Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: Physics problem --ball rolling down an inclined plane
Replies: 8   Last Post: Dec 26, 2012 10:25 PM

 Messages: [ Previous | Next ]
 Peter Duveen Posts: 163 From: New York Registered: 4/11/12
Re: Physics problem --ball rolling down an inclined plane
Posted: Dec 26, 2012 10:25 PM

Well, Kirby, nice to know people are paying attention to the issue. Regarding the first link,

"If you "race" these objects down the incline, they would definitely not tie! This is because Newton's Second Law for Rotation says that the rotational acceleration of an object equals the net torque on the object divided by its rotational inertia. (Net torque replaces net force, and rotational inertia replaces mass in "regular" Newton's Second Law.)"

My sense in reading Newton's Principia is that he wanted to steer clear of rotational problems. "Newton's Second Law for Rotation" I dare say did not exist. This is one problem with a very common approach to the teaching of mechanics. It is first promised that Newton's laws will explain everything, and then there is a switch and bait, an introduction of new principles, such as torque, etc. that are really not derivable from the first three laws, or at least no derivation is given, if one is indeed possible. In fact, the principle of conservation of energy is also an extraneous principle not included in Newton's tool kit. You don't think this is confusing to students? It certainly got me confused back then.

Date Subject Author
12/20/12 Peter Duveen
12/20/12 Robert Hansen
12/20/12 Louis Talman
12/21/12 Peter Duveen
12/23/12 Robert Hansen
12/24/12 Peter Duveen
12/24/12 Robert Hansen
12/25/12 kirby urner
12/26/12 Peter Duveen