Holy CRAP. That guy CAN’T report that many significant figures! Since he assumed that the book was 8 inches, then that would mean he could only do one significant figure, thus it rounds down to 1 second. If he assumes the book is 8.5 inches, he can report that as t = 4.25π/10 which, to TWO significant figures, is 1.3 seconds.
Actually he didn’t state the number of significant digits in his 8 inch measurement. I also maintain that he was doing an idealized problem in which both the length and angular velocity were taken to be exact.
Don’t think he had to factor acceleration for such a short distance. Let’s say that we were to insert acceleration.
We would have to know Raquel. Is she of small, medium or large stature and is she right or left handed. So here we go….Let’s say she is petite. 5’2″ approximately 104lbs (47.173kgs for you since you appear to live “down unda”) What force would she exert at the beginning and wind resistance……Wait a sec. Let me do another formula here..OK…
What the fuck is she doing out of the kitchen? The only thing I want to figure out is “How long is it going to take her to fix me a sammich.
But the answer with acceleration would be 1.214333 seconds. This is factoring in my sandwich in her non-dominate hand.
I’m a chemistry major, not a physics major. However, I’m still pretty sure significant figures should be taken into account. His wording of “about eight inches” makes it sound like there is only one significant digit as the only digit is the uncertainty.
ra, it depends. However, physical measurements in experiments are always given in uncertainties. Significant digits are like uncertainties when the uncertainty is assumed to be a power of 10 and the mean is assumed to be a decimal that terminates prior to that power of 10.
However, when you have an equation, the uncertainty propagates differently than the significant digits. The propagation of uncertainty is a complicated process, especially for a nonlinear term like v/d (look it up on wikipedia, as I’m not going to type the whole thing up here).
Suffice it to say that significant digit methods will give you a ‘quick estimate’ of uncertainty, but they’re not adequate for the level of nerdiness and rigor that the post was aiming for. BTW, they’re often used in undergraduate classes anyway to avoid the pain in the ass that comes with propagation of uncertainty.