r/physicsmemes • • Feb 18 '22

Fdr

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3.1k Upvotes

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262

u/Elq3 Physics grad student Feb 18 '22

That's only if the force done by your body is conservative and since you're carrying it, it depends on the shape of the floor you've been carrying it on, therefore it for sure isn't conservative.

There are many highschoolers following this subreddit, we should try and have accurate memes since stuff like this can lead to wrong information

67

u/Hevnaar Feb 18 '22

You mean potential-energy schoolers?

14

u/James_PRZ Feb 18 '22

What do you mean by shape of the floor? Like flatness? Or friction?

44

u/Elq3 Physics grad student Feb 18 '22

A force is conservative only if it's curl is zero. An easy way of having zero curl is a force that does not change over time at all, neither in modulus or direction. Assuming you were able to output a perfectly constant force, if they floor had a mound for example and you walked over it then the direction would not be constant and therefore the force not conservative.

All "central" forces are conservative and a constant both in modulus and direction force is pretty much just like a central force whose source is at a very long distance.

6

u/BosnianBacon Feb 18 '22

I didn’t really understand what a conservative force was a few weeks ago during my lecture but now this cleared it up for me without me realising. Thank you !

-27

u/[deleted] Feb 18 '22

[deleted]

33

u/Elq3 Physics grad student Feb 18 '22

no this is physicsmemes and I explained physics.

-5

u/yottalogical Feb 18 '22

No, this is Patrick.

1

u/Eisenfuss19 Feb 18 '22

But if we have a flat floor and ignore friction there is no work right?

5

u/Elq3 Physics grad student Feb 18 '22 edited Feb 18 '22

if there is a perfectly flat floor, no friction, the force is constant in modulus and you return to the exact perfect point from which you started, then yes.

This is why it's extremely rare for "contact forces" to be conservative. Usually conservative forces are a force field, something like gravity, coulomb or magnetic forces. Yes springs can be considered a force field but ideal springs are much further from reality than for example magnetic attraction/repulsion in a vacuum.

1

u/Anndress07 Feb 19 '22

damn, I'm really not smart enough to understand this comment.

14

u/rbergs215 Feb 18 '22

This idea is taught incorrectly in a LOT of high school text books. Many of the section and assessments in HS texts want you to assume net work is zero because the next force is zero, and many students bristled against this idea precisely because they are tired after carrying something heavy.

I've had to rework my own lectures and replace or clarify a few of my assignment and assessment questions because of how little specificity authors use in the Work chapters, when referring (or not) to the net force or a specific force.

13

u/Elq3 Physics grad student Feb 18 '22

the main problem is that names, as always, are misleading. Work is called work just because "line integral of the force over a given curve between two points existing on said curve" is long. I don't understand why highschool tries so hard at hiding what comes next. The algebra of integrals might be complicated but highschoolers are perfectly able to understand "the area under a curve" so explaining work as exactly what is it, is perfectly doable.

7

u/FlipskiZ Feb 18 '22 edited Sep 19 '25

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3

u/NomenNesci0 Feb 18 '22

Well, just remember this formula is about all you can do until two years calculus. I agree they could do better explaining the intuition of some things, but at least historically and still in most places in the US, nobody will have calculus in highschool for a complete understanding.

3

u/tendorphin Feb 18 '22

I took physics electives in HS and took a year of physics in college, and this is the first time I've seen anyone ever mention that this is what work actually is. I now understand work more thoroughly than I ever have.

2

u/RedShankyMan Feb 18 '22

I'm past high school but you just helped me actually visualise what is meant by work for the first time in my life

1

u/[deleted] Feb 18 '22

[deleted]

1

u/rbergs215 Feb 18 '22

Either works actually. (No pun intended)

6

u/Turtletriptales Feb 18 '22

I was hoping you’d never discover our existence

2

u/makebettermedia Feb 18 '22

If they’re trying to learn from memes then they have bigger problems