1. “A force of attraction”
Section 1-4: Gravity
“A force of attraction”

2. The Effects of Gravity on Matter
Gravity is a force of attraction between objects due to their masses
Gravity can change the motion of an object by changing its speed, direction, or both

3. The Effects of Gravity on Matter
All matter has mass and gravity is a result of mass
All objects experience an attraction toward other objects
The mass of most objects is too small to cause a force large enough to move objects toward each other.

4. The Effects of Gravity on Matter
Compared to objects around you, the Earth has a huge mass
Therefore, Earth’s gravitational force is very large
Earth’s gravitational force pulls everything toward the center of Earth

5. Newton and the study of gravity
In 1665, Newton tries to explain 2 puzzling questions
Unbalanced forces are needed to change the motion of objects
Proposed that 1 force, gravity could do this

6. Law of Universal Gravitation
A summary of Newton’s ideas about gravity
Law that describes the relationships between force, mass, and distance
This law applies to all objects in the universe

7. The Law of Universal Gravitation
All objects in the universe attract each other through gravitational force.
The size of the force depends on the masses of the objects and the distance between the objects.

8. The Law of Universal Gravitation
Gravitational force increases as mass increases
The moon has less mass than Earth, therefore, the gravitational force is less than Earth’s
Gravitational force decreases as distance increases

9. The mass affects the amount of gravity

10. The distance between objects affects the amount of gravity

11. The difference between weight and mass
Weight is a measure of gravitational force on an object
Usually refers to the Earth’s gravitational force on an object
Weight changes when the gravitational force changes

12. The difference between weight and mass
Mass is the amount of matter in an object
Mass of an object does not change

13. Units of Weight and Mass
Weight is measured in Newtons (N)
Can be measured with a scale
Mass is measured in kilograms (kg)
Mass is measured using a balance