"The Force from the Earth" Familiar and Unfamiliar Forces PPT Courseware 5

Description

"The Force from the Earth" Familiar and Unfamiliar Forces PPT Courseware 5

1. What is gravity?

The force on an object due to the attraction of the earth

2. The size of gravity

Calculation formula G=mg (g=9.8N/kg)

3. Direction of gravity

The direction of gravity is always vertical downwards

4. The point of action of gravity—the center of gravity

quality

Mass refers to the amount of matter contained in an object. It is an attribute of an object that does not change with the shape or state of the object, nor does it change with the position of the object.

International unit: kg

Commonly used units: t 1t=1000kg

g 1g=0.001kg

practise:

1. The mass of classmate Zhang Hua is 50kg. How many cows does he weigh?

Wang Min's weight is 392N. What is his mass in kilograms?

2. Some people say: 1kg=9.8N. Is this correct? Why?

In general, g is a certain value. However, after precise measurements by scientists, there are still differences in g. The following table shows the g values ​​in different cities.

Observe and analyze the data and answer:

The cities with the same g value are ( );

The two places with the largest difference in g values ​​are ( )

The reason for the change in g value may be ().

Consolidation exercises

1..The force exerted on an object due to _______ is called gravity. The magnitude of gravity is referred to as _____. The object exerting force by gravity is _______.

2.g=9.8N/kg, its physical meaning is ______.

3. A brick is first placed flat on the ground, then placed sideways on the ground, and finally placed vertically on the ground. The position of its center of gravity will be ______. (Optional "increase" or "lower")

4. The gravity exerted by an object with a mass of 500 grams is _____N.

Improve ability

1. When the shot put is launched from the athlete's hand and flies in the air, if the air resistance is not considered, the shot put will ( )

A is only pushed by the hand. B is pushed by both gravity and push.

C is only affected by gravity D is not acted upon by any force

2. The gravity of an object on the moon is one-sixth of that on the earth. The mass of a person on the earth is 60kg. After arriving on the moon, his weight is ( )

A 98 N B 10kg C 588 N D 60kg

3. An object weighing 18 N rests on an incline. Draw a schematic diagram of the gravity exerted on the object.

4. Throw the basketball into the blue basket with a force of 40 N at an angle of 60 degrees to the ground. The gravity of the basketball is 15 N. Ignoring the resistance of the air, the force diagram shows the force on the basketball when it flies in the air.

weightlessness

We live on earth, and every move we make is affected by gravity. People have long been accustomed to it. What would our lives be like once gravity was lost?

Can you imagine what would happen if there was total weightlessness?

Under weightless conditions, any object can float in the air, and the liquid is absolutely spherical. Astronauts are as comfortable sleeping standing up as sleeping lying down. Be careful when walking. If you are not careful, you will "not reach the sky or the ground." . Food should be made into lumps and toothpaste-like paste to prevent food debris from "floating" in the air and entering the astronauts' eyes and nostrils...

You can continue to use your imagination to cite more phenomena...

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Update Time: 2024-07-29

This template belongs to Physics courseware Shanghai Science Edition 8th Grade Physics industry PPT template

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