"Average Speed ​​and Instantaneous Speed" Simple Movement of Matter PPT Courseware 4

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"Average Speed ​​and Instantaneous Speed" Simple Movement of Matter PPT Courseware 4

1. Variable speed linear motion

Definition: An object moves in a straight line if its displacements are not equal in equal times. This kind of motion is called variable speed linear motion.

understand:

1) The displacements do not have to be equal in any equal time

2) Objects that move in a straight line can only move at a constant speed and at a variable speed;

3) There are many forms of variable speed linear motion.

2. Average speed

(1) Example: A train moving on a straight road has a displacement of 34km in 20 minutes. Among them, the displacement in the first 8 minutes is 16km, and the displacement in the last 12 minutes is 18km. There are also speeds in between.

Discovery: Since it is a variable-speed linear motion, the speed of the movement in these 34 minutes is very variable. Of course, the movement may be faster at some point in the last 12 minutes, but in general (on average), the movement speed in the first 8 minutes The exercise must be faster than the exercise within the next 12 minutes! How can you tell? Just look at s/t! That is, if s/t is large, the average within s (or within t) will be faster. In physics, s/t is called the average speed averaged within s (or within t)! Represented by v.

(2) Definition: v=s/t

question:

①Using the definitions, can we find v for the above two processes? What do the results show?

②Is the displacement in the first 8 minutes and the first 4 minutes 8km? !

(3) Note:

①The average velocity is also a vector, and the direction is the corresponding displacement direction, not necessarily the direction of motion;

②The average speed is related to which segment, but the average speed of uniform linear motion has nothing to do with which segment;

③The average speed is generally not the average speed of the corresponding process

④ The average speed can only roughly reflect the overall speed of a certain segment, but the movement conditions are still unknown.

1. An object moves at a uniform speed with a speed υ=2m/s, then:

1) = within the first 2s? 2) The υ at the end of 2s is =?

2. An object begins to move in a variable speed linear motion from rest. It is known that when a displacement of 12 m occurs in the first 4 s, the speed reaches 8 m/s, and then it moves at a constant speed for 3 s, and then passes through a displacement of 20 m at an average speed of 10 m/s. ask:

1) = within the first 4 seconds?

2) Instant υ= at the end of 6s?

3) = within the first 7s?

4) The whole process =?

5) It is known that the average speed in the last 0.5s is 15m/s, what is the average speed in the previous 1.5s?

3． A particle moves sequentially on straight line ABC. It is known that: the average speed of segment AB is _____, the average speed of segment BC is _____, and the corresponding times are t1 and t2, then:

1) Average speed of AC segment =?

2) If AB=BC, it is represented by _____, _____

3) If t1=t2, it is represented by _____, _____

4) If AB=3·BC or t1=1/3·t2, what about the average speed of segment AC?

4. In a 100-meter race, an athlete's speed at the end of 3 seconds after starting is 8m/s, and the speed when he reaches the finish line at the end of 10s is 13m/s. His average speed throughout the entire race is:

A. 11 m/s b． 10.5 m/s c． 10 m/s D． 9.5 m/s

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"Average Speed ​​and Instantaneous Speed" Simple Movement of Matter PPT Courseware 3:

"Average Speed ​​and Instantaneous Speed" Simple Movement of Matter PPT Courseware 3 Knowledge Review: Teachers and friends check each other for 1 minute, and then the whole class communicates 1. There are two ways to compare the speed of an object: ___________ and ___________ 2. In Physics ,Bundle_______________..

"Average Speed ​​and Instantaneous Speed" Simple Movement of Matter PPT Courseware 2:

"Average Speed ​​and Instantaneous Speed" Simple Movement of Matter PPT Courseware 2 Look at the pictures and analyze the questions. What kind of exercise do the athletes and swimmers in the 100-meter race do? How to compare their speed? Summary: Variable speed motion is more complicated than uniform speed motion. Unless it is very precise,...

"Average Speed ​​and Instantaneous Speed" Simple Movement of Matter PPT Courseware:

"Average Speed ​​and Instantaneous Speed" Simple Movement of Matter PPT Courseware [Experience] Observe changes in the speed of movement of objects Activity 1: Observe a car driving smoothly on a straight road. Activity 2: Let the ball fall still from a certain point as shown in the picture. (1) In activity 1..

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Update Time: 2024-08-31

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