Physics midterm papers and answers in the second volume of the second day of junior high school

First, multiple-choice questions (1-9 questions, 2 points for each question; 1 1- 12 multiple questions, 3 points for each question)

1 In the following process, one force acts differently from the other three, and it is ().

Knead plasticine into different shapes. B, the train stops slowly due to resistance.

C, the apple falls vertically by gravity, and d, the shot put is forcibly pushed out.

In the four examples shown in the figure, the purpose is to reduce friction.

An ordinary middle school student stands on a level ground with his feet, and his pressure on the ground is close to ().

a、50 N、 103Pa B、50 N、 104Pa C、500 N、 103Pa D、500 N、 104Pa

Through inquiry learning, Xiaoli thought about a question: When she swings to the highest point on the right, what kind of motion state will she be in if all the forces she receives disappear? She made the following guess, do you think it's accurate (black dots in the picture indicate Xiaoli) (),

The picture shows some scenes that Zhang San saw on the playground. He used physical knowledge for analysis, and the following analysis is correct ()

A, the football kicked by Wang Hao slowly stopped when rolling on the grass, because the football was not stressed.

B, Zhang Hong didn't stop immediately after crossing the 100 meter line, because all objects were subjected to inertia.

Li Ning jumps very high. When he jumped to the highest point, he was in balance because the speed was 0.

D. zhangyan is doing pull-ups. When he was still on the horizontal bar, the pull of the horizontal bar on him and his gravity were a pair of balancing forces.

The following are the sports icons of the 29th Olympic Games in 2008. In these sports, the ground pressure of athletes is the greatest ().

A, archery b, weightlifting c, fencing d, shooting

7 2065 438+0 1 Jiangnan Middle School Sports Meeting, Xiaohua threw a frisbee horizontally, and the fast-moving frisbee rose higher and higher. Viewed from the side, the shape of a frisbee during flight should be () in the following figure.

A, B, C, D,

8 As shown in the figure below, let the pressure of water on the bottom of the bottle be P, and the pressure of the bottle on the desktop be P. If the bottle is upside down (as shown in Figure A) instead of upside down (as shown in Figure B), then the change of P and P is ().

A, P gets smaller, P gets bigger, B, P gets smaller, P gets smaller, C, P gets bigger, P gets smaller, D, P gets bigger, P gets bigger.

As shown in the above figure, two cylindrical containers A and B with the same volume are filled with water. If placed as shown in the figure, the bottoms of the two containers A and B will be subjected to the pressure sum of water and the pressure sum: ()

A, B, C, D,

The following statement is incorrect.

A, centrifugal pump uses atmospheric pressure to pump water up.

B. Divers should wear pressure diving suits when diving into deep water.

C, make the schoolbag belt wider, which is more comfortable to carry, because it relieves the pressure on the shoulders.

D, where the gas velocity is high, the gas pressure is low, and people close to the tracks will be attracted to the train when the train passes.

1 1 About some physical concepts and laws, the following statement is incorrect ().

A, when the object A exerts a force on the object B, the object A must also be subjected to the force.

B. If the three elements of two forces are the same, the two forces must be balanced forces.

C, the motion state of the object will inevitably change after the force is applied.

D, the egg hit the edge of the bowl, and the egg was broken, because the force on the egg was greater than that on the bowl.

Second, fill in the blanks (2 points; 3 points; 3 points; 4 points; 4 points)

12 in foggy weather, the driver of the fast-moving B car braked immediately after seeing the A car not far away, and still hit the A car, causing a rear-end collision (as shown in Figure 8). You can see this power by observing the rear of a car.

13 There is a square stop on the horizontal table in the moving train compartment. When the train moves in a straight line at a uniform speed, the pulley is subjected to _ _ _ _ _ force (regardless of air resistance). When the train suddenly stops, the wood block will slide to _ _ _ _ _, and the friction force on the wood block is in the direction of _ _ _ _. (Before and after filling in)

14 There is an object that weighs 500N and is still on a horizontal table. At present, it is pushed horizontally to the right with a force of 20N, but it is not. At this time, the friction it receives is pushed to the right with a force level of 40N, making it move in a straight line at a uniform speed. At this time, the friction it receives is pushed to the right with a force level of 45 N.

15 as shown in fig. 9, put a thin-walled container with a weight of 2N and a bottom area of 20cm2 in the middle of a horizontal desktop with an area of 50 cm2, and fill the container with water with a height of 10cm and a weight of 3N, then the pressure of water on the bottom of the container is _ _ _ _ _ _ _ _ pa, and the pressure of the container on the horizontal desktop is _ _ _. (water =1.0103kg/m3, g = 10N/ kg)

16 As shown in the above figure, two containers A and B with the same bottom area and mass are respectively filled with different liquids with the same mass and placed on a horizontal desktop, so the pressure of the liquid at the bottom of the container is PA PB, and the pressure of the container on the desktop is PA PB. (optional greater than or less than)

Three, drawing questions (2 points; 2 points)

17( 1) The ball is rolling down the slope with acceleration. Draw a schematic diagram of gravity on the ball and pressure on the inclined plane.

