"Image pursuit and encounter problems in linear motion with uniform speed" Research on linear motion with uniform speed PPT

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"Image pursuit and encounter problems in linear motion with uniform speed" Research on linear motion with uniform speed PPT

Part One Content: High Frequency Test Point 1 Displacement-Time Image Problem

[Knowledge Comprehensive]

1. The displacement-time image reflects the change of displacement with time of an object moving in a straight line. The image is not the trajectory of the object's movement.

2. The displacement-time image can only describe the linear motion of the object. This is because the displacement-time image can only represent the two directions of the object's motion: the upper part of the t-axis represents the positive direction, and the lower part of the t-axis represents the negative direction; if the object moves in a curve , then the displacement-time image cannot be drawn.

3. The slope of each point on the displacement-time graph represents the velocity of the object at that moment. The magnitude of the slope represents the magnitude of the velocity. The positive and negative of the slope represents the direction of the velocity.

[Training Unicom]

[Typical Example 1] As shown in the figure, straight line a and curve b are the displacement-time (st) graphs of cars a and b running on a straight road respectively. The figure shows ()

A. At time t1, car a catches up with car b

B． At time t2, the two cars a and b move in opposite directions.

C. During the period from t1 to t2, the displacement of car b is larger than that of car a.

D． During the period from t1 to t2, the speed of car b is always greater than that of car a.

[Error-prone warning]

It is easy to choose C by mistake in this question. During the period from t1 to t2, except for the two moments t1 and t2, the position coordinates of car b are greater than the position coordinates of car a at any time. Therefore, it is easy to conclude that the displacement of car b is greater than the displacement of car a. wrong conclusion.

[Instant training]

1. As shown in the figure is the st image of a particle, it can be seen from the image ()

A. The particle moves in a straight line at a uniform speed within 0 to 40 s.

B． The direction of movement in the first 20 s is the same as the direction of movement in the next 20 s.

C. Do exercises that increase the speed in the first 20 s, and do exercises that decrease the speed in the next 20 s.

D． The first 20 s is a uniform motion, and the last 20 s is also a uniform motion, and the speeds are equal.

2. As shown in the figure is the displacement-time image of two objects A and B moving in a straight line. It can be seen from the image ()

A. When B starts moving, the two objects are 20 m apart.

B． The distance between objects A and B gradually increases

C. The two objects are farthest apart at 10 s and meet at 25 s.

D． A moves faster than B

PPT on the image pursuit and encounter problem of linear motion with uniform speed, part 2 content: High-frequency test point 2 speed-time image problem

[Knowledge Comprehensive]

1. The speed-time image reflects the law of the speed of an object moving in a straight line changing with time, and it can only describe the situation of an object moving in a straight line.

2. The slope of the tangent line at a certain point on the graph represents the magnitude of the object's acceleration, and the positive or negative slope represents the direction of the object's acceleration.

3. The area enclosed by the graph and the time axis represents the displacement within the corresponding time period. If the area is above the time axis, it means the displacement direction is positive; if the area is below the time axis, it means the displacement direction is negative.

[Training Unicom]

[Typical Example 2] Two objects A and B are moving in a straight line with uniform speed on the same straight line. Their velocity images are as shown in the figure, then ()

A. The moving directions of objects A and B must be opposite.

B． In the first 4 s, the displacements of objects A and B are the same.

C. When t=4 s, the speeds of the two objects A and B are the same

D． The acceleration of object A is greater than the acceleration of object B

[Regular method]

(1) The direction of the speed can be determined based on the positive and negative values ​​of v in the image.

(2) The direction of acceleration can be determined based on the positive and negative slope.

(3) The magnitude of acceleration can be determined based on the absolute value of the slope.

(4) According to the area enclosed by the graph and the time axis, the displacement within the corresponding time can be known.

