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location New England (USA)
age 52
visits member for 1 year, 8 months
seen 4 hours 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.


4h
comment A horribly oversimplified question about matter
Did you read the answers to the question suggested as a duplicate?
4h
comment A level 9702/11/o/n/14 question 26 (about interference of sound wave)
The power supplied to the speakers might be the same but the distance is not - so when the two are in anti-phase, they don't have the same amplitude at the point of detection.
5h
comment Doesn't a box holding a vacuum weigh the same as a box full of air?
The box weighs the same - it's the contents that have a different weight...
7h
answered Finding final velocity in inelastic collision
7h
comment Finding final velocity in inelastic collision
The horizontal component of the speed must be the same as it leaves the chute and as it lands - the angle is no longer 37 degrees though...
8h
comment Back EMF in an electric motor
Only if it could do work without drawing power. I'm sorry but this feels like a "if I could turn off gravity, would I be able to fly" kind of question. I am voting as "off topic".
8h
comment magnetic field due to current in a wire using Biot-Savart's law
Draw a little diagram for yourself - I suspect that your sign goes awry in the transformation from $ds$ to $d\theta$ but without a picture it's hard to know for sure.
9h
answered Deriving an Euler Equation
10h
comment Do greenhouse gasses make the world habitable?
Although I agree with most of what you say, it doesn't obviously follow (you said "so it's pretty obvious") from your earth/moon argument that it's the atmosphere that is causing the difference (although I happen to think it does) - for example, what about the natural radioactivity in the respective cores (earth is larger, therefore even with same composition it would have more radioactive material vs surface over which to lose that power)? What about the albedo? What about the water in the oceans (70% of the earth's surface) absorbing solar heat?
11h
answered Mass-Spring system on an accelerating jet
11h
comment How much magnetic field will be required to levitate a human?
This is closely related to an earlier question physics.stackexchange.com/q/15747/26969 and should probably be marked as a duplicate
12h
comment How much magnetic field will be required to levitate a human?
@irishphysics I don't think that quite works - it's the gradient of the field that matters not the magnitude. And you don't know how far the frog might drop (in other words what value to pick for h) - the equilibrium position is where the gradient squared (averaged over the volume of the frog) is the right value.
12h
comment How much magnetic field will be required to levitate a human?
@zeldredge - that scrawny kid that everyone picks on?
12h
answered How much magnetic field will be required to levitate a human?
12h
comment Why does $F=ma$? Is there a straightforward reason?
@user36790 - do you happen to know what book it was?
12h
revised Why does $F=ma$? Is there a straightforward reason?
added 729 characters in body
13h
revised How much magnetic field will be required to levitate a human?
Made question clearer based on content of video
13h
comment Variable Gear System
This is an incredibly complex "first question"! I suggest that you draw a little reference "dot" on every part, and try to figure out how each part moves relative to each other part if the input wheel moves by a small amount. In other words, draw the system in two states that are just a short distance apart. Geometry should then do the rest. I have difficulty following the operation in fig 4/5 - but you obviously understand it so you are probably the best person to answer your own question...
13h
comment The Coefficient of Restitution of a bouncing ball
I hope you don't mind I made a couple of small edits just to clean up the answer - but without detracting from its simplicity and correctness.
13h
comment Why does $F=ma$? Is there a straightforward reason?
I realize the second argument needs to be constructed a bit more carefully. I will be back when I can make a diagram...