The examination questions and answers of the mid-term exam in the first volume of physics in the second day of junior high school

Beijing normal university eighth grade second volume physics midterm examination paper

Multiple choice questions (each small question accounts for 20% and 2 points)

1, in the picture below, which one can correctly represent the situation that light obliquely enters the water from the air ()?

2. From the perspective of physics, please choose the correct explanation of the words with dots in the following poems; ( )

"The eagle strikes the sky, the fish jumps shallowly, and all kinds of frosty days compete for freedom" (Qinyuanchun): Xiangjiang River is clear and the river surface is shallow.

At the bottom, the water and the sky set each other off, and the fish seemed to fly in the blue sky.

First, the Xiangjiang River is very shallow, which is a kind of realism. B, this is a reflection of light, and the bottom of the water is a real image.

C, this is the reflection phenomenon of light, the bottom of the water is a virtual image D, this is the refraction phenomenon of light, and the bottom of the water is a virtual image.

3, basketball can continue to fly in the air, this is because ()

Basketball is driven by players. B, basketball has inertia.

C. Basketball is influenced by inertia D. The inertia of basketball is greater than air resistance.

4. As shown in figure 1, the two forces balanced by each object are: ()

5, the following belongs to the harmful friction is ()

A. Friction between bicycle axle and bearing B. Friction between bicycle pedal and shoes

C. Friction between the brake and the wheel when the bicycle brakes D. Friction between the handlebar and the hand of the bicycle.

6. When farmers remove the sand mixed with soybeans, they often put the soybeans on an inclined desktop, and the soybeans roll down the desktop, while the sand remains on the desktop. This is mainly ()

A. the density of sand grains is higher than that of soybeans. B. The volume of sand grains is smaller than that of soybeans, and it is not easy to roll down.

C. the pressure of sand on the desktop is less than that of soybeans. D. the sliding friction of sand grains is greater than that of soybeans.

7, about the synthesis of two forces on the same line, the following statement is correct ().

A the resultant force of two nonzero forces must be nonzero.

The resultant force of the two forces must be greater than either of them.

C. to find the resultant force of two forces is to add them up.

D Regardless of the direction of the two forces, the direction of the resultant force is always the same as that of the larger force.

8. A physics book is resting on a horizontal desk, which belongs to a pair of balancing forces: ()

A. The pressure of the book on the desktop and the support of the desktop to the book B. The gravity of the book and the support of the desktop to the book

C. Gravity on the desk and the support of the desktop to the book D. Gravity on the book and the pressure of the book on the desktop

9, slide show, want to let the screen enlarge the letter "f", then the correct way to put the slide show should be ().

10, understanding of force, the following statement is wrong ()

A. When clapping, the left hand is affected by the right hand, and the right hand is also affected by the left hand;

B. Pressing the spring by hand shortens it, indicating that the force can change the shape of the object;

C. When the force acts, there is a force-applying object first, and then there is a force-bearing object;

D kick the ball hard, and the ball changes from static to moving, which shows that force can change the motion state of the object.

2. Fill in the blanks (29% 65438+ 0 for each blank)

1, a beam of light parallel to the main optical axis of the convex lens shines on the surface of the convex lens, forming a smallest and brightest spot on the optical screen 5cm away from the mirror surface, so the focal length of the convex lens is _ _ _ _ _ _ cm. If the distance between the object and the convex lens is 8cm, the object will form _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

2. The lens of the camera is equivalent to _ _ _ _ _ lens, and the film is equivalent to _ _ _ _ _ _ _. When taking pictures, the distance from the scene to the lens should be _ _ _ _ _ _ _ _.

In order to prevent forest fire, it is not allowed to throw away transparent beverage bottles anywhere in the forest. This is because rainwater has _ _ _ _ _ _ _ effect on light and _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

4, convex lens has _ _ _ _ _ effect on light, concave lens has _ _ _ _ _ effect on light. Myopia glasses belong to _ _ _ _ lenses, and reading glasses belong to _ _ _ _ _ _ lenses.

5. The human eye is like a magical camera, in which the lens is equivalent to the _ _ _ _ lens in the camera lens, and the image formed by external objects on the retina is the real image of _ _ _ _ _.

