"Gravity" Force and Motion PPT Courseware 2

Description

"Gravity" Force and Motion PPT Courseware 2

1. Gravity

Between any two objects in the universe, from as large as celestial bodies to as small as dust, there is a force of mutual attraction, that is, universal gravitation.

Gravity: The force exerted on an object due to the attraction of the earth is called gravity.

1. Symbol: G

2. Unit: N

Notice:

(1) All objects near the ground are affected by gravity;

(2) The object exerting force by gravity is the earth; the object receiving force is the object of study

(3) Gravity is part of the universal gravitation.

(4) Gravity is related to the mass of the object and its geographical location

2. Direction of gravity

The direction of free fall of an object from rest

The direction of the suspension line when the object is suspended and at rest

Explore the relationship between the gravity and mass that affects an object

The greater the mass of an object, the more ______ the gravitational force it may experience. (size)

Explore the relationship between gravity and mass

1. What tool is used to measure gravity?

How to measure the magnitude of gravity?

Hang a hook code of known mass on a spring dynamometer. When stationary, the indication of the spring dynamometer is equal to the gravity on the hook code.

2. Increase the hook numbers one by one, measure the gravity they bear, and record them in the table.

The gravitational force on an object is proportional to its mass

G/m=g i.e.: G=mg

Among them g=9.8N/kg

The meaning is: an object with a mass of 1kg near the ground experiences a gravity of 9.8N

Example 1: A student’s body mass is 50kg. What is the gravity he experiences?

Solution:G=mg=50kgx9.8N/kg=490N

Example 2 The mass of an elephant is 4.5 tons. What is the pressure it exerts on the ground when it stands on the ground? (g=10N/kg)

Solution: m=4.5 tons=4500kg

G=mg=4500kgx10N/kg=45000N

F=G=45000N

Answer: The pressure the elephant exerts on the ground is 45000N

Consolidate and improve:

1. Gravity: The force exerted on an object due to ____________ is called gravity

2. The magnitude of gravity is related to the mass of the object _____, G=_____.

Gravity is represented by _____, the unit is _____, mass is represented by _____,

The unit is _____, the meaning of g=9.8N/kg is: _______________________.

3.The direction of gravity _____.

4. Center of gravity: The __________ of gravity is called the center of gravity. The center of gravity of an object with uniform mass distribution and regular shape is on its __________.

2. The athlete kicks the football from the backcourt to the frontcourt. When the football moves in the air, regardless of the air resistance, the force it receives is ( )

A. Only the force of the kick

B． only affected by gravity

C. Kick force and gravity

D． not affected by force

3. The picture below shows a shot put flying in the air. Please draw a schematic diagram of the gravity on the ball.

4. Draw a schematic diagram of the gravity on the ball on the inclined surface as shown in Figure 2.

5. The static ball in the picture weighs 10N. Please use a schematic diagram of force to draw the gravity on the ball and the pulling force of the rope on the ball.

Because the ball remains stationary, the pulling force F and gravity are balanced,

So:F=G=10N

6. The moon also has a gravitational force on objects on its surface, and this gravitational force is 1/6 of the earth. A person who can move an object weighing 600N on the earth can move () on the moon.

A. Objects heavier than 600N

B. Objects weighing less than 600N

C. An object weighing 600N

D. Unable to determine

7. If there was no gravity, which of the following phenomena would not occur ( )

A. There would be no such proverb as "people go to higher places, and water flows to lower places"

B. The glass will not break if thrown to the ground

C. Traditional sports competitions have lost their meaning.

D. "Climbing to the sky" is no longer a difficult task

8. Which of the following statements about gravity is incorrect ( )

A. All objects on the earth are affected by gravity

B. Gravity does not require the earth and objects to be in contact with each other

C. The failure of the toy "tumbler" to fall is the result of gravity.

D. Tightrope walkers hold a long pole in their hands for a more exciting performance.

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For more information about the "Gravity Force and Motion" PPT courseware, please click the Gravity ppt Force and Motion ppt tag.

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Update Time: 2024-10-25

This template belongs to Physics courseware Lu Jiao Edition Eighth Grade Physics Volume 2 industry PPT template

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