LN: Weight and apparent weight ...

Weight can be a persistent, nagging, problem in physics, as we are finding in this class. Let me say a few words about it.

We defined weight to be mass times gravitational acceleration. One good (or bad?) thing about definitions is that we do not have to think about them!

Now, what is this concept about "apparent weight"? This is the weight that you actually measure. Right here is the confusion... Why do we not say "measure apparent wight" then? We could, and perhaps should, say that, but we usually don't. So, when questions ask "what is the measured weight" that means "apparent weight" not (the true) "weight"!! With this in mind, please review the last problem of Quiz_10-20 ("measured weight") and the first problem of Quiz_10-22 (weight vs. apparent weight).

Here is a related question for you. Suppose you are within a reference frame A (say an elevator accelerating down), which is accelerating relative to an inertial reference frame B (say your laboratory reference frame on a planet), in which the true weight is equal to the apparent weight. Let us say that unfortunately you do not know the gravitational acceleration value (taken to be constant; we are near the surface of the planet) in the frame B (i.e., you do not know which planet you are on!), nor do you know what the acceleration of frame A is relative to frame B. You have lived all your life in frame A. Can you ever figure out your true weight on that planet (i.e., in frame B), not the apparent weight in frame A? If so, how? If not, why?

Leave some comments, if you have brilliant/clever/mundane-but-sincere/just-so-darn-curious ideas, comments, or questions.