"Test in this Chapter" Simple Machinery PPT

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"Test in this Chapter" Simple Machinery PPT

1. (Kunming High School Entrance Examination) As shown in the figure, the lightweight lever OA can rotate around point O without friction. An object weighing 20 N is hung at point A. A vertical upward force F is added to point B. The lever is horizontal The position is balanced, and OB:AB=2:1. Then F = 30 N, which is a laborious lever.

2. (Liangshan Prefecture High School Entrance Examination) As shown in the figure, an iron rod with uniform mass is folded into a right angle in the ratio of 4:3, and one end is fixed on the wall with a hinge. The iron rod can rotate around point O. This rod weighs 70 N. To keep the rod balanced at the position shown in the figure, the minimum force applied to end A is 40 N.

3. (Yueyang High School Entrance Examination) Use a pulley block excluding rope weight and friction to lift the cargo weighing 720 N by 10 m at a constant speed. The total work done is 12000 J. At this time, the mechanical efficiency of the pulley block is 60%; use this pulley block to lift more For heavier objects, the mechanical efficiency will increase (select "get smaller", "unchange" or "get bigger").

4. (Guiyang High School Entrance Examination) People use different simple machines to assist work. When using the following simple machines normally, the correct statement is (A)

A. Chopsticks can save distance B. All scissors must save effort

C. The fixed pulley can save labor. D. The shorter the crowbar is, the easier it will be.

5. (Xiangxi Prefecture High School Entrance Examination) As shown in the picture, the big bear and the little bear sit on the seesaw. If their feet are not touching the ground and the seesaw is balanced in a horizontal position, which of the following statements is correct (C)

A. The gravity of the big bear and the little bear is equal

B. The distance between the big bear and the little bear to the fulcrum is equal

C.The product of their respective gravity and their respective moment arms is equal

D. All the above statements are correct

6. (Guigang High School Entrance Examination) The same pulley uses two devices A and B as shown in the figure to lift two objects A and B with a weight of 10 N at a constant speed. It is known that the pulley weighs 1 N, and the friction of the rope weight and the pulley is ignored. Then the correct one of the following statements is (B)

A. Hand pulling force F B = 10 N

B.The resultant force on object A is equal to the resultant force on object B.

C. If both objects A and B are lifted by 0.5 m, then device B will do more useful work.

D. If both objects A and B are lifted by 0.5 m, then the work done by F A due to the pulling force of the hand is more than that done by F B.

7. (Taian High School Entrance Examination) Picture A is a schematic diagram of a study group's "Measuring the Mechanical Efficiency of the Pulley Block". Use the spring dynamometer to pull the free end of the rope vertically upward to lift the object weighing 4.5 N from position A to position A'. At the same time, the spring dynamometer rises from position B to position B' in the figure. During this process ,The indication of the spring dynamometer is shown in Figure B. Please complete the following questions based on their experiments: (1) The height of the object lifted is 5.0 cm, the pulling force is 2 N, and the mechanical efficiency of the pulley set is η = 75%;

(2) If a movable pulley is added to the device in Figure A and changed to the device shown in Figure C to lift the same object, the mechanical efficiency of the pulley group will become smaller (optional "get bigger", "get smaller" or "not"). Change" ).

8. (Changchun High School Entrance Examination) During the construction of the Changchun East Bridge, the crane lifted the steel material with a mass of 4.5×103 kg by 2 m at a constant speed in the vertical direction, and the work done by its motor was 2×105 J ( g Take 10 N/kg). beg:

(1) The useful work done by the crane on the steel;

(2) Mechanical efficiency of the crane.

Keywords: Free download of PPT courseware for the second volume of eighth-grade physics published by the People's Education Press, download of test PPT in this chapter, download of simple machine PPT, .PPT format;

For more information about the PPT courseware "Simple Machinery Test in this Chapter", please click the "Simple Machinery PPT Test in this Chapter" PPT courseware.

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Update Time: 2024-06-28

This template belongs to Physics courseware People's Education Edition Physics for Grade 8, Volume 2 industry PPT template

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