Comprehensive exercises. I even brought the answer. . .

1. Fill in the blank: (65438+ 0 for each blank, ***20)

1, the force is the action of objects on _ _ _ _ _ _, and the action of forces between objects is _ _ _ _ _ _.

2. The content of Newton's first law is that all objects are always in a state of _ _ _ _ _ or _ _ _ _ _.

3. Pressure is a physical quantity representing _ _ _ _ _ _ _ _ _ _; The water pressure at 20 meters below the water surface is _ _ _ _ _ _ _ _ Pa.

4. Usually, the atmospheric pressure equal to _ _ _ _ mmHg is called standard atmospheric pressure; 1 standard atmospheric pressure is equal to _ _ _ _ _ _ _ _ Pa.

5. Buoyancy is produced by the liquid on the object going up and down, and the direction of buoyancy is always _ _ _ _ _ _ _.

6, a ball with a mass of 300 grams, when it floats on the surface of liquid, the buoyancy is _ _ _ _ _ Newton.

7. In mechanics, work includes two necessary factors, one is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

8, the car driving at a constant speed on a straight road, forward traction _ _ _ _ _ backward friction; An object whose density is less than that of water floats in the water, and the buoyancy it receives _ _ _ _ _ _ _ the gravity of the object. (optional "greater than", "equal to" or "less than")

9. Lever balance means that the lever is in a state of _ _ _ _ _ _ _ _ or _ _ _ _ _ _ _.

10, it takes 100 seconds to lift an object with a mass of 100 kg at a uniform speed with a moving pulley, so the rising speed of the free end of the rope is _ _ _ _ _ _ _ m/s, and the power of the lifted object is _ _ _ _ _ _ _ _ _ _ _.

Second, multiple-choice questions: (2 points for each question, ***50 points)

1, which of the following statements is incorrect? :( )

A, when an object is stressed, there must be other objects exerting force on it;

B, the rising hydrogen balloon is not affected by gravity;

C. When swimming, people exert force on water, and water also exerts force on people;

D. Apples hanging on trees are also affected by gravity.

2. When a classmate vertically lifts a bucket weighing 200 Newton with a force of 250 Newton, the magnitude and direction of the resultant force on the bucket are: ()

A, 450 Newton, upward; B, 450 Newton, downward; C, 50 Newton, downward; 50 newtons, up.

3, about the inertia phenomenon, the following statement is wrong: ()

A, people walk, knocked down by a stone will fall forward;

B, when the sand is sent to the carriage with a shovel, the shovel will not move, and the sand will still move forward;

C. When the car suddenly starts, passengers standing in the car will fall forward;

D, there is a very smooth paper on the desktop, with an egg on it. When the note was quickly taken away, the eggs remained on the table.

4. Which two kinds of forces are balanced forces? :( )

A, when pulling the caught fish out of the water with a fishing rod, the pulling force and the gravity of the fish;

B, traction and resistance when the car moves in a straight line at a constant speed on a straight road;

C, push the box with great force, and the box is finally pushed, the human thrust and the friction on the box;

D. The gravity of TV and telephone on the desktop and the pressure on the desktop.

5. Which of the following is to reduce friction? :( )

A uneven patterns are engraved on the soles and tires; B, sprinkle some slag or sand on the muddy road in rainy days;

C. replacing sliding friction with rolling friction; D, increase the pressure and increase the roughness between contact surfaces.

6. Which of the following statements is wrong? :( )

1. Pascal summed up the law of inertia of mechanics; B, experiments in the hemisphere of Fort Madre show that there is atmospheric pressure;

C Archimedes discovered the calculation method of buoyancy; D, atmospheric pressure value measured by Torricelli experiment.

7. A hook code 1 Newton is hung on the hook of the spring scale. When the hook code is submerged in water, the pointer of the spring scale is 0.87 Newton, and the buoyancy of water to this hook code is: ()

A, 0. 13 Newton, b, 1.87 Newton; C, 0.87 Newton; D, 1 Newton.

8. As shown in the figure, in a container filled with water, the pressure of water on points A, B and C in the container is: ()

A, water has no pressure on point a; B, water has no pressure on point C;

C, water has the greatest pressure on point A and the smallest pressure on point B; D, the pressure of water on point B is the largest, and the pressure on point A is the smallest.

9. Put the same ball in three liquids with different densities, and the ball is at rest as shown in the figure, then: ()

A, the density of liquid in Figure A is the largest; B, Figure B shows the highest density of liquid;

C. The density of liquid in Figure C is the highest; D, the density of Figure A and Figure B is the same. ..

10, as shown in the figure, A, B, C and D are four balls with the same volume and shape but different materials. According to the situation when they are still in the water, it can be judged that the lowest density is: ()

a，a； b，b； c，c； d d。

1 1, the following statement about leverage is correct: ()

A, hard straight rod is a lever; B, arm lever is neither labor-saving nor laborious;

C, the power arm of the laborious lever is longer than the resistance arm; D, the straight line from the fulcrum to the resistance point is called the resistance arm.

12, as shown in the figure, the ratio of the force arm of the spring scale to the hook code force arm to the lever tension is 5:2, and the reading of the spring scale is 4 n. If the lever weight is ignored, the hook code weight is ().

A, 10 cattle; B, 4 cows; C, 2.5 cattle; d， 1.6 N。

13, when lifting the same weight to the same height with devices A and B shown in the figure respectively: ()

A, hanging heavy objects with equipment A is more labor-saving than with equipment B;

B, it is more labor-saving to hang heavy objects with equipment B than with equipment A;

B, using device A or device B to lift the heavy object with the same pulling force;

D, using device B to lift the heavy object, and the power moving distance is less than that of device A. ..

