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location New England (USA)
age 53
visits member for 1 year, 9 months
seen 12 secs ago

I have formal training in physics, but tend to approach it very intuitively; I prefer estimation over exact calculation, principles over details. I believe many problems can be solved by making a careful sketch. Label your axes, and don't use insignificant digits.

I visit this site in the hope of sharing my enthusiasm and occasional insights with others.


12h
answered Working out length of taut rope orbiting the earth remaining straight and radially directed
1d
comment Charles Law inverse for cooling?
I think you got that opening statement backwards
1d
comment How does $p=fv$ hold when $v=0$ and an engine is working?
It would take an infinite amount of time and infinite work to get up to infinite speed (even then relativity will actually prevent it). Make sense?
2d
comment Can a car get better mileage driving over hills?
I will see how boring this next segment of flight is and how well the WiFi works...
2d
comment Can a car get better mileage driving over hills?
Your hypermiling result for slope sounds wrong. If you climb a single slope at the most efficient rpm, then coast to maintain constant speed, total energy dissipated must be lower than is achieved with the variable speed of the on-off car on the flat. Unless your engine pulsing happens with zero penalty (essentially creating a "class D engine") . If starting the engine has a finite penalty the slope wins because the engine is only used once at the most efficient speed/torque.
2d
comment Can a car get better mileage driving over hills?
I am surprised to see I am the first person to upvote this. I believe you hit the essence of the problem. Eliminating internal friction of the engine is the biggest gain, and a well known trick in the ultra fuel conservation community.
2d
comment Can a car get better mileage driving over hills?
Characteristically detailed, as usual - but I think you can do significantly better than your answer by turning the engine off when you don't need power from it. That $P_0 = 6kW$ is bugging me...
Apr
22
comment Why isn't the magnitude of the electric field in a circuit zero?
In the dynamic case you are always doing more work on electrons - not so in the static case.
Apr
21
comment Why does the lake surface appear darker in some areas?
Yes, that's absolutely what the wind does. See for example this earlier question and the answers / links therein.
Apr
21
answered Movement of accelerating points with maximum speed (i.e. running away from tiger)
Apr
21
comment Electric field on conductor surface
Did you see this answer to a similar question? Does that clear things up for you?
Apr
21
answered Why isn't the magnitude of the electric field in a circuit zero?
Apr
21
revised What physical quantity can be deduced from an activity vs. time half-life decay graph?
added 122 characters in body
Apr
21
comment What is the pressure of falling water?
@DaveGardner most likely yes.
Apr
21
answered What is the pressure of falling water?
Apr
21
comment Frictional force
Please note that "do my homework for me" questions like these, which show no effort on your part to understand the issue or narrow down your problem to a conceptual difficulty, are not welcome on this site (as clearly explained in the help section).
Apr
21
comment When moving from one position to another at a constant velocity, how does the conservation of energy hold?
Upvoting for that last sentence... Indeed if you imagine the sloth falls on a spring, you can see where the energy has gone (and where the work was done).
Apr
21
comment Approximating the moment of inertia of a quadcopter
I think a sphere is a terrible model to use - probably a collection of rods would be better. Because these things go with distance squared, a small error makes a big difference. Solid sphere: $\frac25 m r^2$, hollow sphere: $\frac23 m r^2$ - a more than 50% difference. How close are you trying to get?
Apr
20
answered How can I rearrange an equation to find a gradient for a capacitor?
Apr
20
comment How can I rearrange an equation to find a gradient for a capacitor?
As written I don't think what you state can be proven unless certain other assumptions are made. What is this $T$ you are plotting? Time until what?