Thanks for the validation, Brad. Each instructor has their own methods because this was indeed the first example presented to me when I took physics years ago to make the distinction between speed and velocity. The professor said straight up it would be the very first question on the exam (it was) and anybody who got the question wrong would fail the exam. Nobody failed, to my knowledge. It wasn't treated as a trick question, it was fundamental material.
He often reused examples across different topics so we could focus on the relevant new information and cut down the noise/relearning. For example, the running track was reused (with slight modifications) as an introduction to 'work' illustrating no work is performed if there is no displacement. Since he already proved the theory with velocity, he didn't have to waste time re-explaining it for work. While tough at first due to the abstract nature, I found his approach very refreshing as it allowed me to tackle tougher problems because I was exposed to the edge cases upfront and conditioned to not think of them as edge cases. Edge cases are a product of our tools (math) to explain observed behavior. The universe doesn't have a concept of edge case. I think my professor chose this approach because he once mentioned students had problems progressing from newton's laws to quantum mechanics because as they entered more advanced levels, they tended to forget previously learned material still applied (or they didn't see the connection). He conditioned students to think more about the problem rather than merely choose a formula and plug in numbers. Often his toughest problems required the least amount of math to solve. Some of his lectures could be really dry, as he was a dry guy himself, but he was probably the best physics professor I had of many. Matt From: [email protected] [mailto:[email protected]] On Behalf Of Bradley Gabe Sent: Thursday, February 14, 2013 1:21 PM To: [email protected] Subject: Re: Difference between a force and a velocity ? In the past 2 years, I attended college courses in Physics 101 and 201 at UT Dallas, as well as a Princeton Review course for the MCAT's which include heavy study in basic physics, especially about the definitions of fundamental units and concepts. As it turns out, Matt is correct in that the example of displacement returning to origin will result in an average velocity of 0. Both my physics professor as well as the Princeton Review instructor took special care to mention this specific example more than once because it is a common trick question on the MCATs. HOWEVER, and this is important. It is absolutely NOT the first and only example provided to explain the difference between velocity and speed. Nor did it come up during the first lecture about velocity. It was brought up long after we had repeatedly reviewed the concept, in an attempt to trip us up in order to demonstrate the exception. Defining velocity and then using zero displacement to explain it is similar to introducing the letter 'p' and using the word 'pneumonia' as your very first example. If you have a problem with that, take it up with the lexicographers and wordsmiths? -B
