Physical Science Mr. Barry

Gravity is a Force  Every object in the Universe exerts a force on every other object  Gravity: force of attraction between two objects  Often this force is too slight to notice  Can you feel the person next to you pulling on you?

Discovery of Gravity  First discovered by Sir Isaac Newton  Included in his 3 Laws of Motion (to be covered later)  Did he really discover it or was it already there?

Calculating Gravity  Gravity depends on:  1. The mass of the objects attracted to each other  2. The distance between the two objects  Because everything here on Earth is much smaller than the Earth and is relatively close to the Earth, gravity is considered a constant  g = 9.81 m/ s 2

Calculating Force of Gravity  Your “force of gravity” is more commonly known as your weight  W = mg  W = weight (Newtons)  m = mass (kg)  g = gravity constant ( 9.81 m/s 2, always the same on Earth)  Add this to your equation sheet!!  This is why weight and mass are not the same thing!!

Gravity = Constant  Everything, no matter how massive, has the same gravitational acceleration  If the only force on two objects is gravity, they will fall at the same rate  Famously discovered by Galileo at the Leaning Tower of Pisa

Vertical Motion  Objects accelerate downward because of gravitational force  “Free Fall”  This means their speed increases the longer they fall