"Measuring Average Speed" Mechanical Motion PPT

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"Measuring Average Speed" Mechanical Motion PPT

Part One: Preview Perception

1. Average speed

By measuring the _____ of the object's motion and the _____ it takes to travel this distance, you can calculate the average speed of the object during this period of time.

2. Measurement of average speed

1. Experimental principle: __________.

2. Experimental equipment: inclined plane, trolley, wooden block, metal sheet, _____ and _____.

3. Experimental design plan: As shown in the picture, assemble the experimental device and use a wooden block to pad one end of the slope to make the slope between the slope and the horizontal plane _____.

Use _____ to measure the distance traveled by the car, and use _____ to measure the time it takes for the car to slide down the slope until it hits the metal piece, and then substitute it into the speed formula for calculation.

Measuring average speed PPT, part 2: interactive classroom understanding

Two ideas for studying changes in the speed of movement of objects

(1) Direct comparison. Measure the speed with a speed measuring instrument and compare directly.

(2) Indirect measurement. Divide the journey into several segments, use a scale to measure the length of each segment, use a stop watch to measure the time it takes for the object to pass through each segment, substitute it into the speed formula to calculate the speed, and finally compare the speeds.

[Example] The measuring tools required to measure the average speed of the car are __________ and __________. Picture A is an experimental process when measuring the average speed. The setting of the stopwatch in Picture B is "hour: minute: second". ①, ②, and ③ respectively correspond to the time of the car at the starting point, midpoint of the journey, and end point. The average speed of the car through the whole process v=__________m/s. The distance of s1 is exactly half of the total distance. The average speed of the car through the first half of the distance is v1=__________m/s.

Tip: To measure the average speed of a car moving on an incline, the distance and time must be measured. The idea of ​​​​this question is to read the corresponding time based on the given distance, and use the formula v=_____ to calculate the average speed. To find the average speed, be sure to divide the distance traveled within a period of time by the corresponding time.

Analysis: The tool for measuring distance is a scale, and the tool for measuring time is a stopwatch. The movement time of the car from top to bottom is t=5 s, and the total distance is s=0.9 m, so the average speed of the whole journey is

Measuring average speed PPT, Part 3: Try the application

1. Average speed

1. Regarding average speed, which of the following statements is correct ()

A. The average speed can accurately reflect the speed of an object’s movement

B. The average speed can only roughly reflect the speed of the object’s movement.

C. The average speed and instantaneous speed of uniform linear motion are not equal

D. None of the above statements are correct

The average speed can only roughly reflect the speed of an object's movement, while the instantaneous speed can accurately reflect the movement of an object. The speed of uniform linear motion does not change, so its average speed is the same as its instantaneous speed.

2. At the school sports meeting, Xiao Ming participated in the 100-meter race. After starting, Xiao Ming ran faster and faster, and finally won the championship with an excellent time of 12.5 seconds. Regarding the above process of Xiao Ming’s 100-meter race, which of the following statements is correct ()

A. Xiao Ming must have spent 6.25 s in the first 50 m.

B. The distance Xiao Ming travels per second is 8 m

C. Xiao Ming’s average speed is 8 m/s

D. Xiao Ming’s average speed is 8 km/h

3. In the experiment of measuring the average speed of an object, if the measured movement time of the object is larger than the actual value, the measured average speed of the object will be ()

A. Same as the actual value B. Larger than the actual value

C. Smaller than the actual value D. Uncertain

4. Two students were doing an experiment to measure the average speed of a car. The experimental situation is as shown in the figure.

(1) From the picture in the question, we can see that the time it takes for the car to pass through the first half and the whole journey is 3 s and 5 s respectively. The calculation shows that the time it takes for it to pass through the second half of the journey is 5 s-3 s=2 s. Use the speed calculation formula v= s/t can get the average speed of each segment. According to the calculated average speed of each section, the average speed of the car through the first half of the journey is smaller than the average speed of the second half of the journey. (2) When measuring the average speed of the car, the slope should be kept very small so that the car moves on the slope for a longer time. The movement time of the car can be measured more accurately to reduce errors.

(1)0.1　0.12　0.15　Less than (2)Very small Car movement time

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Update Time: 2024-09-29

This template belongs to Physics courseware People's Education Edition Physics for Grade 8, Volume 1 industry PPT template

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