jbriggs444's latest activity
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jbriggs444 replied to the thread Undergrad Acceleration on an electric unicycle, how much does the rider have to lean?.I can ride a real unicycle. One cannot spontaneously lean forward. Instead, one pedals slightly back. This moves the contact point... -
jbriggs444 replied to the thread Chain falling out of a horizontal tube onto a table.The "it" in that passage is the tube. The top of the tube exerts a downward force to impart downward momentum to the chain. The right...
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jbriggs444 replied to the thread Chain falling out of a horizontal tube onto a table.A leftward force to bring the chain to a stop horizontally. And a downward force to bring the chain to a matching rate of motion vertically.
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jbriggs444 replied to the thread Chain falling out of a horizontal tube onto a table.The drawing shows the chain descending vertically. Not in some sort of [evolving!] parabola. This implies that the chain is constrained...
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jbriggs444 replied to the thread Collection of Lame Jokes.They just haven't been exposed to an orthogonal instruction set...
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jbriggs444 replied to the thread Undergrad Conservation of angular momentum in the iceskater example.As the skater's hands are pulled in, they trace out a spiral trajectory. A purely radial force has a non-zero component along the...
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jbriggs444 replied to the thread Undergrad Is calling fictitious forces "not real" just about terminology?.I disagree. The equations are about correlation, not causation. It is attractive to imagine ourselves in the driver's seat "causing"...
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jbriggs444 replied to the thread Undergrad Is calling fictitious forces "not real" just about terminology?.This intuition is a non-starter. Energy depends on reference frame. Causality (to the extent that we have a viable definition to go on)...
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jbriggs444 replied to the thread Chain falling out of a horizontal tube onto a table.The claim that ##\vec F_\text{ext}## is given by ##\lambda hg(-\hat j) + \lambda \frac {\Delta x}{\Delta t}v \hat j## is clearly...
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jbriggs444 replied to the thread Chain falling out of a horizontal tube onto a table.I agree completely. The chain traverses a one dimensional fixed path. There is no net force nor freedom to move other than along the...
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jbriggs444 reacted to haruspex's post in the thread Chain falling out of a horizontal tube onto a table with
Like.
I alluded to that in post #44, but I think it is ok because we can instead view it in terms a tension transmitted around the curve and... -
jbriggs444 replied to the thread Chain falling out of a horizontal tube onto a table.It could if, for instance, we let the chain ride in a frictionless tube on the table. Then the section of chain in the tube would be...
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jbriggs444 reacted to haruspex's post in the thread Chain falling out of a horizontal tube onto a table with Like.
Since the problem statement does not specify what happens to the chain on reaching the table we have to make a reasonable guess about...
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jbriggs444 reacted to PeroK's post in the thread Undergrad Is calling fictitious forces "not real" just about terminology? with Like.
That's nearer to what I would say. But, if someone wants to say pushing a wall and the wall pushing back is cause and effect, then I'm...
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jbriggs444 replied to the thread Undergrad Is calling fictitious forces "not real" just about terminology?.Correlation is not the same as causation. I would say that it is possible for some state of affairs to "cause" a Newton's third law...