Science Ch. 5 Lesson 4

1. Science Ch. 5 Lesson 4 • By Grace O’Doherty

2. Gravity: A Force of Attraction • a force of attraction between two objects that is due to their masses is called gravity

3. All Matter is Affected by Gravity • all matter has mass and gravity is a result of mass (therefore, all matter experiences gravity) • this gravitational force “pulls” objects towards one another • you don’t see this force of attraction because the mass of most objects is too small

4. Earth’s Gravitational Force is Large • compared to most objects around you, the Earth has an enormous mass which means it also has an immense gravitational pull • Earth’s gravitational force pulls everything toward the center of the Earth

5. The Law of Universal Gravitation • a British scientist named Newton whose work on forces and light was very important in the vast development of science • it is believed that Newton made a huge connection when he saw an apple fall from a tree • he concluded that there had to be an unbalanced force on the apple in order to make it fall and that that certain force was called gravity • Newton generalized his observations on gravity in a law now known as the law of universal gravitation • this law describes the relationships between gravitational force, mass, and distance

6. The Law of Universal Gravitation • this law firmly states that all objects of the universe attract each other through gravitational force • the law of universal gravitation can also be expressed mathematically: • F = G X (M1 X M2) Over R(squared) where G = 6.673 X 10 (to the negative eleventh) and N X M(squared) over kg(squared)

7. Part 1: Gravitational Force Increases as Mass Increases • the moon has less mass than Earth, therefore, the moon’s gravitational force is less than that of the Earth

8. Part 2: Gravitational Force Decreases as Distance Increases • the gravitational pull between you and the Earth is large while you have a weak gravitational pull towards the sun • the reason for this is because of distance (you are close to Earth but far away from the sun)

9. Weight Is a Measure of Gravitational Force • the measure of the gravitational force exerted on an object is called weight • weight is expressed in newtons (N)

10. Weight and Mass Are Different • weight changes when gravitational force changes while the value of mass never changes • gravitational force is about the same everywhere on Earth, so the weight of any object is about the same