Calculating average velocity or speed | One-dimensional motion | Physics | Khan Academy

Example of calculating speed and velocity. Created by Sal Khan.

Physics on Khan Academy: Physics is the study of the basic principles that govern the physical world around us. We'll start by looking at motion itself. Then, we'll learn about forces, momentum, energy, and other concepts in lots of different physical situations. To get the most out of physics, you'll need a solid understanding of algebra and a basic understanding of trigonometry.

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[punnenlol]

If anyone wants to know a shortcut for converting km/h --> m/s, you simply divide by 3.6. Likewise, if you want to convert m/s --> km/h, just multiply by 3.6.

For instance:
5km/h/3.6=1.39m/s
5m/s*3.6=18km/h

You'll probably need a calculator, but it's extremely helpful during exams and such. If you don't think it's right, check it on your calculator!

[tdiggity]

The real magic here is how he writes with a mouse

[manalayesha]

" s" in displacement came from the German word “strecke”, which means route in English. Another answer indicates that this probably came from the Latin word for space - “spatium”. This is also possible as the vector <s> actually indicated position and Δ<s> is what indicates displacement. I think these are more likely reason, more than ‘S’ looking like a curve path.
However to verify we need to dig into the history of science. Mechanics was first formalized in mediaeval Arab world and its quiet possible that ‘s’ for position is a historical remnant from there. The German/Latin origin hypothesis can also be verified following the same route.

[thedogdogification]

What I appreciate so much about this video is that he is very consistent about writing down the units each time, even if it seems obvious. I've had teachers who skipped writing the units during some steps because they were "obvious" and usually that's where I became confused, because I was trying to understand the concepts while at the _same_ time trying to track which numbers were which and it was too much.

[rockysinai]

Sal, you are the real hero. Here is my take - Those days people wrote scientific things in Latin, displacement is obssesio in Latin, there are 3 sss in that word, so someone used s for displacement. O was already used for the Origin/starting point.
But this is my favorite one I learned from a Physics guru. - Distance was written as small delta, but the handwritten delta after many years of usage of the manuscript got partially erased and looked more like s, and got passed on to the next generation.
Once again, you are the real hero helping millions of kids become educated. Don't know why you haven's received the Nobel prize for Peace yet.
Just saw Aira's comment, she has a better answer.

[deepagusain]

The actual reason why 's' is used for distance or displacement is that:-
The Latin word for distance is spatium, which means space or distance in the English language. In this book and many others, the letter s will be used for distance and displacement.

[xavierwellons]

Yall may not see this comment, but ill be a loyal subscriber for this channel as long as keeps going. Frankly I am truly touched by the Khan movement. I never thought I could understand mathematics or physics and this channel has brought to a moment that i'm finally taking bigger steps in astrophysics.

[SandeepAgarmorTutorial]

i have watched your videos .you explaination is very good. any one can learn from this videos

[williamheywood]

Why is the symbol for displacement s?
"S" stands for the Latin word "spatium", which means distance or space.

[yusufchaudhry]

Who else is watching this the night before the exam

[annelegaspi]

"So the best way to cancel this hours in the denominator is by having hours in the nunu.. in the doonumen.. hehe.. in the numerator..." :))) so adorable haha love you Sal

[TheScienceCube]

I had trouble with physics in college. When I signed up I thought it said psychics. But then I found Khan Academy - Thanks Sal!

[dhruvsoni]

Also guys, if you need help converting km/h to m/sec then just multiply the value by 5/18. Most of the times the velocity or speed is a multiple of 18 so this method is very easy. If you want to convert m/sec to km/h then multiply by 18/5

[Playpup]

Thank you so much! I have a physics teacher that tries his best but has never been able to go over anything conceptually well. You've helped so much!

[countingdays]

should atleast put like 1 ad in your video bro, you deserve it

[minjuai]

Who else is watching this in isolation? Now that we’re doing online school.

[jonathanschossig]

I'm from Germany and I always thought it was derived from the word "Strecke" which means distance.

[ireneadler]

I am having exams in October in physics chemistry biology and geography, THANK YOU for making this so easy for me, this video just taught me things my teacher couldn't do for years, I swear if I get rich, I am gonna donate millions !!!!

[mirzijayrexhar]

So nervous but it's ok, thanks for this vid🙏

[hedonism]

As I understand it (not that you'll be reading these comments after three months), s is for displacement because
A) d is for distance, as well as later the derivative.
B) s can stand for space, which is a clearer way of describing displacement.