"Power" Power PPT

Description

"Power" Power PPT

Part One: Preview Perception

1. Force

1. Concept: Force is the _______ of an object on an object.

2. The two objects that act are one is a _______ object and the other is a _______ object.

3. Unit of force: _______, abbreviated as _______, symbol _______.

2. Effect of force

1. Force can cause objects to _______.

2. Force can change the ______________ of an object.

3. Representation of force

1. The three elements of force: _______, _______, and ______________.

2. Schematic diagram of force

(1) Concept: Use a ____________________ to represent force.

(2) Method: Draw a line segment along the direction of the force. The length of the line segment represents the _______ of the force. Draw an arrow at the end of the line segment to represent the _______ of the force. Use the starting point or end point of the line segment to represent the _______ of the force.

4. The effects of forces are mutual

1. When one object exerts a force on another object, the other object also _______________ it.

2. The effect of force between objects is ______________.

Power PPT, Part 2: Interactive Classroom Understanding

How to draw force diagram

(1) How to draw a schematic diagram of force

Determine the force-bearing object↓

Determine the point of action of the force↓

Draw a line segment along the direction of the force↓

Draw an arrow at the end of the line segment↓

Label the nature and magnitude of the force next to the arrow

(2) Precautions

①The point of action of the force must be drawn on the object, usually the contact point between the object exerting the force and the object receiving the force.

② The length of the line segment is not required to be strictly proportional to the magnitude of the force. A larger force on the same graph should be represented by a longer line segment.

[Example] The little girl lifts the bucket with a force of 80 N (as shown in Figure A). Please draw a schematic diagram of the force of the little girl lifting the bucket in Figure B.

Instructions According to the meaning of the question, determine the three elements of force.

Power PPT, the third part: try the application

1. Force

1. When force occurs, which of the following statements is correct ()

A. There can be no object, neither a force-exerting object nor a force-receiving object.

B. As long as there is a force-receiving object, there is no need for a force-exerting object.

C. As long as there is a force-exerting object, it doesn’t matter whether there is a force-receiving object or not.

D. There must be both a force-receiving object and a force-exerting object. Without the object, there is no force function, and there is no force.

Analysis This question will be analyzed starting from the concept of force. Force is the effect of an object on an object. When a force acts, the force-exerting object and the force-receiving object always appear at the same time. The concept of force emphasizes object versus object, which means that when force appears, there cannot be only one object. Without the object, there is no existence of force.

2. Which of the following objects is lifted with a force closest to 3 N()

A. A calf

B. Two eggs

C.Eighth grade physics textbook

D. Two 1 yuan coins

Analysis The force used to hold up two eggs is about 1 N, B is wrong; the force to hold up a calf is much greater than 3 N, A is wrong; the force to hold up two coins is greater than the force to hold up one egg. Small, D is wrong; the force holding up the eighth grade physics textbook is about 3 N, C is right.

2. Effect of force

3. The scenes in Figures A, B, C, and D represent the effects of force. Among them, the main ones that show that force can change the motion state of an object are ()

A.A and B B.C and D

C.A and C D.B and D

4. During the skiing competition in the Winter Olympics, athletes used their ski poles to accelerate down the mountain from rest. This shows that force can change the _______________ of an object. The scene when an athlete collides with the sign pole while sliding down is shown in the figure. It shows that force can also cause changes in objects.

Analysis There are two effects of force. One is to change the motion state of an object, and the other is to change the shape of an object. When an athlete uses a ski pole to accelerate down the mountain from a standstill, the object's speed changes, that is, the object's state of motion changes. The shape of the object changes when the athlete collides with the sign pole while sliding down.

Answer state of motion shape

3. Three elements of force

5. As shown in the figure, use equal forces to pull and compress the same spring. This experiment shows that the effect of spring force is the same as ()

A. Depends on the size of the force B. Depends on the point of action of the force

C. Depends on the direction of the force D. Depends on the force-bearing area

Analysis From the picture in the question, we can see that when you pull the spring to the right, the spring becomes longer; when you press the spring to the left, the spring becomes shorter. It can be seen that when the magnitude of the force and the point of action of the force are the same, the direction of the force is different, and the effect of the force is different. So choose C.

6. As shown in the figure, when opening the door, it is easier for a person to push at point A on the edge of the door than at point B in the middle of the door. This shows that the effect of force is related to the _________ of force.

Analysis This question examines the three elements of force. To answer this question, it is necessary to clarify that the three elements of force are the magnitude, direction and point of action of the force. The three elements of force can all affect the effect of force. Analysis of the meaning of the question shows that this question changes the point of action of force and affects the effect of force.

Answer point of action

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Update Time: 2024-09-09

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

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