Newton's First Law for Dummies

Acceleration effects on driver

Some of our most fascinating freelancer foul-ups arise from wannabes who are (or at least claim to be) studying science at the college level. Apparently, they are convinced that they know it all... the problem being, of course, that they don't. Some of them, we've determined, not only don't know it all, they don't know any of it. Or, at least, they can't put what they know into words that make sense. Take, for example, Hubbie Dani Alicia, and her HubPages.com post, "Newton's Three Laws of Motion and How to Use Them."

Dani (real name Danielle Clemons) wrote this when a student supposedly with a double major in physics and theater (she's now a Mary Kay agent). We suspect the reason she didn't go farther in physics is exemplified by her notion of Newton's principles. Take, for instance, her example to explain Newton's first law:

"This can be demonstrated by watching a bug in a car. If you've ever been unfortunate enough to have a fly in your car while your driving, you may have noticed that even though the car is going forward, the fly is buzzing around in the car as if the car wasn't moving. That's because although the car has a force exerted on it, the fly does not. If the fly were to land on a seat (ewww!) then it would take on the velocity of the car, and the friction between the fly's legs and the car seat would then propel the fly forward."

No, Dani: the fly is contained in the volume of air within the moving car, which is itself moving because it's contained within the car. No matter what the fly does inside a car moving at constant velocity, it shares the car's momentum until it leaves through a window. The way Clemmons wrote her example, it appears that the fly powers its forward motion until it lights, which is bull. The real illustration of Newton's first law is that a loose object in the vehicle – for example, a fly in the air or a golf ball on the floor – would move backward on acceleration, forward on deceleration, and to the side with a change of direction.

Next, Dani displays her ignorance of space:

"If Superman flew into space and were to throw a rock, the rock would continue to move in the direction that Superman threw it and at the same speed that he threw it because there is no gravity in space. Since there is no gravity, there is nothing to stop the rock so it will continue it's [sic] path until it crashes into a meteor or enters the gravitational pull of a planet or moon."

We hate to tell her this, but there is indeed gravity in space. Gravity is a function of mass and proximity to it, not the presence or absence of air. What Dani should have said is that there is (little or) no friction, so the rock wouldn't decelerate.
Dani's explanation of Newton's second and third laws are generally on-target, although she really should learn that (on Earth, anyway) the force of gravity is generally in the z direction, not y. Sadly, the mess our Dumbass of the Day made by trying to use a "real-world" example for Newton's first law pretty much ruined subsequent efforts.

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