Quote:
David Skaggs wrote:
I see that we need a common starting point that everyone ( there will always be at least one who won't) can agree on. To keep it simple, I suggest the first 38 seconds of the following link as that starting point. This describes what is going on outside the body ( the body being the orange block in the video) .
http://www.youtube.com/watch?v=pNG8CAmszH0
The question is what is going on inside the body to redirect the force(s) applied outside the body to the ground without the body collapsing?
David
|
OK, the zombie master revives me. Beware.
First. The diagram is NOT doing what we are doing to the block (if it were another person). The model shown is a translation (against sliding friction) without rotation --whereas what we are (usually) doing is fundamentally a rotation (every several different types and cycles) but rotations nonetheless. How do you move a refrigerator single-handedly?
Vectors are harder in many respects because they involve an abstract force with an acceleration term, and are hard to "see" when acting in more than one plane. Moment just involves distance and mass, and rotations from one plane to another are relatively easy to "see." Rather than using the method of vectors -- use the method of moments to analyze it and see what you get. The most efficient method of moving any mass is by rotations -- either directly or indirectly.
Second-- the resistance in your scenario is from ground friction. Think about how to defeat the ground friction of the mass using cycles of motion. Think about how without pushing on anything you get a swing to swing higher. It is a critically resonant pulse. Do that to the mass. People in some respects are easier because they are reflexively responsive to resonant pulses. What is going on in the body to do those things reflects what is being done outside the body by doing them.