Chapter 4 Gravitational Forces

Forces acting through fields Here's one example of a force acting through a field over a distance without touching . Question**Is the red ball affected by Earth? What force is at work in this diagram Yes, Gravity

Newton's Universal Law of Gravitation Any two objects with mass will exert a force of attraction to each other even over vast distances. This force acts on both objects, pulling them towards each other. Gravity -has traditionally been defined as a force of attraction between things that have mass. SO…2 factors that affect the force gravity are : Mass and Distance

Comparing forces of gravity Compare the force of gravity acting on you 
(your weight) on Earth compared to the moon Question: Which is larger? Why? *WE TALKED ABOUT THIS ALREADY!

Comparing forces of gravity What happens to the force of gravity on an object as we move farther away from a massive object like Earth? A B C

Distance and forces of gravity The force of gravity exerted by an object decreases as it moves away from an object like Earth. So, the boy at C will have the smallest gravitational pull on the Earth.

What about mass? Even though there is always a gravitational force acting between masses, it is only noticeable when the objects' masses are relatively large. So Small Masses = Small Force of Gravitation Large Masses = Large Force of Gravitation

Important Diagram

Lets apply The Sun is a massive star in the solar system. Question** As the planets move away from the Sun what happens to their gravitational force? Even though the moon has less mass than the Earth, its distance is close to us, so its gravitational pull can effect our planet ( its strong ) The concept of gravity will be important when we do Astronomy in Marking Period 3

Concept Check What did we learn so far?

12 The force of gravity _________ as the 
object's mass increases. [This object is a pull tab] Answer A A Increases B Remains Constant C Decreases Answer : A

13 The force of gravity _________ as the 
distance between two objects increases. [This object is a pull tab] Answer C A Increases B Remains Constant C Decreases Answer - C

4 What happens to the force of gravity between two objects as they move apart? [This object is a pull tab] Answer B A Increases due to distance B Decreases due to distance C Nothing because the masses dont change D impossible to tell without knowing what the objects are Answer - B