"Speed ​​of Movement" Mechanical Movement PPT Courseware 6

Description

"Speed ​​of Movement" Mechanical Movement PPT Courseware 6

learning target

Ability to describe the movement of objects using speed

Ability to perform simple calculations using speed formulas

Understand the concept of uniform linear motion

Understand the concept of average speed

How to compare the speed of objects moving and understand the practical significance of the concept of speed

Men's 100m final results announced

Lane 1: 9.95 Jim Haynes (South Africa)

Lane 2: 9.93 seconds Calvin Smith (UK)

Lane 3: 9.90 Leroy Burrell (Russia)

Lane 4: 9.85 seconds Leroy Burrell (USA)

Lane 5: 9.77 Asafa Powell (Jamaica)

Lane 6: 9 seconds 84 Donovan Bailey (Canada)

Lane 7: 9 seconds 79 Maurice Green (France)

Lane 8: 9.78 Tim Montgomery (USA)

question

The school's 100-meter champion's time was 12 seconds, while the 24th Olympic Games' 10,000-meter champion's time was 28 minutes. How do we compare the speed of their movements?

If the time and distance are different, compare the distance traveled per unit time.

That is, the ratio of distance to time is used to express the speed of movement. --speed

speed

Physical meaning: a physical quantity that expresses how fast an object moves

(1)Definition: Ratio definition method of distance and time

(2) Speed ​​formula: V=s/t

Unit: m/s

Commonly used units: km/h

The walking speed of a person is 1.2m/s, which means: ______

1 Uniform linear motion: An object moves along a straight line with constant speed (fast or slow).

(Uniform linear motion is the simplest mechanical motion)

2 Variable speed motion: motion in which the speed of an object changes.

(The sports we see in daily life are basically variable speed sports.)

When an object moves at variable speeds, its speed is sometimes fast and sometimes slow. How to describe its movement?

Average speed: In variable speed motion, the total distance divided by the total time is called the average speed.

In variable speed motion, it can only roughly reflect the situation of variable speed motion.

Compliance testing

1. Speed ​​is a physical quantity that reflects the ____ of an object. In uniform linear motion, the speed is equal to the moving object ____, and the formula is ____. In the International System of Units, the unit of speed is ____, and other units are ____.

2. The moving speed of a train is 72km/h, and the flying speed of a swallow is 48m/s. The swallow moves ____ faster than the train.

3. A train takes 1.5 hours from point A to point B via 5 intermediate stations. It is known that the average speed of the train is 60km/h, and the distance between point A and point B is ____km.

4. The car traveled at a speed of 25m/s for 2 hours, and the distance it covered during this period was ____km; if it traveled at this speed, it would take ____h to cover a distance of 135km.

5. The ratio of the distance traveled by the two cars A and B is 6:5, the ratio of their moving time is 4:3, and the ratio of the moving speeds of the cars is ____.

【Extracurricular materials】

The first cosmic speed is 7.9km/s. It flies out of the atmosphere and circles the earth. The speed of the second universe is 11.2km/s and it flies out of the solar system. The third cosmic speed is 16.7km/s flying out of the Milky Way.

The first cosmic speed - firing a cannonball far away from the ground. The higher the speed of the cannonball, the farther it travels. When the cannonball reaches 7.9 kilometers/second, the cannonball no longer falls back to the ground (irrespective of atmospheric effects), but circles the earth. Flying in a circle is the first cosmic speed. As altitude increases, the Earth's gravity decreases, and the flight speed required to orbit the Earth also decreases. All spacecraft fly outside the atmosphere very high above the ground, so their flight speeds are lower than the first cosmic speed.

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Update Time: 2024-11-22

This template belongs to Physics courseware Lu Jiao edition eighth grade physics volume 1 industry PPT template

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