Recent content by kuruman

Theorists?

This is a good example of why you don't really master a concept until you have to explain it to others, which means that first you have to examine it from all possible angles in order to explain it to yourself before you attempt to explain it to others. In this particular case, a seed could...

Although I used Taylor many times to teach intermediate mechanics, I did not use his method. I showed my students how to do line integrals from first principles. The idea is simple and takes three steps: Write force ##\mathbf F## and displacement ##d\mathbf r## in unit vector notation. Form...

Numerical problems like this are easier to troubleshoot if you (a) express and solve the problem in symbolic form first, then (b) substitute numbers. Here you have (a) ##\mathbf r=at^3~\mathbf{\hat i}+bt~\mathbf{\hat j}+ct^2~\mathbf{\hat k}## ##\dfrac{d^2 \mathbf r}{dt^2}=6at~\mathbf{\hat...

It is true that I was not thinking of gear ratios but a more simplified version such as a tricycle with no gears. The trike will move forward regardless of whether you pull with the yellow force or the red force.

It's a simple application of Newton's Second Law. (a) If the bicycle rolls without slipping, the IPOC (Instantaneous Point Of Contact) of the wheels and the floor is at rest regardless of which way the bicycle moves. (b) Tie a piece of string on either pedal and pull standing behind the bike...

Why does it mean that? What exactly are those changes in internal energy? The change from what point of the process to what other point of the process?

You don't need Clausius-Clapeyron equation for this. In post #19 it's more a misuse than a mistake. In this problem you have an amount of water just at the boiling point at atmospheric pressure. You add a little bit of heat Q and a certain number of water molecules come out as steam which you...

First of all, @songoku who posted the problem; we are here to help along a path to the solution. Secondly, you can see for yourself that your last equation is problematic in that the heat that you calculated is independent of pressure. In other words, whether the pressure is atmospheric or...

I don't think that one has to go to Clausius-Clapeyron for this. It looks like energy conservation to me as the OP started doing. You add heat ΔQ to water at the boiling point and you end up with most of the water at the boiling point, with some having been converted to steam under pressure. The...

All that is true, but it does not address OP question which was whether the rationale behind the rules for algebraic manipulations needs to be explained right from the start. At that point all one needs to show is that whatever rule one applies to find a value for ##x## can be verified by going...

These are just names. What specific expressions for each one of them do you think you can use to relate them to relevant quantities in the problem?

You are absolutely correct. I was a bit hasty cutting and pasting labels in the figure. The original post has been edited.

For a meaningful comparison, one needs a controlled process. What I have in mind is the thought experiment shown on the right. Start with two identical cylindrical vessels containing identical amounts of water at 100oC. Cap both vessels with a piston of negligible mass. Put some extra weight...

Higher than what? You have to put it together with specific equations, not words. Yes, my oversight. What exactly are the meanings of ΔU, ΔKE and ΔPE when you convert an amount of water into steam? You need to be clear about that before manipulating equations. Post #9 has a useful hint.