Physics examination questions
1 4.2010 may1day, Shanghai world Expo opens. As shown in the figure, the tickets for the Shanghai World Expo contain the chip "Expo Core" with independent intellectual property rights of China, which records the information of visitors and can exchange information with sensors all over the Expo site by wireless. When exchanging information, a lot of physical knowledge is applied, and the following knowledge is applied.
A. Echo B. Thermal effect of current
C. Electromagnetic induction D. Reflection of light
15. In the following cases, the principle of safe electricity use is
16. "Humai" is a superb singing form of Mongolian people. The singer uses skills to make the breath violently impact the vocal cords and form a bass. On this basis, he adjusted his mouth to form a treble, realizing the rare phenomenon that a person sings a treble and a bass at the same time. The following statement is correct.
A. The treble and bass in Humai refer to the loudness of the sound. The sound in Humai is produced by vibration.
C. Humaili's treble is ultrasonic and bass is infrasound. The propagation speed of treble and bass in d. Humai is different in the air.
17. Many idioms we have learned contain physical knowledge. Which of the following idioms is a "shadow" formed by light reflection?
A. a glass of bow and snake shadow B. inseparable C. alone D. immediate effect
18. As shown in the figure, there are four ways to lift the same object with simple machinery at a uniform speed (excluding mechanical self-weight and friction), among which the minimum power required is
19. The following analysis of the process of raindrops falling at a constant speed in the air (regardless of the change of raindrop quality and the buoyancy of raindrops) is correct.
A. raindrops are subjected to a balancing force. B. the mechanical energy will not change during the raindrop falling.
C. the gravity of raindrops is greater than the resistance. D. the gravitational potential energy of raindrops is converted into kinetic energy.
20. The picture shows a popular environmentally-friendly mosquito repellent-electric liquid mosquito repellent. After the mosquito repellent is electrified, its internal heating component heats the mosquito repellent. After a while, you can see "white gas" floating from above, and the room is filled with the fragrance of mosquito repellent, which plays the role of mosquito repellent. The following statement is correct.
A "white gas" is produced by evaporating mosquito repellent and then liquefying it.
"White gas" is produced by liquefaction and evaporation of mosquito repellent.
C. When the mosquito-repellent incense device works, the internal energy is converted into electric energy.
D. the smell in the room shows that there is interaction between molecules.
2 1. The high-end cars in the past have now entered people's families. The following statement about cars is correct.
A. Wearing a seat belt when driving can reduce inertia.
B when the car accelerates on a level road, the force that makes the car move forward is exerted by the road.
C. When the car is running, the air velocity above the car body is greater than the air velocity below, so the downward pressure of air on the car is greater than the upward pressure.
D. People push the station on the horizontal road, but don't push it, because the thrust of people to the car is less than the friction of the road to the car.
22. The picture on the right is a schematic diagram of a new type of energy-saving emergency desk lamp. After the desk lamp is charged, the brightness of the bulb can be changed by adjusting the resistance value R of the sliding rheostat connected to the circuit. Assuming that the power supply voltage and bulb resistance are unchanged, the image of the voltage u at both ends of the bulb changing with R is as follows
23. In physics, the increase in the speed of an object per unit time is defined as acceleration. According to this definition, if the speed of an object increases from V 1 to V2 in t time, the acceleration is. The existing ball accelerates 2s at an acceleration of 3m/s2 from standstill, and the speed of the ball at the end of 2s is
2m/s, 3m/s, 6m/s.
Two. Fill in the blanks by drawing lots (65438+24 to 27 are 0 points, 28 and 29 are 3 points, and ***22 points).
24. The picture on the right shows the escalator of a shopping mall. The figure shows some geometric dimensions of the escalator. Xiaohua, weighing 50kg, is standing on the escalator from the first floor to the second floor of the shopping mall. It is known that the escalator runs upward at a constant speed of 1m/s ... then the work done by the escalator to him _ _ _ _ _ _ _ _ _ J, and the work done to him is _ _ _ _ _ w. If the number of people standing on the escalator increases, the efficiency of the escalator is _ _ _ _ (fill in "bigger" and "smaller" If Xiao Huawei went upstairs faster,
25. The picture on the right shows the road drilling rig commonly used in road maintenance (commonly known as "woodpecker"). This machine uses compressed gas to push the piston and push the drill bit into the road. When the gas pushes the piston, _ _ _ _ _ _ _ energy is converted into _ _ _ _ _ _ _ energy; The drill bit is conical and used for _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ If its mechanical efficiency is 40%, the useful work done by complete combustion of 50 kg diesel oil _ _ _ _ _ _ j (the calorific value of diesel oil is 4.3× 107 j/kg).
