"Gravity" force PPT (the direction and center of gravity v in Lesson 2)

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"Gravity" force PPT (the direction and center of gravity v in Lesson 2)

Part One Content: Basic Knowledge Key Points

Knowledge point 1: The direction of gravity

1. The heavy vertical line that can be used to check whether the walls are vertical when building a house is made based on the property that the direction of gravity is vertically downward.

2. As shown in the picture is Xiao Ming’s self-made level. Use it to check whether the desktop is level. When Xiao Ming used the level at a certain time, he placed it on a level desktop. As shown in the picture, the left end of the desktop (optional) "Left end" or "right end" ) is higher.

3. An iron ball rolls down an incline. The correct direction of gravity on the iron ball is (B)

Knowledge point 2: focus

4. Regarding the center of gravity of an object, which of the following statements is incorrect (A)

A. The center of gravity of all objects is in its middle position

B. The center of gravity of all objects is the point of action of gravity on the object.

C. The center of gravity of an object is not always on the object

D. The center of gravity of an object with uniform texture distribution and regular shape is at its geometric center.

5. As shown in the picture, the toy "tumbler" will automatically stand up after being knocked down. The secret is (C)

A. Gravity is small and can be ignored

B. The direction of gravity is always vertical downwards

C. Low center of gravity, not easy to tip over

D. There is an automatic lifting device inside

Gravity PPT, Part 2: Comprehensive Ability Improvement

6. After 20 cm is cut off from the left end of an iron rod of uniform thickness, its center of gravity moves 10 cm to the right end.

7. As shown in the figure, use your finger to press a certain point on the scale to balance the scale. This point is the center of gravity of the scale.

8. The acrobat who performs tightrope walking always holds a wooden stick in his hand. He is using it to adjust his center of gravity. When he falls to the right, he must send the wooden stick to the left in time to stabilize himself. fall. This also shows that the point of action of force will affect the effect of force.

9. As shown in the figure, there is a bubble in the level tube of the level. When the level tilts, the bubble in the level tube will move to one end, thereby determining the position of the horizontal plane. If the bubble moves to the side A, then the tested plane A (optional "A" or "B") has a higher end.

10. Place a brick flat on the ground first, then place it sideways on the ground, and finally place it vertically on the ground, then (C)

A. The height of the center of gravity remains unchanged and the magnitude of gravity remains unchanged.

B. The height of the center of gravity decreases and the magnitude of gravity decreases

C. The height of the center of gravity increases and the magnitude of gravity remains unchanged.

D. The height of the center of gravity increases and the magnitude of gravity increases

11. As shown in the picture, when traveling and mountaineering, the items in the backpack may be light or heavy. If you want to prevent people from falling backward easily, the way to place the items in the backpack is (B)

A. Place heavy items in the lower part of the backpack

B. Place heavy items on the upper part of the backpack

C. Place heavy items in the middle of the backpack

D. You can place it anywhere you like

Gravity PPT, the third part: expansion, exploration and breakthrough

18. We usually call the degree of stability of an object on a support surface stability. The greater the stability, the less likely the object will fall over. Buildings, machines, vehicles, ships, aircraft, instruments, etc. all have stability problems. There are two main ways to improve stability: one is to increase the support surface; the other is to lower the center of gravity. The figure shows several examples of improving stability.

(1) Among the several examples shown in the figure, those who use the method of increasing the support surface to improve stability are A and C; those who use the method of lowering the center of gravity to improve stability are B;

(2) There are many objects around you that use the above method to improve stability. Can you give an example of each? Examples of using the method of increasing the support surface to improve stability include floor fans with larger bases ( Reasonable as long as it is reasonable); An example of using the method of lowering the center of gravity to improve stability is an acrobat hanging a heavy object under a unicycle pedaled at high altitude (reasonable as long as it is reasonable).

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Update Time: 2024-11-20

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

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