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

Description

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

1. The concept of gravity

All objects will fall to the ground when they lose support. This is because the Earth has a gravitational pull on objects around it, pulling them toward the ground.

The force exerted on an object by the earth due to its attraction is called gravity

The object exerting force by gravity is the earth

2. Three elements of gravity

(1) The magnitude of gravity

⑴The gravity exerted by an object can be measured with a spring dynamometer

The magnitude of the gravitational force on an object is referred to as its weight.

⑵ Quality

The amount of matter contained in an object is called mass. It is represented by m

The unit of mass in the International System of Units is: kilogram

Commonly used units are: tons, grams

1 ton = 1000 kilograms 1 gram = 10-3 kilograms

⑶ Explore the relationship between gravity and mass

Design experiments to study factors affecting the magnitude of gravity

1. What is the purpose of designing the experiment clearly?

2. In what steps should the experiment be conducted?

3. What data should be recorded?

4. What conclusions can be drawn from analyzing the data?

(ii) Direction of gravity

The direction of gravity is always vertical downwards

think about it

The direction of gravity points to the center of the earth

(iii) The point of action of gravity

The point where gravity acts on an object is called the center of gravity

The center of gravity of an object with regular shape and uniform mass distribution is at its geometric center

The center of gravity of a record with uniform quality and regular shape is at the center of its circle.

summary

1. Definition of gravity:

The force on an object due to the attraction of the earth, symbol G

2. The size of gravity:

The gravitational force on an object is proportional to the mass of the object. That is G=m g

G — Gravity—Newton (N) m—Mass—Kilogram (kg)

g — gravitational constant — 9.8 N/kg

3. Direction of gravity:

straight down

4. The point of action of gravity:

at the center of gravity of the object

Practice questions:

1. Among the following statements about the center of gravity, which one is correct ( )

A. The point where gravity acts on an object is called the center of gravity

B. Only the center of gravity of an object is affected by gravity

C. Center of gravity of a cone with uniform mass distribution

at the midpoint of its axis

D. The center of gravity of a sphere is always at the center of the sphere.

2. Use a spring balance to weigh the small ball hanging at rest below it vertically, then we have ( )

A. The pulling force of the ball on the spring balance is the gravity of the ball

B． The pulling force of the ball on the spring balance is equal to the weight of the ball

C. The object exerting force on the ball by gravity is a spring

D． The object exerting the force of gravity on the small ball is the earth

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Update Time: 2024-11-18

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

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