26. When the maintenance workers check the circuit board with dense lines, they often observe it through a larger lens, which should be _ _ _ _ _ _ (fill in "convex" or "concave"), and the workers see an enlarged _ _ _ _ _ _ _ _ (fill in "real" or "imaginary"). Lighting is also used for maintenance, that is, to illuminate _ _ _ _ _ (fill in "lens" or "circuit board").
27. In the circuit shown in Figure A, the supply voltage is constant. When the switch S is closed, the slider P moves to a certain position, the voltage is 6V, and the positions of the two ammeter pointers are as shown in Figure B, then the resistance of R 1 is _ _ _ _ _ _ _ _ ω, and the electric power of R2 is _ _ _ _ _ _ _ _ _ _ w； at this time; If you move the slider P to the right, the indication of A 1 is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (fill in "bigger", "smaller" or "unchanged").
28. As shown in the picture, the diver's eyes are at underwater point A, there is a small fish at underwater point B, and there is a bird at underwater point C. Please make a light path diagram for the diver to observe the fish and birds.
29. As shown in the figure, two metal bars AB suspended by rubber bands are in a magnetic field, and both ends of the metal bars are connected by wires (the force of the wires on the metal bars can be ignored). When the current flows from A to B in the rod, the metal rod is static and the rubber band is just in a relaxed state. Now let the current flow from B to A, and the metal bar is still at rest. Please draw the stress diagram of the metal bar at this time.
Three. Experiment and inquiry (30 ~ 3 1 question 5 points, 32 questions 7 points, *** 17 points)
30. Xin Er has 10 identical L coins. In order to measure the density of a coin, she designed a small experiment. The experimental equipment includes an empty metal tube, a measuring cup and water. The main experimental steps are as follows:
A. Put all 10 coins into the water, and the scale at the water level in the measuring cup is as shown in the above figure;
B, put 10 coins into a metal cylinder, let the metal cylinder float in a measuring cup, and record that the scale value of the water surface at this time is 53mL；;
C, put the empty metal cylinder into a measuring cup filled with a proper amount of water, let it float, and write down that the scale value of the water surface at this time is 22 ml. ..
(1) The reasonable experimental sequence is _ _ _ _ _ _ _ (only fill in the alphabetical number)
(2) According to the experiment, the density of coins ρ = _ _ _ _ _ _ kg/m3;
(3) In the experiment, which of the following experimental methods did Xin Er use? _ _ _ _ _ _ (fill in the letter number).
A. control variable method B. transformation method C. analogy method D. accumulation method
3 1. As shown in the figure, it is the physical connection diagram of "2.5V 1W" filament resistance of small light bulb researched by Xiao Wei:
(1) There is an error in the wiring diagram. Only need to change a wire, you can connect the circuit correctly. Please put an "×" on the wire to be replaced, and draw the correct connection with a stroke line instead of the wire.
(2) After the circuit is connected, the current indicator in a certain measurement is 0.30A. In order to measure the filament resistance at rated voltage, the slider P of the sliding rheostat should be moved to the _ _ _ _ _ _ _ _ end (fill in "left" or "right").
(3) Xiao Wei measures the resistance of the filament at three different voltages, and then calculates their average values as the resistance of the filament. Do you think this is correct? And explain why.
A: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
Xiao Ming knows that when measuring the length of an object with a scale, there are some factors that will cause measurement errors, and the temperature change of the scale is also one of the reasons. He wants to study the change of scale length with temperature through experiments.
(1) Xiao Ming found two identical steel rulers with a length of 20cm, one was fully frozen in the refrigerator, the other was exposed to the sun for a long time, and then measured each other with two steel rulers. It is found that these two steel rulers are almost the same length. Please write down the reasons for the make-up exam results (only one): _ _ _ _ _ _ _ _ _ _.
(2) He redesigned the device as shown in the figure to study the change of the length of an object with temperature. In the device, AB is a copper bar with uniform thickness, and COD is a pointer that can rotate around the O point. In the experiment, the A end is fixed, and the C end of the pointer is close to the B end of the copper bar. When AB is heated by alcohol lamp, Xiao Mingcan analyzes the length change of metal rod when it is heated by observing _ _ _ _ _ _ _ _ _ _ _ _ _. The pointer in the device is designed so that the CO segment is shorter than the OD segment, which plays a role in the experiment.
(3) Please put forward a question worth exploring according to Xiaoming's experiment.
Question: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Four. Application and innovation (7 points for 33 questions, 9 points for 34 questions, *** 16 points)
33. When salvaging sunken ships at the bottom of the sea, underwater robots are often used to dive underwater to salvage the articles on board. Known ρ seawater =1.03x103kg/m3.
(1) What is the pressure of 70m seawater on the robot?
(2) At a certain moment, the robot is holding an object with a volume of 0.02m3 and a density of 2.7× 103kg/m3 underwater, and there is a vertical upward force. Find the magnitude of this force.
