Physics Question

[sailorchic34]

Originally Posted by barnakiel

We need energy to shoot up a sputnik but a sputnik will fall down by itself.

Same story with an escalator - one needs more energy per step when the escalator is moving up.

b.

Nope, not when your at the same velocity as the escalator.

[Stu Jackson]

Originally Posted by sailorchic34

Nope, not when your at the same velocity as the escalator.

Agreed. Almost scary when folks don't "get" this. The OP isn't 'evil, evil" he's just "provocative!"

[Weyalan]

Originally Posted by sailorchic34

.

But if your on the escalator at tau 0.7, from your reference frame, nothing has changed. It's only from an external reference frame that there is contraction.

I think I have come to the conclusion that the OP is a evil evil man. Such a simple question and zoom, we run smack into reference frames and general relativity.

Yeah, but I was just stirring the pot / muddying the waters, lol.

[sailorchic34]

Originally Posted by Weyalan

Yeah, but I was just stirring the pot / muddying the waters, lol.

and stir you did...

[msponer]

I only half agree with any one of you.

The question is "energy expended" -- which needs a knowledge of physiology that hasn't been discussed: of course you have to push more onto your foot, and then equally less, to accelerate and decelerate at the top and bottom of the escalator. That's easy calculate precisely.

But the question is how does that affect energy expended. And that requires physiology that I don't know. Are legs and feet, as a system, symmetrical in their energy expended, so that whatever additional work they do to accelerate you on the first step is equal to what they must not do to decelerate you on the last step?

I'm guessing no. Does lifting 10 pounds 100 times and lifting 8 pounds 125 times yield exactly the same feeling of tiredness in your arms? They are equivalent work from a physics perspective, but I'm guessing they aren't to one's body.

The escalator problem is like that. The first step is ~11 pounds. The middle steps are ~10 pounds. The last step is ~9 pounds. Or whatever. But is your body's energy expenditure algebraic like that, where 11+10+10+9 = 10+10+10+10 ?

[barnakiel]

Originally Posted by sailorchic34

Nope, not when your at the same velocity as the escalator.

You will be correct. I will have to think again.

I may have mixed up acceleration with the other thing.

Otherwise it could be pretty difficult to get back to my first class seat from that toilet situated somewhat aft in the fuselage ...

Getting caught out gets less and less painful the longer I've been around.

;-)
b.

[Adelie]

Once you are on the escalator you are expending the same amount of energy climbing X treads as you would on a fixed stairs, once you are on the escalator you are in the frame of reference for the rising treads. This is more of a potential energy question than kinetic energy.

Don't get into the math behind this, down that road lies madness and relativity.

[sailorchic34]

Originally Posted by barnakiel

You will be correct. I will have to think again.

I may have mixed up acceleration with the other thing.

Otherwise it could be pretty difficult to get back to my first class seat from that toilet situated somewhat aft in the fuselage ...

Getting caught out gets less and less painful the longer I've been around.

;-)
b.

No worries it seems simple and it sort of is except there's relativity involved which I think actually does lead to madness

[Wotname]

Hmm… fast moving thread and plenty of drift; I see the OP's question is probably answered by now and so a little more drift is in order .

I'm walking up the "up" escalator and holding a smallish piece of wooden companionway coaming vertically in my left hand and have a pot of open vanish hanging off my belt. With my right hand, I'm applying the said varnish to the wood with a quality brush.

Should I apply finishing strokes of the varnish in vertically up strokes or vertically down strokes in order to get the best finish?

Not knowing has been keeping me awake at nights, please help!

[Adelie]

Originally Posted by Wotname

Hmm… fast moving thread and plenty of drift; I see the OP's question is probably answered by now and so a little more drift is in order .

I'm walking up the "up" escalator and holding a smallish piece of wooden companionway coaming vertically in my left hand and have a pot of open vanish hanging off my belt. With my right hand, I'm applying the said varnish to the wood with a quality brush.

Should I apply finishing strokes of the varnish in vertically up strokes or vertically down strokes in order to get the best finish?

Not knowing has been keeping me awake at nights, please help!

Neither, with the coaming held vertically you are more likely to have sags regardless of which way you stroke, you need to hold it horizontally.

If you are going to stir the pot you need to better than that.

A better question would have been:

Since heat is really an expression of elevated kinetic energy, and you experience added kinetic energy when on an escalator will the varnish dry faster on the escalator than off if since has increased kinetic energy? An will standing or climbing make a difference?

[Wotname]

Originally Posted by Adelie

Neither, with the coaming held vertically you are more likely to have sags regardless of which way you stroke, you need to hold it horizontally.

If you are going to stir the pot you need to better than that.

A better question would have been:

Since heat is really an expression of elevated kinetic energy, and you experience added kinetic energy when on an escalator will the varnish dry faster on the escalator than off if since has increased kinetic energy? An will standing or climbing make a difference?

You are clearly smarter than me
And I don't think I would even understand the answers to the questions that keep you awake at night

[Adelie]

Originally Posted by Wotname

You are clearly smarter than me

Nah, I'm just better at coming up with questions that are intellectual hand jobs.

And I don't think I would even understand the answers to the questions that keep you awake at night

I don't know about keeping me awake at night, but my current intellectual pursuit of little value is answering the question:

How would I make a Cal 20 as fast or faster than a J/24 and under what conditions?

[Weyalan]

Originally Posted by Adelie

I don't know about keeping me awake at night, but my current intellectual pursuit of little value is answering the question:

How would I make a Cal 20 as fast or faster than a J/24 and under what conditions?

Easy: If you take a Cal 20 and a J24 and push them off a cliff, in a vacuum (how you arrange that is up to you), they will be equally as fast.

[Adelie]

Originally Posted by Weyalan

Easy: If you take a Cal 20 and a J24 and push them off a cliff, in a vacuum (how you arrange that is up to you), they will be equally as fast.

Your idea would work, but I meant on the water.

I can see how to do it, but the boat wouldn't be class legal by a long shot.

[jkindredpdx]

Some asked how my question relates to sailing... 3 ways:
1. My boat is sailing through the water at 6knots and I want to walk to the bow, should I slow the boat down to make the walk easier?
B. I'm going to climb my mast, if my first mate is lifting me and my ladder webbing with a winch and I'm climbing in steps tied into the webbing will I need to expend more energy to lift myself from one loop to the next than if she didn't help?
and Finally.... I can't remember.

Oh yea, I provided SailorChick with another opportunity to show off how brilliant she is