1. Chapter 3 Section 3 Mrs. Faria
Free Fall
Chapter 3 Section 3
Mrs. Faria

2. Galileo’s Experiment
Galileo dropped several objects with different weight and from different heights
He concluded that when air resistance is neglected, all objects in free fall had the same acceleration

3. Acceleration Due to Gravity
The acceleration of an object in free fall that results from the influence of Earth’s gravity.
Gravity = 9.8 m/s2
Comes from the center of the Earth
Differs from planet to planet

4. Acceleration Due to Gravity

5. Acceleration Due to Gravity
g = -9.8 m/s2
Max Height
Velocity is ZERO
Acceleration = -9.8 m/s2
Way Up
Velocity is decreasing
Speed is decreasing
SLOWER
Acceleration = -9.8 m/s2
Way Down
Velocity is decreasing
Speed is increasing
FASTER
Acceleration = -9.8 m/s2

6. Maximum Height
What is the velocity of the ball at the top of its flight?
0 m/s
What is the acceleration of the ball at the top of its flight?
-9.8 m/s2
What would happen if the both velocity and acceleration are zero at the top of the ball’s flight?
The ball would float.

7. Acceleration Due to Gravity
g = -9.8 m/s2
Velocity (m/s)
Way Down
Velocity is decreasing
Speed is increasing
FASTER
Acceleration = -9.8 m/s2
DROP
When an object is dropped, the initial velocity is zero.

8. Kinematics Equations ∆x becomes ∆y a becomes g vf = vi + at
Kinematics in the X
Kinematics in the Y (FREE FALL)
vf = vi + at
vfy = viy + gt
∆x = vit + ½ at2
∆y = viyt + ½ gt2
vf2 = vi2 + 2a∆x
vfy2 = viy2 + 2g∆y

9. Problem Solving (Points to Remember)
Acceleration is always -9.8 m/s2
At maximum height
Velocity is zero
Acceleration is -9.8 m/s2
Always let your starting position be zero (up=+ & down = -)
When an object is dropped, initial velocity is zero
When an object is thrown into the air, it must have an initial velocity
Time up is equal to time down
At any given point, velocity up is equal to velocity down.
If the object lands below the starting position, then ∆y is negative.
Velocity going up is always positive, velocity going down is always negative.