When people play football, there is a force between _ _ _ _ and _ _ _ _. If the ball is taken as the research object, the object of force application is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

7. An object is acted by two forces on the same line, F 1=30N, F2= 15N. Then the resultant force of these two forces is _ _ _ _ _ _ _ _ _ _ _.

Bicycle is a common means of transportation for students. Please fill in the corresponding question number on the horizontal line.

(1) by increasing the pressure to increase the friction force is _ _ _ _ _;

(2) by increasing the roughness of the contact surface to increase the friction force is _ _ _ _ _ _ _ _;

(3) by adding lubricating oil to reduce friction is _ _ _ _ _ _ _;

(4) it is _ _ _ _ _ _ _ that reduces friction by rolling rather than sliding;

A. the surface of the pedal is rough. B. when braking, squeeze the brakes hard.

C. let the wheels turn. Always oil the chain.

9. With a force of 20 N, press an 8 N heavy object tightly against the vertical wall and stand still. At this time, the friction force on the object is _ _ _ _ _ _ _ n.

10, the total weight of the box filled with sand is 200N, and it moves in a straight line along the ground at a uniform speed under the action of a horizontal pulling force f of 50N, and the friction between the box and the ground is n. To reduce the friction between the box and the ground, it can be _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ (filled in by an operable method).

1 1. Sometimes people want to use inertia, and sometimes they want to prevent the harm caused by inertia. Please illustrate the above two points with examples. (No need to explain)

①___________________________________________________________________________;

②___________________________________________________________________________;

III. Drawing questions (5%, 2 points for the first question, 1 point for the second question and 2 points for the third question)

1. Complete the light path Figure 2. Fill in the appropriate lens 3 in the box and draw the gravity diagram of the object with the weight of 100N on the inclined plane.

Four, the experimental questions (28% 65438+ 0 points per grid, drawing questions 2 points, the fifth question 4 points)

1. In the experiment of observing convex lens imaging, one step is to adjust the height of candle, convex lens and light screen. The candle should be lit on _ _ _ _ _ in this step (fill in "before" or "after"). If the position of the convex lens remains unchanged, put the candle flame at points A, B, C and D in turn, and adjust the position of the light screen respectively.

(1) When the candle flame is placed in _ _ _ _ _ _, the image on the screen is the largest;

(2) When the candle flame is placed in _ _ _ _ _ _, the image on the screen is the smallest;

(3) When the candle flame is placed in _ _ _ _ _ _, the screen is farthest from the convex lens when the clearest image appears on the screen;

(4) When the candle flame is placed in _ _ _ _ _ _, no matter how you move the screen, you can't get the image of the candle flame on the screen;

(5) When the candle flame is placed at the point of _ _ _ _ _ _, an enlarged image can be observed;

6. When the candle flame moves from A to B, the size of the image changes _ _ _ _ _, and the distance between the image and the convex lens changes _ _ _ _ _.

2. As shown in the figure, the maximum measured value of this spring dynamometer is _ _ _ _ n, the dividing value is _ _ _ _ n, and the indicator in the figure is _ _ _ _ _ _ n..

3. In the experiment to explore the relationship between the gravity of an object and its mass, the hook codes are hung on the spring dynamometer one by one, and the quality of the hook codes and the corresponding indexes of the spring dynamometer are read out and recorded in the table.

① In the picture on the right, the mass m is taken as the abscissa and the gravity g as the ordinate, so as to trace and connect lines;

(2) The drawn line is a _ _ _ _ _ _ _ _ _, indicating that the gravity of an object is _ _ _ _ _ _ ratio to its mass;

(3) It can be concluded from the figure that the relationship between gravity and mass is _ _ _ _ _ _ _; The ratio of gravity to mass obtained in the experiment is _ _ _ _ _ n/kg, and its physical meaning is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

4. As shown in the figure, let the same car slide down from the same height on the same slope and slide to the horizontal surface covered with different materials respectively.

(1) Let the same car pass on the same slope at the same height, with the purpose of _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _;

(2) The distances traveled by cars on different planes are not equal, which means that the larger the plane is, the more _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

③ Reasoning: If the plane is absolutely smooth and the resistance of the object is zero, then its speed will change _ _ _ _ (fill in "yes" or "no"), and the car will do _ _ _ _ _ _ _ _ _ _ _ and move forever.

