"Speed" description of movement PPT download

Description

"Speed" description of movement PPT download

Part One: Curriculum Standard Requirements

1. Understand the physical meaning of average speed and instantaneous speed, and be able to distinguish between average speed and instantaneous speed.

2. Know the difference between instantaneous speed and instantaneous rate, and be able to use limit thinking to calculate instantaneous rate.

3． Understand average speed and average velocity and know the difference between them.

4． Be able to distinguish whether "speed" in daily life refers to speed or velocity.

Speed ​​PPT, Part 2: New textbook for self-study

1. Average speed

1. Fill it out

(1) Definition: The ratio of ____ of object motion to the ____ used, usually expressed by v, then v=st.

(2) Physical meaning: roughly describe the ____ and ____ of the movement of objects within a period of time.

(3) Unit: m/s in the International System of Units. Commonly used units include km/h, 1 m/s=____km/h.

(4) Direction: The average velocity is a vector, which has both magnitude and direction. Its direction is the same as the direction of ____.

(5) Average velocity: the ratio of ____ of an object’s motion to the elapsed time.

2. Give a verdict

(1) The average speed of an object within a certain period of time must be equal to its average speed. ( )

(2) The average speed of an object may be greater than its average velocity. ( )

(3) The average speed of uniform linear motion is equal to its average velocity. ( )

3． Choose one

(1) The speed mentioned in the following options refers to the average speed ()

A. Olympic 100-meter champion Bolt sprints at 11.5 m/s

B. High-speed trains can reach speeds of up to 350 km/h, and the shortest time from Beijing to Shanghai is only 4 hours and 18 minutes.

C. The bus travels from Qingdao to Jinan at a speed of 70 km/h

D. The moment the bullet exits the barrel, the speed can reach 800 m/s

(2) Xiaomeng rides a bicycle and moves in a straight line from rest. The displacements he passes in the 1st s, the 2nd s, the 3rd s, and the 4th s are 1 m, 2 m, 3 m, and 4 m respectively. ,but()

A. His instantaneous speed at the end of 4 s is 4 m/s

B. His average speed in 2 s is 1.5 m/s

C. His average speed in 4 s is 2.5 m/s

D. His speed at the end of 1 s is 1 m/s

2. Instantaneous speed

1. Fill it out

(1)Definition: The ____ of a moving object at a certain moment or position.

(2) Physical meaning: Accurately describe the speed and direction of movement of an object in a certain ____ or a certain ____.

(3) Direction: The instantaneous speed is ____, which has both magnitude and direction. Its direction is the same as the ____ direction of the object.

(4) Measurement of instantaneous speed:

①Principle: Replace with the size of ____ in a very short period of time.

②Method:

a. Photoelectric door method. The photoelectric gate experimental device can be used to measure the ____ of an object in a very short time, and it is considered to be the measured ____.

b. Speedometer method. A speedometer can be used to directly read the instantaneous speed of an object at a certain moment or position____.

(5) Instantaneous rate: The ____ of the instantaneous speed is called the instantaneous rate, or ____ for short.

Speed ​​PPT, the third part: improving new knowledge

Breakthrough point 1: Understanding average speed and instantaneous speed

1. v=st is the definition of speed, not the determinant. It cannot be considered that speed is directly proportional to displacement and inversely proportional to time.

2. When an object moves in a straight line, the direction of the speed can be expressed by positive or negative signs. When the direction of the speed is the same as the specified positive direction, it takes a positive value, and when it is opposite, it takes a negative value.

3． The instantaneous speed can be regarded as the average speed within t→0, but the physical meanings of the two are different. The average speed describes the speed of movement within a certain period of time, and the instantaneous speed describes the speed of movement at a certain moment.

4． There is no necessary relationship between the average speed and the instantaneous speed. An object with a large instantaneous speed does not necessarily have a large average speed.

[Typical Example 1] [Multiple Choices]The speed mentioned below refers to the average speed ()

A. Athletes in the 100-meter race cross the finish line at a speed of 9.5 m/s

B. The speed of the accelerated train reaches 150 km/h

C. Due to the traffic jam, the speed of the car in the tunnel is only 1.2 m/s

D. The space capsule returning to the ground fell into the Pacific Ocean at a speed of 8 m/s

[Regular method]

(1) Speed ​​is a physical quantity that describes how fast an object moves. It is a vector, with both magnitude and direction.

(2) The comparison of velocity depends on its absolute value, and the direction of velocity is the direction in which the object moves.

[Practice clearly]

1. [Multiple choice]Which of the following statements about speed is correct ()

A. Speed ​​is a physical quantity that expresses how fast an object moves. It has both size and direction. It is a vector.

B. The average speed has only magnitude but no direction, it is a scalar quantity

C. The car passes a certain road sign at speed v1, and the bullet is shot from the muzzle at speed v2. Both v1 and v2 refer to the average speed.

D. The speed of a moving object at a certain moment (or passing a certain position) is called instantaneous speed, which is a vector

Speed ​​PPT, Part 4: Training new literacy

1. Displacement sensor measures speed (scientific exploration of core literacy)

The figure is a schematic diagram of using a displacement sensor to measure speed. This system consists of a transmitter A and a receiver B. The transmitter A can transmit infrared and ultrasonic signals, and the receiver B can receive infrared and ultrasonic signals. Transmitter A is fixed on the moving object being measured, and receiver B is fixed on the table or slide rail. During measurement, A emits an infrared pulse and an ultrasonic pulse to B at the same time (that is, a beam of infrared rays and a beam of ultrasonic waves of very short duration). B starts timing when it receives infrared pulses and stops timing when it receives ultrasonic pulses. Based on the time difference between the two and the speed of sound in the air, the computer automatically calculates the distance between A and B (the propagation time of infrared rays can be ignored).

After a short period of time Δt, the sensor and computer system automatically perform a second measurement to obtain the new position of the object. Calculate the two position differences, that is, the displacement Δx of the object's movement. The system calculates the speed v according to v = ΔxΔt and displays it on the screen.

Is the speed measured in this way the average speed of transmitter A or the instantaneous speed? To measure the instantaneous speed of transmitter A, what requirements do you think should be met?

2. Discover good classic questions and practice the classic questions so that one can be as good as ten

It took 5 seconds for the car to stop from braking. During this period, the distances the car traveled every 1 s were 9 m, 7 m, 5 m, 3 m, and 1 m respectively (as shown in the figure).

(1) Find the average speed of the car in the first 1 s, the first 2 s, the first 3 s, the first 4 s and the entire journey. Of these five average speeds, which one is closest to the instantaneous speed when the car first brakes? Is it slightly larger or smaller than this instantaneous speed?

(2) What is the average speed of the car during the last 2 s of motion?

Keywords: Free download of PPT courseware of Lu Ke version of high school physics compulsory course I, speed PPT download, description of motion PPT download, .PPT format;

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Update Time: 2024-09-18

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