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# Parachute

## What kind of experiment is this? ## Experimental procedure and explanation:

• Parachutes are made to increase air resistance and reduce the speed of fall. Let’s verify this.
• In this experiment, a plastic sheet is cut into a hexagon with each side equal to 40 cm. Each corner is tied to a 50-cm long thread.
• A tennis ball is dropped from a height of 20.4 m. The time for the ball to reach the ground is measured to be about 2.0 s; this is approximately the same as the time required if air resistance is ignored (2.04 s).
• When a parachute is used, the time to reach the ground increases to about 9.7 s.
• In the initial phase of the descent, the speed increases, but due to air resistance, the object falls at a constant speed after a certain point. At this time, the air resistance could be considered to be equal to the gravitational force and the terminal velocity is reached.
• The terminal velocity depends on the size (in this experiment, the area of the parachute), shape, and mass (the lighter the object, the lower the terminal velocity) of the object. However, the speed cannot exceed the terminal velocity, regardless of the height from which the object is dropped. For example, the terminal velocity remains the same irrespective of whether the object is dropped from an altitude of 500 m or from 3000 m. The purpose of using the parachute is to reduce speed during the fall, but it is important to note that that the terminal velocity cannot be exceeded.
 [Keywords] Air resistance, Terminal velocity [Related items] Raindrop, Heavy Ball and Light Ball, Large Ball and Small Ball [Reference] “Illustrated Fluid Dynamics Trivia,” by Ryozo Ishiwata, Natsume Publishing, pp. 78–79.
Last Update：1.21.2015