# Newtons Fourth Law Universal Gravitation U Universal nive

• Slides: 9

Newton’s Fourth Law Universal Gravitation U Universal nive rsal Gravitation U nive rsal

What is Gravity? • Attractive force between two objects with mass • Strength of attraction depends on: – Mass of each object (in kilograms) – Distance between the objects (in meters) – Gravitational Constant (G = 6. 67 x 10 -11 N∙m 2/kg 2)

Gravitational Proportions The force of gravity is DIRECTLY proportional to the masses of the objects attracted to one another If If thethe mass ofof BOTH one objects is doubled, the force of gravity is…

Gravitational Proportions The force of gravity is INVERSELY proportional to the SQUARE of the distance between the objects attracted to one another If If the distance between the objects isis doubled, tripled, the force of gravity is…

So what does the gravity from the Moon affect here on Earth? • Tides – Water on earth is attracted by the moon’s gravity and will create a bulge on the earth Bay of Fundy off the east coast of Maine

Examples • What happens to Fg in the following cases? onedouble mass the distance -Double one-Double mass and Double the distance 2 X 2 x ¼x ½x ¼ X masses Double both -Double both-Triple massesthe and double the distance 4 X distance 4 x-Triple 1/9 ¼ x 1 x X one mass -Halve one mass the and halve the distance -Halve 3 X distance 4 X 4 x ½-Triple x 2 x both masses the distance 9 X Triple one-Quarter mass and quarter the distance one 3 x -Halve 16 X 16 mass x 48 x ½X -Halve one mass and double the other 1 X

30 0 4 x 105 kg 0 m 6 x 105 kg Fg = 1. 78 x 10 -6 N

Gravitational Fields • Objects with MASS produce gravitational fields • Field lines point inward from ALL DIRECTIONS

• Find the Force of Gravity between you and the person sitting next to you