1. Terminal Velocity

2. Aristotle first recognized that falling objects fall at a constant speed. He probably came to this conclusion based on observations of things falling through water. Falling objects have two forces acting on them. The weight , acting downwards, the frictional drag rushing past, which tries to slow the body down. This drag force acts upwards and therefore lessens the acceleration as the body falls. If the body continues to fall, the acceleration will continue to decrease and at a certain speed, the drag force will just balance the weight, and the body will be falling at a constant rate. This rate is called the terminal velocity.

4. Newton’s Second Law
Terminal Velocity
Finally, the upward air resistance force becomes large enough to balance the downward force of gravity.
This means the net force on the object is zero.
Then the acceleration of the object is also zero, and the object falls with a constant speed called the terminal velocity.
Physical Science

5. Newton’s Second Law
Terminal Velocity
The terminal velocity is the highest speed a falling object will reach.
The terminal velocity depends on the size, shape, and mass of a falling object.
Physical Science

7. Free Fall
Free fall is any motion of a body where gravity is the only or dominant force acting upon it.

8. The faster the object falls, the more air it passes through, so air resistance, or drag, gradually increases.
If the falling object has a large surface area, the force of friction will be greater.
A parachute provides a large surface area.

9. Weightlessness and Free Fall
Formula: D = ½gt²
D = Distance (meters)
g = Acceleration of gravity of a free falling object (m/s²)
t = time (second)
Physical Science

10. Free Falling Objects
It takes a penny dropped off a tall building 6 sec to reach the ground. How tall is this building?
D = Distance (meters)
g = Acceleration of gravity of a free falling object (m/s²)
t = time (second) D =
½ (9.8 m/s²) X (6.0 sec)²
Distance = meters
18 September 2018

11. Free Falling Objects
A daredevil drives his motorcycle off a cliff. If it takes him 5 sec to hit the ground, how tall is the cliff? D =
½ (9.8 m/s²) X (5.0 sec)²
Distance =
122.5 meters
18 September 2018