(3) If the relationship between seawater resistance and speed is as shown in the figure when the robot moves underwater, find the power of horizontal propulsion of the robot when the robot moves horizontally at a uniform speed of 0.5m/s underwater.
34. Electric pressure cooker combines the advantages of pressure cooker and rice cooker, which is safe and energy-saving. The rated voltage of a certain type of electric pressure cooker is 220V, and the working schematic diagram is shown on the right. R 1 and R2 are the main heater and pressure maintaining heater respectively, and the rated power of R 1 is 800 W；; L is a color-changing light-emitting diode, which is used to indicate the working state of the electric pressure cooker. When the current passing through it is less than 40 mA, it will emit red light, and when it reaches 40mA, it will start to emit green light. As long as there is a current through L, the voltage at both ends will be constant at 2V; R0 is a special resistance, and its resistance varies with the temperature in the pot; When the circuit is connected, the switch S automatically closes and the contacts A and B start to heat. When the water temperature in the pot reaches 105℃, the switch S automatically turns off the contacts A and B, turns on the contact C, and starts to maintain pressure. At this time, the water temperature in the pot is constant and does not boil.
When the electric pressure cooker (1) works normally, if the indicator light L is green, find the maximum resistance of R0.
(2) In the pressure maintaining state, the heater works normally 1h, and the power consumption is 0.2kWh. Find the resistance of R2.
(3) Using this pressure cooker to heat 5 L water at 20℃, how many degrees Celsius will the water temperature rise after working normally for 35min? It is known that 90% of the consumed electric energy is effectively utilized, and the specific heat capacity of water is 4.2× 103 J/(kg? ℃).
Huanggang 20 10 entrance examination for junior high school graduates
Science comprehensive questions, answers and scoring instructions
First, multiple choice questions
14.C 15。 C 16。 B 17。 A 18。 D 19。 A 20. A 2 1。 B 22。 C 23。 D
Two. Fill in the blanks by drawing lots (0 for 65438+24-27, 3 for 28 and 29, and 22 for * * *).
24. 1500 300 is 2.5 times larger.
25. Internal gas (filling "inside" or piston movement (filling "power" or "machinery") can increase the pressure of the drill bit on the road surface (filling "pressurization") by 8.6× 106.
26. Convex virtual less than 1 times the focal length of the circuit board
27.20 is smaller than 7.2, and there is no change.
28. The optical path is as shown in the figure (draw 1 point for CO, OA and BA, and point O must be on the left side of CA connection, and the light propagation direction must be correct).
29. The force is shown in the figure (use 1 to draw gravity g and magnetic force f, elastic force of rubber band F 1 min, F2*** 1 min; Draw two elastic forces on the gravity action line or only draw 1 elastic force on the gravity action line to get 1 point; The magnetic direction may be downward).
Three. Experiment and inquiry (30 ~ 3 1 question 5 points, 32 questions 7 points, *** 17 points)
30.( 1)CBA； (2 points) (2)7.75× 103( 1 minute) (3)BD(2 points, right 1 minute, no points will be deducted for wrong).
3 1.( 1) as shown in the figure (marking error 1, drawing correct connection 1, * * * 2);
(2) Right (1);
(3) No, the filament resistance is different under different conditions. (Conclusion: 1, reason: 1, ***2, with similar meaning, which can be scored. )
32.( 1) The length change of two steel rulers is too small, and a simple measuring tool cannot measure the slight change. (2 points, other reasonable answers can also be scored)
(2) pointer indication change (2 points, depending on the pointer deflection angle); Zoom in (2 points)
(3) When the temperature of the object changes, whether the change of the length of the object is related to the material (the length of the object itself, the change of temperature, etc.). )? (1, other reasonable answers can also be scored)
Four. Application and innovation (7 points for 33 questions, 9 points for 34 questions, *** 16 points)
33.(* * * 7 points)
(1) is obtained from the liquid pressure formula p = p = P=ρgh,
P=ρ seawater GH =1.03x103kg/m3×10n/kg× 70m (1min).
P=7.2x× 105Pa (1 point)
(2) When an object is subjected to a balanced force under water, G = F float +F lift (1 min).
(3) According to the image, the seawater resistance is directly proportional to the moving speed of the robot. When the moving speed of the robot is 0.5m/s, f= 175N (1 min).
When the machine advances at a uniform speed, the horizontal propulsion of the robot is F=f (1 min).
P = Fv =175n× 0.5m/s = 87.5w (1min).
34.(* * * 9 points)
(1) To make the indicator light emit green light, the minimum current I in the circuit is 40mA (1 min).
When the water temperature in the pot reaches 105℃, the pressure cooker is in the state of maintaining pressure and the temperature remains unchanged, so the water temperature rises to 105℃ after absorbing heat. ( 1)
(Give other reasonable solutions for reference).