"Exploration - Comparing the Speed ​​of Movement of Objects" Simple Movement of Matter PPT Courseware 3

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"Exploration - Comparing the Speed ​​of Movement of Objects" Simple Movement of Matter PPT Courseware 3

According to the shape of the movement route:

linear motion

curved motion

According to whether the speed changes:

uniform motion

variable speed movement

In a 100-meter race, how do spectators compare the speed of athletes? How do referees compare the speed of athletes?

The method used by the audience is to compare who is running ahead, that is, "who has traveled a longer distance and who moves faster in the same time."

The method used by the referee is to see who reaches the finish line first, that is, "whoever travels the same distance takes less time and who moves faster."

Summary: Two ways to compare the speed of an object’s movement:

1. In the same time, the longer the distance an object travels, the faster it moves.

2. The less time it takes an object to travel the same distance, the faster it moves.

language expression exercises

Among the three students A, B, and C, who moves the fastest? Why?

In the same time, Student C traveled the longest distance, so Student C moved the fastest.

Who among the three students A, B, and C moves the fastest? Why?

Through the same distance, Student A takes the least time, so Student A moves the fastest.

1. Speed

(1) Physical meaning: Speed ​​indicates how fast an object moves.

Fast movement - means high speed;

Slow movement - means small speed

(2) Definition: The distance traveled by an object in unit time is called speed.

(3) Definition:

Speed=distance/time v=s/t

(4) Speed ​​unit:

SI unit: meter/second m/s

Commonly used units: kilometers/hour km/h

Unit conversion: 1 meter/second =? km/h

The difference between the definition of speed and its physical meaning

1. Definition: The distance traveled by an object in unit time

2. Physical meaning: describes the speed of object movement

2. Uniform linear motion

If an object moves in a straight line and its velocity remains constant, the motion is called uniform straight line motion.

in conclusion:

(1) For an object moving in a straight line at a uniform speed, its speed has nothing to do with the distance it travels and the time it takes. It is always a fixed value.

(2) For an object that moves in a straight line at a uniform speed, the distance it travels is proportional to the time it takes.

Example 1

During a project to build a winding mountain road, I encountered a huge boulder and planned to use blasting to blow it up. Construction workers used a 96-centimetre-long fuse to detonate the explosive. The burning speed of the fuse is 0.8 cm/s. After the igniter lights the fuse, he immediately runs away at a speed of 5 m/s. Can he run 500 meters to the safe zone before the explosive explodes?

Analysis: Method 1: Find the time t1 it takes for the fuse to burn out and the time t2 it takes for the igniter to run to the safe zone. Compare the sizes of t1 and t2. If t2

Method 2: First find the time t it takes for the fuse to burn out, and then find the distance s traveled by the igniter within time t. If s>500 meters, it means that the igniter has reached the safe zone before the explosion.

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"Exploration - Comparing the Speed ​​of Movement of Objects" Simple Movement of Matter PPT Courseware 6:

"Exploring and Comparing the Speed ​​of Movement of Objects" Simple Movement of Matter PPT Courseware 6 Activity: Compare the speed of falling pieces of paper Discuss: 1. How to compare the speed of their movement? Let them be released at the same time from the same height. The piece of paper that hits the ground first moves faster (the same distance is faster than...

"Exploration - Comparing the Speed ​​of Movement of Objects" Simple Movement of Matter PPT Courseware 5:

"Exploring and Comparing the Speed ​​of Movement of Objects" Simple Movement of Matter PPT Courseware 5 Under normal circumstances, which of the above three means of transportation runs faster? To compare the speed of motion in physics, the audience method is used and an important physical quantity speed is introduced. A: Small...

"Exploration - Comparing the Speed ​​of Movement of Objects" Simple Movement of Matter PPT Courseware 4:

"Exploring and Comparing the Speed ​​of Movement of Objects" Simple Movement of Matter PPT Courseware 4 Question 1 In a 100-meter race, athlete A completes the distance in 10 seconds, and athlete B completes the distance in 11 seconds. Which athlete runs faster? Question 2: Car A travels 80km in 2 hours, and Car B...

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Update Time: 2024-11-17

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