There seems to be a lot of confusion about "mass" and "weight." This is likely due to the fact that the English dictionary has many definitions for each of these words, so they often get used interchangeably in everyday conversation. Most of those definitions are irrelevant for this video because, in a discussion about physics, the physics definition (if it exists) always takes priority. So let's properly define our terms: *Mass - The amount of matter in an object. It's measured in kilograms or slugs.* In Newtonian mechanics, mass stays the same no matter where you are or what you're doing. If my clone is 75 kg on Earth, then he's also 75 kg in an accelerating elevator and in low-Earth orbit and in deep space. The amount of matter inside you doesn't depend on those things. *Weight - The force of gravity from a large object (like a planet). It's measured in pounds or newtons.* That's it. It's just what we call the force of gravity in the situation when one mass is much larger than the other. I defined it at 1:49. This definition can be found in any introductory physics textbook. I even posted a few pictures from those textbooks on Twitter: twitter.com/NickLucid/status/1410763207879368705 Weight is the same no matter what you're doing. In an elevator, my clone has a weight of 165 pounds regardless of acceleration. Weight is _not_ the same regardless of where you are. My clone is 165 pounds on the ground, but he's 140 pounds on the ISS,and he's zero pounds very far from larges masses like stars, planets, and moons. You have to get _really_ far away for this to be a factor though. The top floor of a building isn't far enough. In a building, weight doesn't change. *Which does a scale measure?* Neither. Mass isn't even a force, so there's no way a scale could measure it. _I didn't bring it up in the video because it wasn't relevant._ Since weight is a force, you might expect the scale could measure it, but it doesn't. Scales can only measure forces that require physical contact and weight isn't a contact force. Push scales measure normal force. Pull scales measure tension. Thank you for coming to my TED Talk.

I'm reminded of Hitchhiker's Guide to the Galaxy which states that flying requires learning how to throw yourself at the ground and miss...

_I didn't forget about it. I ignored it._ Spoken like a true physicist. 😂

For an even more straightforward example of "normal force" on a scale, try putting your scale on an incline. It won't give your entire weight, only the weight that's normal to the surface the scale is sitting on.

So I've just learned that scales work exactly how I've known they have for my entire life. I thought this video was going to blow my mind or something

Careful. Using the scale other than as intended may void its warranty.

You're a braver man than I referring to your wife as "or whatever" 🤣

I remember doing this in my high school physics class and it was probably one of the most interesting lessons we did. The fun lessons like that are what made me love science in general, good teachers know how to keep class interesting.

“You don’t feel weight, you only feel pushes and pulls”… man I feel enlightened, thanks for the video

As a kid I started to have this same suspicion about what scales actually measured when I held the bottom half down and pulled the top half up and watched the dial spin the other way, effectively displaying what I called negative weight. I realized then it was measuring how hard I was pulling or pushing on it. 34 years later you make a video expertly explaining what me as a 10 year old was seeing. What other childhood observations will you help explain next? 😄 Great video!

7:04 I disagree. The buoyancy force on snow and slush are both completely negligible. The reason slush is harder to shovel is that it is more dense, and so a shovel-full has a greater mass than a shovel-full of snow.

Just brilliant. I've been trying to explain this thing about scales, lifts and gravity to my son - but nowhere near as well as this. I can't wait to show him this video when he comes home from school later. Huge thanks, Science Guy!

"This isn't flying, it's falling with style".

“The Guide says there is an art to flying", said Ford, "or rather a knack. The knack lies in learning how to throw yourself at the ground and miss.”

I remember my first ever physics lesson in school about 8 years ago. The teacher talked about the difference between mass and weight. I was so fascinated that physics became my favourite subject on that day!

I've already went there with my mind... no need to physically take a scale anywhere. Thanks for the superb content; You are truly in my book as the gangsta of science within your respective fields!!!👍🏽🖖🏾

what makes this funny is that I have an elevator scale in my bathroom.

"Falling but missing" is some hitchhikers guide to the galaxy stuff

This brought back to mind my days of running cranes. The point in time in which a load is lifted that it begins movement “going up” no matter what it is it becomes heavier for a fraction of a second. Depending on the speed at which it’s being hoisted that force can actually overload a crane. I remember learning in my crane certification classes that this point in time of initial force is called the moment of load. Interesting that I I’ve never even considered it since then in the elevator of all places.

As a kid we liked to jump when the elevator started moving. You will either go up more or less than expected.

You can use this effect in an elevator, when carrying grocery bags. When you enter the elevator in the parking floor, place the bags on the floor. Just before you reach your floor and the elevator begins to stop, lift you bags up again and they will be much lighter. This need perfect timing, but it works great.

