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G = acceleration of gravity on earth = 32.2 ft per second per second. It can also be expressed in metric units as 9.8 m/s/s. This is not purely a constant for the entire planet, but varies based on the density of rocks in the earth’s crust in each specific area. The gravitational attraction between any two bodies is related to the mass of each of those bodies. Do you realize that, since you have measurable mass, you are actually pulling the earth toward you slightly by YOUR OWN GRAVITATIONAL FIELD?
Velocities in macrophysics are generally identified as linear or angular. An example of linear velocity would be miles per hour. Generally we consider linear velocity as a vector in that it has associated both a magnitude and a direction. Angular velocities involve rotation in a direction (around a center point), and an example could be degrees/sec. how does this work? Think about the sweeping second hand on a clock. Since it goes all the way around once in a minute, you could say that its angular velocity is 360 deg/60seconds or 6 deg/s. This is a constant angular velocity (unless you’ve got a problem with your clock J).
So when velocities change (either increasing or decreasing), we say that the object is accelerating. Some people argue whether something that is slowing down is “decelerating”, or experiencing “negative acceleration”. I don’t really care, it’s not hard to understand either word. So what happens when the object has some linear components and some rotational components to its travel? It moves in a curve. Like our rod tip.
Regarding whether the rod tip experiences constant or increasing acceleration -- I have not seen, heard, or read of any definitive study. The stuff I did in AK, I believed that I was seeing an amazingly constant linear acceleration of the rod tip when the rod maintained load properly (i.e. – retained SLP). I traced the tip positions at every 40th of a second (I think that’s the sample rate that I used) and measured between those points to determine instantaneous velocities. >From the instantaneous velocities, I calculated the acceleration between the frames. Wish that I could find those books, or even the tapes so I could go back and redo my analysis. I really felt enlightened at the time, but now it’s a bit foggy…
Regards -- TAM -----Original Message-----
More on acceleration. |