Urgently ask for 150 physics calculation questions in the second year of junior high school, with an

Lens 1: Observation and Reflection.

Observe the diagram below, where is a convex lens, which is characterized by being a concave lens, which is characterized by

2. Do it yourself.

The distance between the spot and the convex lens is measured.

Experiment 2: Take a concave lens facing the sun, and then put a piece of paper on the other side of it and move it back and forth, imitating the above picture for the experiment.

3. Think about it.

A What is the smallest and brightest spot in Experiment 1? What is the distance measured with a ruler called? What does this experiment illustrate?

b What happened on paper in Experiment 2? What does this mean?

Synchronous exercises. 1. Lenses can be divided into two categories: those with thick middle and thin edges are called lenses, which have an effect on light; The one with a thin middle and a thick edge is called a lens, and it has an effect on light.

2. Myopic spectacle lenses are mirrors, and farsighted spectacle lenses are spectacles.

3. The convex lens can make the light parallel to the main optical axis at a point, this point is called the focal point, and the distance from the focal point to the optical center is called the focal length of different lenses can be different, and the same lens has a focal point.

5. The mirror that has a converging effect on light is:

a Flat mirror b. Concave lens c. Convex mirror d. Convex.

6. The mirrors that have a divergent effect on light are:

a Flat mirror b. Convex lens c. Convex mirror d. Concave mirrors.

7. Place a light-emitting bulb on the focal point of the convex lens, and after the light emitted by it passes through the convex lens, it will: (

A becomes divergent ray B. Converge on the focus.

c becomes a parallel ray d. The direction does not change.

8. The optical path diagram in the figure is wrong: (

9. Make the refracted rays in the figure.

Reading outside of class. Ice lenses in the history of our country.

As early as the Western Han Dynasty (206 BC 25 AD) "Huainan Wanbi Shu" there is a record about the ice lens: "Cutting the ice to make the circle, lifting to the sun, and taking the shadow of Ai, the fire is born." Subsequently, there was a similar record in Zhang Hua's "Naturalist Chronicles" of the Jin Dynasty.

Ice melts when exposed to sunlight, and it is doubtful that the ice lens can indeed concentrate light on the sun and set the moxa on fire. Qing Dynasty scientist Zheng Fuguang (1780 ?) According to the records of "Huainan Wanbi Technique", I did some experiments with my own hands, and confirmed that the ice lens can indeed make fire.

He wrote in "Mirror Mirror Idiot": A tin pot with a slightly concave bottom, filled with boiling water, and rotated on the ice surface with the pot, can make a smooth ice lens, and use it to gather sunlight and make paper ignite.

After the snow is clear, the students go to the field to have a snowball fight, and some dead branches and leaves in the snow are turned out, and they inadvertently catch a wild wild dog while playing, they want to roast it with fire to taste the game, but there is no fire, can you help them think of a way?

5. Calculation questions.

1 The school building has five floors, and the pressure of the water at the tap on the ground floor is measured to be 5 105 pa, so it is 10 m higher than it.

What is the pressure of water at the faucet in the building? （g=10n/kg）

2 Wang Yang's study group simulated the Magdeburg hemisphere experiment, using a copper ball with a diameter of 30cm and setting all the air in the ball.

If the atmospheric pressure at that time is extraction, what is the atmospheric pressure on the copper ball?

1 point) (points).

23. When a piece of metal is weighed in air, when it is immersed in water, the spring scale reads as, find the buoyancy, volume and density of the metal block?

24. A 200m long train passes through a mountain tunnel at a constant speed of v 36km h, and the length of this tunnel is found.

S=VT 10M, S 90S, 900M, S1 S, Car 900M, 200M=700M

25.In order to protect the environment and control soil erosion, a school environmental protection team measured the sediment content of the Yangtze River water (that is, the mass of sediment in each cubic meter of river water), they collected 100 milliliters of water samples, and measured the mass as, known the density of sediment, what is the sediment content in the river water?

The quality of each cubic meter of river water is: let the sediment content of river water be m. Then: v river water v sand v water.

Solution: m 30kg

24. When a hole appears in the reservoir embankment under the water surface, water gushes out of the hole to form a "pipe surge". "Pipe surges" can damage the levee or even cause it to burst. For example, if there is a "pipe surge" with a cross-sectional area of 800cm2 in the underwater part of a certain embankment, find: (g takes 10n kg).

1) The pressure generated by the water at that point. (2) The berm personnel use sand bags on the outside of the embankment to "plug the leakage", and the impact force of the water on the sand bags.

25. People often use the phrase "the tip of the iceberg" to describe things, revealing only a small part of them, and more of them are hidden under the surface phenomenon. In fact, it is true that only a "corner" of an iceberg is exposed in the seawater, so how much of the exposed "corner" is the size of the iceberg? Please use your knowledge of physics to be explained by calculations and brief texts.

It is known that p ice 103kg m3, p seawater kg m3).

26. When a certain type of hydraulic truck crane weighs 8t, the contact area between the car and the ground is about 4000cm2, when it lifts 2t goods and is stationary in the air, as shown in Figure 25, L1 2m, L2 6m, not counting the weight of the crane arm, how big should FL be? What is the pressure on the ground? (g takes 10 n kg).

This benevolent brother is really ruthless, he wants sixty things at once, and he also needs the process and the answer...

3. This question consists of 5 questions, with a total of 40 points. The solution should include the necessary textual descriptions, equations, and important calculation steps. Those who only write the final answer will not be scored.

For questions with numerical calculations, the numerical values and units must be clearly written in the answers. 13.(8 points) Skydivers land safely by parachute.

