Ask for 30 physics application questions in the eighth grade

1: The angle between the escalator and the ground of a certain subway is 45 degrees, and it moves at a speed of 1m s in size, if the subway station is 70m deep under the ground, how much time does it take for passengers to take the escalator from the subway station to the ground? What is the displacement of the passenger at this time?

2: A column of long L marches at a speed of V, and the communicator rushes from the end of the line to the head of the line with velocity U, and immediately returns to the end of the line with velocity U to find the distance the team has advanced during this time

3: A road repairer in the tunnel of long s=100m, suddenly found that a train appeared at 200m away from the right tunnel mouth, the position of the road repairer happened to be in the position that can safely get out of danger whether left or right, ask what is the distance between this position and the right exit of the tunnel? How many times the minimum speed at which he can run should be at least the speed of the train?

4: Raindrops fall freely from the eaves, and someone uses a stopwatch to measure the time it takes for the raindrops to pass through a high window, and find the height from the top of the window to the eaves

5. There are mkg of aqueous solutions with densities of P1 and P2 respectively (it is known that P1 is greater than P2), and only these two solutions can be used to prepare a density of .

How many kilograms of solution is P-mix = 1 2 (P1 + P2)?

6 Xiao Ming's family bought back an electric kettle, its internal circuit can be simplified as shown in the figure, this kettle is heated by an electric heating pipe, the rated voltage of the electric heating pipe is 220V, and the rated power is 1kwWhen the water in the kettle is boiling, the temperature control switch S is automatically disconnected, and the electric kettle is in a state of heat preservation. (The resistance values of r1 and r0 are unchanged).

1) If the water in the pot is boiled at a standard atmospheric pressure, how much electricity will be consumed? How long does it take to boil this pot of water normally? [c water = .)

2) When the electric kettle is in the insulated state, it saves electricity compared to the normal heating, why?

3) If the electric kettle is in the insulated state, the actual power of the electric heating pipe R1 is rated.

Power 1 16, what is the resistance of r0 in the figure?

It's really hard to find, so I recommend buying this exercise book.

1: The angle between an iron escalator and the surface is 45 degrees and 1m s speed shift.

At a depth of 70 meters, passengers need a small number of trains to train at a depth of 70 meters.

Standing on the escalator to reach the surface? Less passenger movement?

2: Column l team marching speed v correspondent team tail speed u rush row.

Immediately speed u back to the tail of the line. Find the distance traveled by the team between segments.

There is a mountain gorge that is 1,200 meters wide and is lined with cliffs on both sides. Someone fired a shot in the gorge, and he heard the first two echoes five seconds apart, asking for the distance between the two cliffs. (The speed of sound in the air is 340m s).

If the distance of a person from one cliff is x, and the distance from another cliff is 1200-x, the sound to the two cliffs and back time: 2x 340, 2 (1200-x) 340

From the inscription, 2x 340-2(1200-x) 340=5 is solved x=1025, 1200-x=175

Therefore, the distance between man and the two cliffs is 1025 meters and 175 meters respectively.

Child, there are many versions of physics textbooks in our country

(1) It is not a uniform linear motion.

Because you walk 10km in the middle of each milestone, but the time it takes is different, you can just do the math yourself.

2) The time after 30km is from 6:45 to 7:39, and 54 minutes is the hour.

30 divided by kilometers per hour.

Whether the car is moving in a straight line at a uniform speed. No. Be.

What is the average speed after 30km.

The time is 7:39-6:45=44 minutes.

v=s t=30 44 units are kilometers of minutes.

You can change it to kilometers yourself.

Something.

A and B are 6000m apart, a car travels at a speed of 30m s in the first half of the distance, and the speed of the car is 20m s in the second half of the distance, and the average speed of the car in the whole journey is found.

A train runs evenly at a speed of 30m s, the driver suddenly finds that there is an emergency ahead, starts braking after 06s, and then slides for 52m, and the car stops, then the average speed from the occurrence to the stop is.

The great poet Li Bai of the Tang Dynasty was based on the essayist Li Daoyuan of the Northern Wei Dynasty"The white emperor of the court, twilight to Jianglin"The sentence is written as a pre-ancient sentence:"Between the white emperor and the clouds, the thousands of miles of rivers will be returned one day"Please estimate the average speed of the boat.

In a valley made up of two parallel cliffs, the hunter fired a shot into the air, and two echoes were heard after the reticulance, and if the speed of sound was 340 m s at that time, the width between the canyons would be.

A and B two bicycles, in a straight highway in the same direction of a constant speed, car A in 5 minutes to travel 1800m, car B in the car on the way through a road sign 2 minutes earlier, ask car A to catch up with car B when how far away from the road mark.

I can't find that many

1、t1=s1/v1=96cm/(

S2 = V2 * T1 = 5m S*120s = 600m > 500m energy. 2. Collapse t2=s2 v2=500m (5m s)=100st1=s1 v1=96cm (>100s can serve and merge. 3. T2=S2 V2=500m (5M S)=100Sv1=S1 Tuantan Brother T2=96cm 100S=> that is, as long as the combustion speed of the ignition wire is less than or equal to it, it can run to a safe area 500m away.