 # Gravity & Free Fall.

## Presentation on theme: "Gravity & Free Fall."— Presentation transcript:

Gravity & Free Fall

Elephant vs. Feather If both are dropped from the same height at the same time, which will hit the ground first? On Earth? On the moon?

Freefall Movement of an object towards earth solely because of gravity
Gravity acts downwards towards center of earth Acceleration due to gravity for any falling object = g g= 9.8 m/s2

What “g” means Any object in free fall will increase its speed/velocity by 9.8 m/s each second. g (9.8 m/s2) stays constant for the duration of free fall

Ball in free fall Time = 0 s v = 0 Time = 1 s v = 9.8 m/s
The change in ball’s speed is always 9.8 m/s2 Time = 2 s v = 19.6 m/s ball is covering more distance the longer it falls Time = 3 s v= 29.4 m/s

Viewing Free Fall Free Fall applet

Air Resistance Present on earth acts in opposite direction of gravity
(reduces acceleration) Falling Ball Gravity g=9.8m/s2 Air resistance

Air Resistance If objects fall for long period of time:
Force of Air resistance = force of gravity Forces balanced Object falls at constant speed called terminal velocity

Terminal Velocity Air resistance increases with: 1. Increasing Speed
2. Increasing surface area Parachutes slow downward acceleration

Viewing Terminal Velocity

Elephant vs. Feather Without air resistance (outer space)
Free falling objects Both hit at same time

Elephant vs. Feather With air resistance (earth) With air resistance
Elephant hits first