It is assumed that the drag experienced when the parachute is fully opened is proportional to the square of the velocity (scale coefficient k=20ns2 m2).If the total mass of a skydiver and the parachute is 72kg, if he opens the parachute from a very high place and lands at a speed equal to the speed at which he lands without a parachute falling freely from a height h, try to find h. (If the air resistance is not counted when the parachute is not used) 14

8 points) As shown in Figure 12A, a block with a mass of m=1kg is stationary at point A on a rough horizontal plane Starting from the moment t=0, the block moves to the right under the action of the horizontal force f that changes according to the law as shown in Figure B, and the velocity of the block at the end of the 3s is exactly 0 when it moves to point B, and the block at the end of the 5s just returns to point A The dynamic friction factor between the block and the rough horizontal plane is known =, find: (1) the distance between AB; (2) The work done by the horizontal force f on the block within 5s Fig. 1215 (8 points) As shown in Fig. 13, at a height of 45 m from the ground, there is a small ball A that is thrown horizontally at the initial velocity v0 10 m s, at the same time, there is a block B directly below a that also slides out in the same direction with the same initial velocity, the dynamic friction factor between B and the ground is can be regarded as a mass point, the air resistance is not counted, and the gravitational acceleration is taken g 10 m s2, find: the landing time of a ball and the horizontal distance thrown by it; When the ball A lands, how far apart are A and B Fig. 1316 (8 minutes) On an inclined plane with an inclination angle of , a slider with a sail slides down the inclined plane from a stationary start, the mass of the slider (together with the sail) is m, the dynamic friction factor between the slider and the inclined plane is , and the backward air resistance of the sail is proportional to the speed at which the slider slides, i.e., f kv.

Figure 14 shows the image of V t of the slider sliding down the inclined plane from a stationary start, and the inclined line in the figure is the tangent of the velocity graph line at time t 0. The maximum acceleration and maximum velocity of the slider slider are obtained from the image; If m 2 kg, 37°, g 10 m s2, find the value of and k Fig. 14 Fig. 1517 (8 points) As shown in Fig. 15, a thin plank of mass = and a metal block b of mass = are stacked on top of a smooth tabletop, and the length of a is l= b and there is a light wire around the fixed pulley connected to the block c of mass =. The sliding friction factor between b and a, the maximum static friction can be regarded as equal to the sliding friction.

Ignore the mass of the pulley and the friction between the wheel and the shaft. At the beginning, all objects are at rest, the rope is straightened, B is located at the left end of A (as shown in the figure), and then let go, find how long it takes T for B to break away from the right end of A (let the right end of A be far enough away from the pulley) (take G=10M S2).

The second-hand house is Feng Shaofeng's.

16. How long does it take for a train to cross a railway bridge with a length of 1800m at a speed of 20m s and pass through the 1800m long railway bridge? 17. The car should be tested before leaving the factory. In one test, the car was driven at a speed of 8 ms for 500 seconds on a simulated mountain road, and then 100 seconds at a speed of 20 ms on a simulated mountain road.

Find: (1) the distance traveled by the car on the simulated road; (2) The average speed of the car over the course of this test. 36 A student measured his pulse beating 80 times per minute when walking, and he passed a distance of 2 meters on average every 3 steps, and he measured that he had walked exactly 45 steps and his pulse beat 40 times

1) How long is this journey? (2) What is the average speed at which he walks? 18. As shown in the figure, the car travels at a constant speed from a certain place to Nanning When it arrives at place A, the clock in the car is displayed as 10:15; When it reaches place B, the clock shows 10:45 a.m

1) How many hours does it take for a car to get from A to B? (2) The speed of the car from A to B; (3) If the car continues to drive at a constant speed at this speed, how long does it take to reach Nanning from place B 17. A column of troops with a captain of 360m passes through a long bridge at a uniform speed, and the time it takes for the army to pass the bridge is measured to be 9min, and the speed of the army is obtained: (1) the speed at which the army advances; (2) The time when all this army walked on the bridge.

18. Xiao Ming's family took a taxi, and when they took the car to the destination, the driver showed the fare invoice as shown in the following table, asking: (1) The speed of the taxi? (2) What is the average speed of a taxi?

Vehicle number date on the bus and off the unit price (yuan km) mileage amount (yuan) e·v-882006-1-110:0010:052 006 19, riding a bicycle uphill with 50s, downhill with 20s, slope length 100m, find the average speed uphill, the average speed of downhill, the average speed of uphill and downhill.

At 8:30 a.m. on December 26, a magnitude 8 9 large ** occurred in the sea near Indonesia, causing a strong tsunami. **At the time of the incident, a group of children were playing on the beach in the Maldives, 1,500 kilometers from the epicenter. If they were alerted in time and immediately ran to the high ground 3,000 meters from the coast, they would not have been swept away by the waves.

If so, at what time will they be alerted at the latest before they can escape death? (Tsunamis travel up to 500 km-h-h in the ocean, and children flee to highlands at speeds of up to 100-metre-minutes).

50, your teacher is crazy!

Calculation questions (6 points per question, 12 points in total).

33.The length of the focal length f of the lens indicates the size of the refractive ability, the shorter the focal length, the stronger the refractive ability, usually the reciprocal of the lens concentration is called the power of the lens, which is expressed by , that is, =1 fUsually, the power of our glasses is the power of the lens multiplied by 100.

1) What is the focal length of the lens with a sum of focal lengths?

2) What is the power of spectacle lenses at +300 degrees and -400 degrees? What is the focal length?

34.The car is driving along a straight highway at a speed of 20m s, there is a mountain cliff in front of it, when the car passes somewhere, the driver honks the horn, and hears the echo after 2s, how far is it from the cliff when the horn is pressed? (V sound = 340 m s).

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