"Gong" Work and mechanical energy PPT download

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"Gong" Work and mechanical energy PPT download

Part One Content: Basic Knowledge Key Points

Knowledge point 1 Work in mechanics

1. As shown in the figure, the ball is released from rest at point A. The ball will automatically swing from point A to point B. During this process, the pulling force of the string (without deformation) acting on the ball will not affect the ball. Do (optional "do" or "don't do") work.

2. In the four scenarios shown in the figure, the work done by people on the object is (B)

Knowledge point 2 Calculation of work

3. "Tower crane" is a lifting equipment commonly used on construction sites. The "tower crane" first lifts the 8000 N steel vertically upward for 8 m at a constant speed. During this rising process, the work done by the "tower crane" on the steel is W1 = 6.4×104 J; then it moves 3 m in the horizontal direction. During the horizontal movement, the "tower crane" performs work on the steel W2 = 0 J.

4. On a level ground, use a pulling force of 50 N to pull a car weighing 200 N forward 4 m in the horizontal direction. After the pulling force is removed, the object still slides forward 1 m. During the whole process, the pulling force does 200 J and the gravity does work. 0J.

5. Xiao Cong picked up the physics textbook that fell on the ground and put it back on the table. The work done is closest to (C)

A.0.02 J B.0.2 J

C.2 J D.20 J

Performance PPT, part 2: improvement of comprehensive abilities

6. As shown in the figure, the magnitude of the pulling force F is 20 N, and an object weighing 50 N is pulled to perform uniform circular motion on a smooth horizontal surface. If the rope is 0.5 m long, the object moves in one circle, and the work done by the pulling force is 0J.

7. The barrel of a rifle is 0.5 m long, and the average thrust of gunpowder on the bullet is 500 N. If this rifle hits a target 100 m in front, the work done by the thrust on the bullet is 250 J.

8. In the physical education test of the high school entrance examination, Xiaofang threw a medicine ball with a force of 60 N and drew a beautiful arc in the air. If the weight of the solid ball is 20 N, Xiaofang throws it to a distance of 6.3 m, and the highest point of the ball is 2.6 m from the ground, then the work done by gravity while the ball is flying in the air is 52 J.

9. The iron block shown in Figure A has a gravity G=4 N and is adsorbed on a vertically long magnetic plate. When it moves upward under the action of a pulling force F=6 N in the vertical direction, the iron block The friction force received is 2 N; the relationship between the speed v of the iron block and time t is shown in Figure B. Then the work done by the pulling force F within 4 s is 4.8J.

10. Among the following statements about work done by force, which one is correct (C)

A. When lifting the bucket from the first floor to the second floor, the force of lifting the bucket does no work on the bucket.

B. Standing on a level road holding a bucket, the force of lifting the bucket does work on the bucket

C. Push the bicycle forward in the horizontal direction, and the force of the pusher does work on the bicycle.

D. When the thrown basketball is flying in the air, the push of the hand does work on the basketball.

11. In a billiards game, the player pushes the cue to hit the white ball. The white ball moves and then collides with other balls. The following statement is correct (B)

A. A ball rolling on a horizontal table is subject to gravity, and gravity does work on it.

B. When the hand pushes the club forward, the hand does work on the club

C. The tabletop’s support for the ball has done some work

D. The white ball does not stop after hitting the black ball because the human hand is still doing work on the white ball.

PPT, the third part: Expand, explore and break through

17. As shown in the figure, the gravity exerted by object G is 40 N.

(1) Under the action of pulling force F1, the object is made to rise 0.5 m at a constant speed in the vertical direction. Find the work done by pulling force F1 on the object during this process;

(2) If the object is placed on a smooth inclined plane with an inclination angle of 30°, and a pulling force F2 parallel to the inclined plane is used to make the object move upward at a constant speed 1 m along the inclined plane, the magnitude of the pulling force F2 at this time is exactly 20 N. Find the value of the pulling force F2 at The work done on the object during this process;

(3) Comparing the above two situations, what conclusion can you draw?

Solution: (1) The work done by the pulling force F1 is W1=F1h=40 N×0.5 m=20 J

(2) Work done by pulling force F2 W2=F2s=20 N×1 m=20 J

(3) For the same object to rise to the same height, the work required to be done on it is equal (or using an incline can save effort, but not work, as long as it is reasonable).

Keywords: Free download of PPT courseware for the second volume of eighth-grade physics published by the People's Education Press, download of work PPT, download of work and mechanical energy PPT, .PPT format;

For more information about the PPT courseware "Work and Mechanical Energy", please click on the Work and Mechanical Energy ppt Work ppt tab.

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Update Time: 2024-11-22

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

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