Science Terminal Velocity

Free Fall Motion

Because of my latest discovered passion and after a huge research and simplification here is something to keep with my own records about Free Fall, Air Resistance and Terminal Velocity everything really important in skydiving.

Newton's 2nd Law
In physics there's a particular acceleration value so important that it has its own name called the acceleration of gravity and it is represented with the symbol "g". Is this particular acceleration all objects (regardless of their mass) free-fall at 9.8m/s

But why do all objects free-fall at the same rate of acceleration regardless of their mass? Can't be because they all weigh the same! Could it be because they all have the same gravity? or because the air resistance is the same for each object?

Free Fall Motion

Free-fall is a special type of motion in which the only force acting upon an object is gravity. Objects which are said to be undergoing free-fall, are not encountering a significant force of air resistance; they are falling under the sole influence of gravity. Under such conditions, all objects will fall with the same acceleration, regardless of their mass.

As an object falls through air, it usually encounters some degree of air resistance. Air resistance often called "drag" force is the result of collisions of the object's leading surface with air molecules. The actual amount of air resistance encountered by the object is dependent upon a variety of factors but for the purposes of this article only the following two are discussed. The two most common factors which have a effect upon the amount of air resistance are the speed of the object and the cross-sectional area of the object.

Thus:

• Increased speeds result in an increased amount of resistance.
• Increased cross-sectional areas result in an increased amount of air resistance.

Also notice that while rising, both air resistance and weight oppose the object's upward motion. This results in the object losing speed at a rate greater than 9.8 m/sec2 and subsequently, rising to a lower height. On the way down, air resistance increases as the object gains velocity.

Consider this following sequence of images:

When you initially jump, the air resistance force on you is essentially zero and you are in free fall. The net force on you equals your weight and your acceleration equals g (9.8 m/s2).

As you fall your velocity increases. This increased velocity causes the air resistance force on you to increase as well, which causes the net force on you to decrease. Thus as the net force decreases, your acceleration decreases, so you speed up at a slower rate.

At the point where the air resistance force on you equals your weight, the net force on you will be zero, so you will stop accelerating and fall with constant velocity - your terminal velocity.

As an object falls in air:

• its speed increases.
• the air resistance force on it increases.
• the net force on it decreases.
• its acceleration decreases.

until it reaches terminal velocity, where the net force on it and its acceleration are zero. Terminal velocity occurs when the air resistance force equals the weight of the falling object. This means that:

• the object is falling with a constant velocity - its acceleration is zero.
• heavy objects will have a higher terminal velocity than light objects.
  

Since the 150-kg skydiver weighs more (experiences a greater force of gravity), it will accelerate to higher speeds before reaching a terminal velocity. Thus, more massive object fall faster than less massive objects because they are acted upon by a larger force of gravity; for this reason, they accelerate to higher speeds until the air resistance force equals the gravity force.

Again an open parachute increases the cross-sectional area of the falling skydiver and thus increases the amount of air resistance which he encounters. Once the parachute is opened, the air resistance overwhelms the downward force of gravity. The net force and the acceleration on the falling skydiver is upward. An upward net force on a downward falling object would cause that object to slow down. The skydiver thus slows down. As the speed decreases, the amount of air resistance also decreases until once more the skydiver reaches a terminal velocity.