1. Don’t let it get you down!
Gravity
Don’t let it get you down!

2. Essential Questions Define gravity
Explain the law of universal gravitation

3. Aristotle Ancient Greece around 400 BC
He believed that the heavier the object, the faster it falls.

4. Galileo Galilei The Leaning Tower of Pisa
In the late 1500s, an Italian scientist named Galileo Galilei decided to prove Aristotle wrong.
Galileo theorized that all objects will land at the same time when they are dropped from the same height.
The Leaning Tower of Pisa

5. What is gravity?
Galileo helped us understand gravity as a force that exists between the Earth and objects.
Newton showed that the same force exists between all objects.
Even today, no one knows exactly
why objects attract each other.

6. The Law of Universal Gravitation
The size of the gravitational force depends on two things:
Mass of the objects
Distance between the objects

7. What is weight?
Weight is a measure of the gravitational force exerted on an object.
weight is expressed in newtons (N)

8. Elephants & feathers
Objects fall to the ground at the same rate because acceleration due to gravity is the same for all objects.

9. Air Resistance
The amount of air resistance depends on the size and shape of an object.
While gravity pulls an object down towards the center of the Earth, the air resistance pushes an object up from the Earth.

10. Gravity & Acceleration
Objects accelerate towards Earth at
9.8 m/s2.
It is the same for all objects, regardless of their mass.
Notice, the ball isn’t traveling at 9.8m/s2, it’s accelerating at 9.8 m/s2.
It’s velocity is continually increasing.
Only the acceleration remains constant.
Each picture was taken 1 second apart, but notice how the ball travels a greater distance between each second.

11. Free Fall When there is no air resistance, an object is in free fall.
An object is in free fall only if gravity is pulling it down and no other forces are acting on it.