14, which of the following is not gravity work? :( )

A, ripe apples fall from the village to the ground; B, the plane flies horizontally at high altitude;

C. Stones thrown vertically upwards are thrown vertically downwards; D. The glass ball put into the pool slowly sinks.

15. For the use of pulley blocks, the following statement is correct: ()

A, you can save labor, but you must change the direction of the force; B, can save labor, but can't change the direction of the force;

C, it can save manpower and distance at the same time; D, you can save labor and change the direction of force at the same time, but you can't save distance at the same time.

16, when doing Torricelli experiment, if the glass tube is tilted, during the tilting process: ()

A, the length of the mercury column in the glass tube is always the same; B, the length of the mercury column in the glass tube becomes longer, and the vertical height remains unchanged;

C, the length and vertical height of the mercury column in the glass tube become larger; D, the length of the mercury column in the glass tube remains unchanged, and the vertical height becomes smaller.

17, the labor-saving lever in the following tools is: ()

A, tweezers; B. screwdriver; C, haircut scissors; D, fishing rod.

18, a piece of wood floats on the water, and its volume is 1/4. If this exposed part is cut off, the remaining piece of wood will be: ()

A, completely submerged in water; B, discharging water with a volume of 1/4 or more;

C, half above the water; D, 3/4 of the volume is above the water surface.

19 As shown in the figure, a heavy object is hung at point B of lever OA, and the end A is hung under slip ring M with rope. At this time, the OA is just horizontal, and the point A coincides with the center of the arc frame PQ, so when the slip ring M gradually slides from the point P to the point Q, the tension of the rope to the end A will be:

First, remain unchanged; B, gradually increase; C, gradually reduce; D, from big to small and then to big.

20. An iron box floats on the water. When the iron box inclines and sinks into the bottom of the container due to water inflow, then: ()

A, the water level in the container will drop; B, the water level in the container will rise; C, the water level in the container will not change;

D, unable to judge the change of water level.

2 1, put an object with a mass of 2 kg and a volume of 1.8 decimeter 3 into the water. When released, this object will:

A, floating; B. don't move; C. sinking; D, I can't be sure.

22. In the mountain climbing competition, it is known that the weight ratio of Party A and Party B is 3:2, and the time ratio used to climb the same mountain is 4: 3, so the strength ratio of Party A and Party B is: ()

a， 1:2； b，2: 1； c，8:9； d，9:8 .

23. For two machines, the efficiency of the first machine is 70% and that of the second machine is 50%, so: ()

A, using machines to do work is labor-saving; B, use B machine to do more work; C, using the machine to do work quickly; D none of the above statements are correct.

24. Under the tension of 200 Newton, the cart and cart with the mass of 100kg and 50 kg were pulled horizontally, and they all moved 10m along the direction of the force. It takes different time to pull the cart and pull the cart, so:

A, pulling a cart does more work; B, pulling the car does more work; C. Pulling a cart does as much work as pushing a cart;

D, cart and cart do work at the same speed.

Iii. Calculation problem: (* *15)

1, an aluminum block with a volume of 100 cm3 and a weight of 2.65n is hung on the spring scale. When all aluminum blocks are immersed in water in a cylindrical container with a bottom area of 0 .2 decimeter, the water will not overflow the container. Q:

(1) spring scale indication;

(2) The pressure at the bottom of the water container increases because the aluminum block is immersed in water.

2. As shown in the figure, the lever is in a state of balance, in which OA is long 1 m, OB is long 0.25 m, and the weight P is 58.8n. Regardless of the mass of pulley and lever, how much N does the weight G weigh? (2) How much force does the pulley suspension points D and C bear?

Iv. experimental questions: (* *10)

1, in the experiment of "measuring the mechanical efficiency of pulley block". (1), as shown in the figure, if the weight of the moving pulley is 5N,

If the weight of the heavy object is 100N, the pulling force is at least _ _ _ _ n (2). If the hook code is pulled up at a uniform speed 10 cm, the pulling force is _ _ _ n; Useful work is _ _ _ _ _ Joule; The total work is _ _ _ _ Joule; The mechanical efficiency is _ _ _ _ _.

2. In the experiment of "Research on Lever Balance", as shown on the right, the hook code is hung on both sides of the lever, and the position of the hook code is changed to keep the lever balanced in the horizontal position.

(1) According to the above diagram, the balance condition of the lever written by the symbols on the diagram is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _;

(2) According to the balance condition of the lever, when the lever is balanced, fill in the blanks in the table below:

Power supply (ox) power arm (cm) resistance (ox) resistance arm (cm)

0.98 4.0 8.0

1.47 2.45 6.0

2.0 1.96 4.0

Verb (abbreviation of verb) Q&A: (***5 points)

In the long jump, a long run-up is needed, which is beneficial to improve the long jump performance. Why?

Reference answer:

First, fill in the blanks:

1, objects, mutual 2, no external force, static, uniform linear motion 3, pressure effect,1.96×1054,760,1.013×100. The force acting on the object, the distance the object passes along the direction of the force is 8, equal to or equal to 9, and the static uniform linear motion is10,2,980.

Second, multiple-choice questions:

1、B 2、D 3、C 4、B 5、C 6、A 7、A 8、D 9、C 10、C 1 1、B 12、A 13、B 14、B 15、D 16、B 17、B 18

Third, the calculation questions:

1, (1) 1.67 Niu (2) 490pa2, (1)1/7. 6 cattle (2)29.4 cattle, 235.2 cattle.

Fourth, the experimental questions:

1，( 1)2 1 (2)25、 10、80% 2，( 1)f 1×l 1 = F2×L2(2) 1.96、 10、3.92。

Verb (short for verb) Questions and answers:

Tip: Run-up can make athletes have higher speed before landing. After an athlete takes off, he moves forward due to inertia, so the higher the run-up speed, the farther he jumps.