(2) Draw a schematic diagram of gravity and friction when object A slides upward at a uniform speed on the inclined plane.

Four, experimental questions (6 points; 8 points; 6 points)

18 when the physics study group explored the relationship between gravity and mass of objects, the experimental records were as follows:

The mass m/kg of the measured object, the gravity G/N ratio (g/m)/NKG- 1

Average value of G/m/nkg- 1 ratio.

Object 10. 10.999.9

Object 20.2 1.969.8

Object 30.32.9 19.7

(1) Measuring tool _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _;

(2) Fill in the average value of the ratio G/m in the blank of the above table;

(3) Analyzing the experimental data in the table, the conclusion is: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (2 points)

(4) In space, the above experiments will be completed.

19 in the activity of exploring which factors are related to the magnitude of sliding friction,

(1) On the horizontal long board, use the spring dynamometer to pull the block A horizontally to the left to make it move in a straight line at a uniform speed. The indicator of the spring dynamometer is shown in Figure A. According to the knowledge, the sliding friction of the wood block is n.

(2) After Xiaohua cut off half of the wood block vertically, the sliding friction on the wood block was measured to be half of the original. She concluded that sliding friction decreases with the decrease of contact area. What do you think is the question in her inquiry? How to confirm whether the sliding friction is related to the contact area only by using the existing equipment? Briefly explain your practice. (2 points for each space)

(3) During the communication after the experiment, Xiaohua found that some students changed the experiment into the experimental device as shown in Figure B: one end of the spring dynamometer is fixed, the other end is hooked on Block A, and there is a long wooden board below, which is pulled to the left along the horizontal ground during the experiment. The advantages of the improved device are that (only one is written; 2 points).

20 Xiaoming measured the atmospheric pressure with 4.5mL syringe, spring dynamometer, balance and other equipment. The experimental steps are as follows:

(1) Push the piston of the syringe to the bottom of the syringe barrel, and then block the small hole of the syringe with a rubber cap. The purpose of this is _ _ _ _ _ _ _.

(2) As shown in the figure, tie the syringe piston with a string so that the other end of the string is connected with the hook of the spring dynamometer, and then slowly pull the syringe cylinder horizontally to the right. When the piston in the syringe is at rest, write down that the indicator of the spring dynamometer is 8.2N.

(3) The length of all scales of the syringe is 6cm, and the cross-sectional area of the piston is cm2.

(4) The measured atmospheric pressure is _ Pa. (Keep two decimal places)

Five, calculation questions (4 points; 4 points; 8 points)

2 1 In an activity, the total mass of a school bus and its students is 9000kg, and the total contact area between the wheels and the ground is 0. 15m2. At this time, the resistance of the school bus is 0.05 times of the vehicle weight. Find the pressure and pressure of the school bus on the ground at this time (1); (2) The horizontal traction provided by the school bus engine. (g= 10N/kg)

Cuboid concrete blocks as shown in the figure are often used as pile drivers in construction sites. Find: (1) the mass and gravity of the concrete block; (2) The pressure on the ground when the concrete blocks are tiled. (The density of concrete is 2.8 103kg/m3, and g is 10N/kg).

As shown in the figure, a container with the mass of 1 kg is filled with 5 kg of water, and the bottom area of the container is 100 cm2. The container is placed on a horizontal desktop with a desktop area of 0.9 m2 and g of 10 N/kg. Find:

(1) The pressure of the container on the desktop. (2) The pressure of the container on the desktop. (3) Pressure of water on point A .. (4) Pressure of water on the bottom of container.

Answer:

Inertia 1A, 2B, 3D, 4A, 5D, 6B, 7A, 8D, 9C, 10Abd,1/bcd, 12 leads to object deformation 13, two. 15, 1 03pa2.5103pa16 is less than or equal to 17, slightly 18 spring dynamometer balance 9.8 gravity is proportional to mass, and air cannot be exhausted. 19. Put the wooden block flat and then horizontally, and measure the friction force respectively for comparison; It is possible to read out 20,0.751.09105pa21,(1) 9 104n, 6105pa (2) 4 when the spring dynamometer is at rest. 22, (1) 700kg 7000 N(2) 1.4 104 Pa, 23 (1) 60n (2) 600pa (3)104pa (4).