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# 8.2: Free Fall

## Skydiving Free Fall

The time a skydiver spends between leaving the aircraft and opening a parachute is often called the “free fall” time. During a recreational skydive the “free fall” time is about one minute. The current record “free fall” time of about 5 minutes was set by Alan Eustace in 2014 when he fell from an altitude of more than 135,000 feet. According to the Paragon Space Development Corporation, “Eustace reached top speeds of over 800 miles per hour. He was going so fast that his body broke the sound barrier, creating a sonic boom that could be heard on the ground.” The jump broke the previous record of 127,852 feet set by Felix Baumgartner in 2012. The 2012 jump was sponsored by GoPro cameras and the video has a much higher production value than the more recent 2014 jump:

October 14, 2012, Felix Baumgartner ascended more than 24 miles above Earth's surface to the edge of space in a stratospheric balloon. Millions across the globe watched as he opened the door of the capsule, stepped off the platform, and broke the speed of sound while free falling safely back to Earth. Felix set three world records that day—and inspired us all to reach beyond the limits of our own realities, and reimagine our potential to achieve the incredible.

## Physics Free Fall

Now that we have introduced the skydiver’s use of the term free fall, we need to recognize that physics uses the term free fall in a completely different way, so we will need to be careful to avoid confusion. In physics, and in this book, we use the term free fall to describe the motion of an object when gravity is the ONLY force acting on the object. Skydivers experience gravity and air resistance, so technically they are not in free fall.

1. "Skydive Miami" by By Norcal21jg, from Wikimedia Commons is in the Public Domain