Hurtling towards earth at 200 km/h with nothing more than a bunch of nylon and strings packed into a rig on your back is truly exhilarating! The sound of the rushing wind takes over your auditory senses and gravity fiercely tugs at your body while the air molecules are desperately trying to slow you down. You relax, yet your limbs do not fall as they are held up by the wind pressure. Using your arms and legs as rudders you can turn, fly forwards and if you're not careful become unstable in a hurry. After less than ten seconds you've hit terminal velocity. It's absolutely thrilling. It's also addictive. I check my altimeter, it reads 5000 feet; still another 1000 feet of freefall before I pull the ripcord.
I've done eight jumps in the past two days and progressed a fair amount on my free fall program. The first jump back was, well, interesting. I hadn't jumped for over a month and managed to build up a fair amount of anxiety on the plane ride up to altitude. I was pretty confident that I remembered the basics. Arch. Count. Pull something. Preferably your ripcord. I exited the plane and flipped onto my back. Seeing the sky above, I knew this was not a good position to deploy. Hard arch, thrusting out my pelvis and looking up and voila, I flipped back onto my stomach. It's amazing, thrust your pelvis back and forth and the rushing wind flips you from your stomach to your back like a pancake.
On my last jump of the day, I was to dive out of the plane head first, like into a swimming pool. The key was to remain stable and not flip over on the exit; with correct body position, this would be achievable. I slid open the rolling plexi-glass door and got into a crouching position. I looked at my jump master and he gives me the go signal. I dive out towards the back and feel the rushing wind push my body into a vertical position; I'm doing a headstand in the air! I kick up my legs and my body levels out. A perfect exit. A few thousand feet later, it was time to pull and as I had been playing around I wasn't completely stable. As I reach for the ripcord, I must have dropped my shoulder too much and consequently started flipping over into a spin. The parachute deployed and whipped me around like a rag doll. I thought my legs had been ripped clear off. The risers were twisted down into the back of my neck and I couldn't even look up to see if my canopy was open. The rush of the wind stopped and according to the alti I wasn't plummeting to earth. This was good. I gently kicked myself out of the twists and luckily had a fully functioning canopy. The flight back down was also quite interesting as I had to fly through thick clouds. Looking at the clouds from the ground, they deceivingly look like these soft fluffy cotton balls. Flying through a cloud is a different story. A turbulent, cold and moist white-out condition in which you temporarily lose all spatial sense bares little resemblance to fluffy cotton balls. Once through the clouds, I managed to land on target in the circle.
Thanks to everyone at Ground Rush Adventures; you guys are great! Hope to be back there again soon!
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Terminal velocity of a falling body occurs during free fall when a falling body experiences zero acceleration. The body will experiences zero acceleration because of the retarding force known as air resistance. Air resistance exists because air molecules collide into a falling body creating an upward force opposite gravity. This upward force will eventually balance the falling body's weight. It will continue to fall at constant velocity known as the terminal velocity.
The magnitude of terminal velocity does vary and depends on the weight of the falling body. For a heavy object, the terminal velocity is generally greater than for a light object. This is because air resistance is proportional to the falling body's velocity squared. For an object to experience terminal velocity, air resistance must balance weight. An example that shows this phenomenon was the classic illustration of a rock and a feather being dropped simultaneously. In a vacuum with zero air resistance, these two objects will experience the same acceleration. On the earth however, this is not true. Air resistance will equal weight more quickly for the feather than it would for the rock. Thus the rock would accelerate longer and experience a terminal velocity greater than the feather.
Another factor that affects terminal velocity is the orientation at which a body falls. If an object falls with a larger surface area perpendicular to the direction of motion it will experience a greater force and a smaller terminal velocity. On the other hand, if the object fell with a smaller surface area perpendicular to the direction of motion, it will experience a smaller force and a greater terminal velocity. The terminal velocity for a skydiver was found to be in a range from 53 m/s to 76 m/s (190 km/h to 273 km/h). The value is variable since the weight and the orientation of the falling body play significant roles in determining terminal velocity.