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

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

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.

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

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

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

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.

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

The mass affects the amount of gravity

The distance between objects affects the amount of gravity

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

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

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