1. Gravity Notes Part 1

2. What is a Gravity? First described by Isaac Newton
Observed an apple fall from a tree straight to the ground
Concluded an invisible force was pulling the apple toward Earth

3. What is a Gravity?
Gravity = a force that pulls objects toward one another
All objects exert a gravitational pull on one another
The one we experience the most is Earth’s gravitational pull

4. When you hold a book in the air it does not fall Gravity pulls down
What is a Free Fall?
When you hold a book in the air it does not fall
Gravity pulls down
Your hand pushes up
Net force = 0N = no movement
Hand = 50N
Gravity = 50N

5. Net force = 50N down = movement down
What is a Free Fall?
When you let go it falls
Gravity pulls down
No other force acts
Net force = 50N down = movement down
Gravity = 50N

6. What is a Free Fall?
Free fall = when gravity is the only force acting on an object
This causes objects to accelerate downward
Acceleration due to gravity = 9.8m/s2

7. What is a Free Fall?
Example: It takes 5 seconds for a book to fall to the floor. If acceleration due to gravity is 9.8m/s2, what speed did the book reach before hitting the ground?
S=A(T) = 9.8m/s2 (5s) = 49m/s S A T

8. What is a Free Fall?
All objects, regardless of size or mass, fall at the same acceleration rate.

9. What is a Free Fall?
All objects, regardless of size or mass, fall at the same acceleration rate.

10. Feather and Hammer Drop
Which would hit the ground first?
Why?
Hammer vs. Feather
Feather and Ball bearing

11. Table
Small Ball Average
Large Ball Average A B C D E F

12. In real life, some objects fall faster than others.
Air resistance
In real life, some objects fall faster than others.
Ex: A basketball falls faster than a leaf.
5 seconds
Gravity = 10N
2 seconds

13. This is due to air resistance Fluid friction against the object
Some objects are more aerodynamic than others.
Air Resistance
Gravity

14. If air resistance becomes great enough, it equals the force of gravity
This results in balanced forces
Acceleration stops
The objects stays at a constant speed = terminal velocity
Air resistance =100N
Gravity pull=100N

15. Any Questions?