1. Law of Gravitation

2. Law of Gravity  Gravitational Force  All objects have mass and therefore will attract all other objects.  The size of the gravitational attraction or force depends on  The mass of both objects  The distance between the two objects  Equation: F g = Gm 1 m 2 r 2 G = gravitational constant = 6.67x10 -11 Nm 2 /kg 2 m 1 & m 2 = mass of objects r = distance between the center of objects

3. Example: Find the gravitational force between you and the earth.  Mass of earth = 5.98x10 24 kg  Radius of earth = 6.37x10 6 m

4.  How does mass affect the force of gravity  (direct relationship)  If the mass goes up, the force goes up  If the mass goes down, the force goes down  Example: F g = Gm 1 m 2 r 2

5. Inverse Square Law  How does distance effect the force of gravity  Inverse Relationship  If the distance increase, then the force decreases  If the distance decreases, then the force increases  However, YOU NEED to square the number to get the overall affect What is the relationship between F g and r? F g = Gm 1 m 2 r 2

6. Weight  The common name we use to describe the gravitational force between an object and the earth.  Symbol: FgFg  Equation:  F g = m x g  m= mass of the object  g = acceleration due to gravity (-9.8 m/s 2 )

7.  Weight and mass are not the same;  mass = amount of matter  Measure in (kg)  weight = the amount of pull between you and the earth  Measured in ( Newtons (N) or Pounds (lbs) )  Example: Find your weight

8. Let’s set the 2 equations equal to each other since they BOTH represent your weight or force due to gravity SOLVE FOR g! Acceleration of Gravity