As shown in the picture, there is a wooden block and an iron block on the horizontal desktop. Now it is necessary to explore who is rougher on the lower surface of wood block or iron block. Please design an experiment with a spring dynamometer to verify your guess, and write down the experimental steps and possible experimental conclusions.

① Experimental steps:

② Possible experimental conclusions:

5. Calculation questions (18% 8 points for the first question, 4 points for the second question and 6 points for the third question)

1, a skydiver weighing 65Kg, jumped off the plane. (g = 10N/Kg)

(1) What is the resultant force on the athletes before opening the umbrella? What is the direction? (excluding air resistance)

② After opening the parachute, the vertical air resistance at a certain moment is f =1000 n.. What is the magnitude and direction of the resultant force acting on the athletes at this moment?

2. The weight of a car is 1× 104N, and all the resistance when driving at a constant speed is 0.06 times its weight. How much traction does this car have?

3. Tie an object weighing 500N with a wire rope.

(1) When the wire rope pulls the object to rise at a uniform speed, what is the pulling force of the wire rope on the object?

(2) When the wire rope pulls the object to suspend in the air, what is the pulling force of the wire rope on the object?

(3) What is the resultant force on the object when the wire rope pulls it down at a constant speed of 2m/s?

Beijing normal university eighth grade second volume physics midterm examination paper

Reference answer

Multiple choice questions (each small question accounts for 20% and 2 points)

1、C 2、D 3、B 4、A 5、A 6、D 7、D 8、B 9

2. Fill in the blanks (29% 65438+ 0 for each blank)

1、5; Fall head; Enlarge; Real 2, convex; Light curtain; 3, more than 2 times of convex lens; Convergence 4, convergence; Divergence; Concave; Convex 5, convex; 6, feet; Ball; Foot; Ball 7,45n or 15N 8, ① b; ; ②A； ③D； ④ C

9. 8N 10, 50N Reduce the sand (or install rollers under the box) 1 1, and ask open questions (as long as they are reasonable).

III. Drawing questions (5%, 2 points for the first question, 1 point for the second question and 2 points for the third question)

1, each ray 1 min

2. Draw concave lens 1.

3. Scale 1, center of gravity and direction 1.

Four, the experimental questions (28% 65438+ 0 points per grid, drawing questions 2 points, the fifth question 4 points)

1, before; ① C2A3C4D5C and D6 are large; big

2、5; 0.2; 1.2

3.① Slightly ② Straight line passing through the origin; Positive ③ g = mg; ; 10; The gravity of an object with a mass of 1Kg is 10N.

4.① Ensure that the car has the same initial speed every time it moves on a horizontal plane. Small; Far 3 will not; Uniform straight line

5.① Put the wood block on the iron block, use the spring dynamometer to pull the iron block to do uniform linear motion on the horizontal desktop, and write down the indicator f1of the spring dynamometer; (2) Put the iron block on the wood block, use the spring dynamometer to pull the wood block to do uniform linear motion on the horizontal table, and write down the pointer F2 of the spring dynamometer; if f 1 >； F2, indicating that the friction of iron block is large and the lower surface of iron block is rougher; If f 1

5. Calculation questions (18% 8 points for the first question, 4 points for the second question and 6 points for the third question)

1, solution: ① G = mg (2 points)

=65Kg× 10N/Kg (1 min)

= 650 Newton (1 point)

Direction: vertically downward (1 point)

② f = f-g =1000n-650n = 350n (2 points).

Direction: vertically upward (1 point)

2. Solution: f = 0.06g = 0.06x1x104n = 600n (2 points).

F=f=600N because the traction and resistance of a car running at a constant speed are balance forces. (2 points)

3. solution: ① F = G = 500 N because the tension and gravity are balanced when the object rises at a uniform speed; (2 points)

(2) Because the object is at rest, tension and gravity are balance forces, so f = g = 500 n; (2 points)

(3) Because the object is falling at a uniform speed, the pulling force and gravity are balanced forces, so the resultant force F = 0N；; (2 points)

Volume II