[Instant training]

3. The picture shows the vt images of two objects a and b moving on the same straight line. It can be seen from the picture ()

A. Velocity is in the same direction, acceleration is in the opposite direction

B． The direction of velocity is opposite and the direction of acceleration is the same

C. The speed and acceleration directions are the same

D． The directions of speed and acceleration are opposite

4.[Multiple Choice]A car starts from point A and drives along the straight road to point B and just stops. Its speed image is as shown in the figure, then there are two periods of time 0~t and t~3t Within, the following statement is correct ()

A. The ratio of acceleration is 2:1

B． The ratio of displacement is 1:2

C. The ratio of average speed to size is 1:1

D． None of the above statements are correct

PPT on the problem of image pursuit and encounter in linear motion with uniform speed, the third part: High-frequency test point 3: Problems of pursuit and encounter

[Knowledge Comprehensive]

1. Follow up on issues

(1) Trace the two relationships that satisfy the problem

Time relationship: From the time the object behind catches up to the time it catches up with the object in front, the time elapsed by the two objects is equal

Displacement relationship s2 = s0 + s1, where s0 is the distance between the two objects when chasing begins, s1 represents the displacement of the object being chased in front, and s2 represents the displacement of the object chasing behind.

(2) Critical conditions: When the speeds of two objects are equal, situations such as catching up, avoiding collision, being farthest from each other, or being closest to each other may occur. That is, the critical condition for the above four situations is v1 = v2.

(3) Precautions: If the object being chased moves at a constant deceleration, be sure to pay attention to whether the object has stopped moving before catching up.

2. encounter problem

(1) Meeting conditions: objects moving in the same direction meet when they catch up; objects moving in opposite directions meet when the sum of the absolute values ​​of their respective displacements is equal to the distance between the two objects at the beginning.

(2) Critical state: The critical state to avoid collision is when two objects are in the same position and their relative speed is zero.

3. Problem-solving steps for catching up and encountering problems

(1) Based on the analysis of the movement process of the two objects, draw a schematic diagram of the movement of the objects.

(2) According to the motion properties of the two objects, list the displacement equations of the two objects respectively. Note that the relationship between the motion time of the two objects must be reflected in the equation.

(3) Find the correlation equation of the displacement of the two objects from the motion diagram.

(4) Solve the simultaneous equations and conduct a simple analysis of the results.

[Regular method]

Problem-solving skills for pursuit and encounter problems

(1) Pay close attention to "one picture and three formulas", that is, process diagram, time relationship, speed relationship and displacement relationship.

(2) When reviewing the question, you should grasp the key words in the question and fully explore the implicit conditions in the question, such as "just", "exactly", "at most", "at least", etc. They often correspond to a critical state and meet the corresponding critical conditions. .

PPT on the problem of image pursuit and encounter in linear motion with constant speed, Part 4: High-frequency test point 4: Using moving images to analyze pursuit and encounter problems

[Knowledge Comprehensive]

Applying moving images to solve problems "Six Looks"

[Training Unicom]

[Typical Example 4] [Multiple Choice]As shown in the figure is the displacement image of two people A and B moving on the same straight line. The following analysis of the image is correct ()

A. Within 0 to 2 s, two people A and B are walking in the same direction.

B． Within 0 to 2 s, the speed of A is smaller than the speed of B

C. In 5 s, A travels more distances than B

D． Within 5 s, the displacement of A is greater than the displacement of B

[Typical Example 5] As shown in the figure, the speed-time image of two particles A and B starting from rest and moving in the same direction from the same position. If the two images intersect at time t0, then the following judgment is correct ()

A. At time t0, two particles A and B meet.

B． Before the two particles meet again, the two particles are farthest apart at time t0.

C. Within the period 0 to t0, the acceleration of particle B’s movement at any time is greater than the acceleration of particle A.

D． Within the time period from 0 to t0, the average speed of point A is greater than the average speed of point B.

[Regular method]

Moving images can more intuitively reflect the changes in the displacement, speed (and acceleration) of objects over time. Therefore, moving images can be used to analyze pursuit and encounter problems. When solving problems, you should focus on obtaining the time relationship and displacement relationship between the movement of two objects based on the images. , speed relationship, etc.

Keywords: Free download of PPT courseware of Lu Ke Edition High School Physics Compulsory Course One, PPT download of image pursuit and encounter problem of uniformly variable linear motion, PPT download of research on uniformly variable linear motion, .PPT format;

For more information about the PPT courseware "Research on Uniform Speed ​​Linear Motion and the Problem of Image Chasing and Encounter in Uniform Speed ​​Linear Motion", please click the Research on Uniform Speed ​​Linear Motion ppt Image Chasing and Encounter Problem in Uniform Speed ​​Linear Motion ppt tag.

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Update Time: 2024-10-04

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