Parachutes for Dummies

Few freelancers are more likely to irritate our staffers than the liberal arts majors who take on technical topics and make a complete mess out of them. We run across so many of them that they even have their own tag on our blog.  Well to the hundreds of entries under that tag, we're here to add yet one more. We'd like to welcome back Shaunta Alburger, owner of several liberal arts degrees, and her attempt to explain "The Physical Factors Affecting Parachutes."

Alburger nibbled around the edges of the question, but she never actually got to the answer. Instead of discussing the surface area and shape of the parachute, its mass and that of the payload, and the ambient air pressure; Shaunta attempted to describe gravity, air resistance, and terminal velocity. Her problem was, unfortunately, that she didn't understand any of the topics she brought up. Here are a few of her more... "cogent" observations.

• "A parachute is a length of light-weight fabric attached to a heavier object..." – We'd probably speak of the fabric's "area" instead of its "length."
• "Parachutes reduce gravity to the point that a human body can safely fall from an airplane while using one." – No, Shaunta, a parachute does not "reduce gravity"!
• "This is air resistance. Air collects under the fabric parachute, pushing it up as gravity pulls the heavy object attached to it down. " – No, air resistance does not "push up." You seem to be trying to explain drag, but you're screwing up.
• "Terminal Velocity... Opening a parachute changes terminal velocity, making it much slower than the terminal velocity of an object in free fall. The open parachute results in air resistance that is greater than the pull of gravity. Terminal velocity reduces until there is a balance again, which happens at a speed slow enough for the falling object to make a safe landing." – Well, yeah, sorta. We're pretty sure air resistance doesn't exceed the force of gravity, at least not on Earth. As for that "Terminal velocity reduces until there is a balance again" bullshit, well, it's bullshit.

As we said before, Alburger nibbled around the edges of the actual answer, but had too little scientific knowledge to get it right. A parachute changes terminal velocity of an object by (greatly) increasing its surface area to mass ratio. All Shaunta had to do was say that somehow.

She didn't say that (or anything remotely similar to it); never even using the word "drag," which is the name for the force that opposes gravity in the physics of parachutes. Hence, her award for being the Dumbass of the Day.

SI - PHYSICS