Insights Corrections to MIT Open Courseware: Systems of Varying Mass

[haruspex]

Corrections to
MIT Open Courseware 8-01sc classical mechanics,
fall 2016
Applying Newton’s Laws to systems of Varying Mass
PDF Course Link
My concerns with the solutions provided on the cited MIT Open Courseware web page are, mostly:


Despite arriving at the correct answers, the algebraic methods are invalid. As a result, they can be utterly confusing to the student.
The main flaw, repeated throughout, is writing a system state (momentum) as a function of time only, but effectively defining it as a function of two variables. In some places, this leads to contradictory equations.


This mangled treatment likely results from an attempt to use $F=\frac {dp}{dt}$ in conjunction with $\frac{dp}{dt}=m\frac{dv}{dt}+\frac{dm}{dt}v$, instead of the...

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[neilparker62]

That's a bit concerning. I usually take material from MIT as being pretty much 'gospel' !