel is bound to change.

Vertical irradiation is the method unchanged)

The difference in air pressure between the inside and outside of the suction cup is δp, and the resulting pressure is equal to the gravitational force of the flat glass.

The area of the round suction cup is s= r2.

p=mg/s=(。

Analysis 1Standard atmospheric pressure.

100kpa

For the analysis of the force of the glass, except for the part of the disc sucked, the atmospheric pressure of the other parts are balanced, only the disc part of the glass is considered, there is gravity downward, the size is, atmospheric pressure, upward, the air pressure in the suction cup, downward, the elastic force of the suction cup deformation, downward, to ensure that the glass is sucked, the elastic force must be greater than 0. Otherwise, it's dropped. If the air pressure in the suction cup is x, then there is an equation:

s (suction cup area) x + g (glass gravity) + f (suction cup elastic force) = s p (standard atmospheric pressure), known amount is brought in, and f must be greater than 0, x<96000 can be obtained. That is, the maximum air pressure can only be 96kpa.

2.That is to say, if the temperature is too high, the valve will fly up, calculate the critical pressure when the top fly, and then find the corresponding temperature.

At the moment of top flying, force analysis, the gravity of the valve + atmospheric pressure = the pressure of the internal gas, (only consider the area of the exhaust hole, the atmospheric pressure of the other areas are balanced) Let the internal gas pressure be x, and the equation:

m (mass of the valve) g + p (standard atmospheric pressure) s (vent area) = x s

Bring in a known amount. There is x=199079pa, and the corresponding temperature is 120°C