Turn the scale upside down. The Earth now weighs ~your earth weight~ on planet You.

Thanks for the fantastic idea for my IB Physics Class!

2:50 falling sideways. falling and missing... Douglas Adams had this to say about it in The Hitchhikers Guide to the Galaxy... "There is an art to flying, or rather a knack. The knack lies in learning how to throw yourself at the ground and miss. ... Clearly, it is this second part, the missing, that presents the difficulties" According to the Guide, the main thing that flying requires is the ability to throw yourself at the ground and miss. It says to throw yourself forward with all your weight and "the willingness not to mind that it's going to hurt", however it will surely hurt if you fail to miss the ground. The difficulty is in missing the ground, and doing so accidentally, as "deliberately intending to miss the ground" does not work.

I honestly thought that's what weight meant. All my life I said weight changes with forces, mass stays constant.

3:25 footage of astronauts performing important science on the ISS

Nick, you're very informative and entertaining to watch. Thank you

Great presentation, brings back memories of my youth when I was really into technical things.

WHY NOT ?!? Cheers!

Could picture Nick getting kicked out of a building for playing in the elevator with a scale. 🤣

that little throw away few seconds finnaly allowed me to know what 'normal' is in forces. and we alllll forget about buoyancy... most times.

was much more interesting than I thought. Dude youre making great videos!

1:19 I love the way that Nerd Clone always looks at the camera after saying something technically correct.

Reminds me of the first time when I learned that mass and weight are different things, back in high school in the 90s. Much needed for the new generations.

Hey! I have a bone to pick! I was relegated to watching a rerun because you haven't posted a video in three weeks even though you usually do one every month. (P.S. I still enjoyed it)

this is the first vid I see and subbed immediately. Very interesting and very well explained, also it's refreshing to change perspective on the mundane.

Very interesting! I had to do this exact experiment as a project for my AP Physics class years ago. Teacher told us to bring a bathroom scale on an elevator, videotape the change in measured weight, and use the footage to calculate the maximum and minimum acceleration of the elevator, exactly as you did here.

In my language we use this definition: Weight is the force with which the body pushes the support or pulls the suspension. (when we translate our word for weight) But then you call gravitational force weight and our "weight" apparent weight.

I really like your style of teaching. I have watched almost all of your videos. I really used to like the style of the one which you made a year back around or so would like to see more of it.

wow u blew my mind i love the way you explain things

I was confused after seeing the title but then realised that the word in my language that translates to weight actually doesn't translate to weight at all, at least according to this video. In Lithuanian, "weight" is translated as "svoris" and is used that way in linguistics, dictionaries, every day language, etc. That's the official translation. However, it seems that "weight" does not mean "svoris" according to this video. We use "svoris" to describe the force that an object affects another surface, say, the ground or the scale, which is what you called the "push". We use the word "sunkis" to describe the force that gravity pulls you downward with (or towards another mass). And "sunkis" translates to "heaviness" in English instead of "weight". So the official translation of "weight" actually doesn't mean weight in Lithuanian. And the official translation of "heaviness" actually should be the translation of "weight". Interesting how linguistics and physics can differ so much, especially when different languages are concerned. EDIT: After some digging, I found that it's English physicists that's to blame for the misconception of weight and the weird "mistranslation" between English and Lithuanian. The word "weight" comes from Old-Germanic "wegan" which comes from Proto-Indo-European "wegh". And it means to move, carry, lift. So English physicists incorrectly chose the word "weight" to represent the force of gravity when it should have represented the push force that objects affect surfaces such as the ground or the scales since it's exactly THAT force that ancient people felt when they came up with the word "wegh/wegan". Apparent weight should be THE weight and what is weight in physics should probably use another word. So maybe it's not the people who say scales measure weight who are wrong but rather physicists who chose the wrong word?

Didn't encounter this question yet but thank you for making my concept more clear.❤️

3:02 "Flying is easy, just throw yourself at the ground and miss" --Douglas Adams

What a fantastic post!!!! thank you :)

I didn't realize the importance of knowing these concepts until I found this channel! there's no words to describe this "THANK YOU!" that i'm feeling!

This channel is so good it literally explains physics in a fun and understandable way

All the science stuff and all was really cool, but then I saw the TMNT shirt and I had tu sub. Great content!

“There is an art to flying, or rather a knack. The knack lies in learning how to throw yourself at the ground and miss.” - Douglas Adama

As I child I thought it would be funny to jump onto a scale. The result was that the meter jumped up and that I gained some intuitive understanding of this.

I've taken many physics courses in my engineering education and never had an issue with the idea of weight. We always calculated and described weight as the product of mass in the presence of a gravitational field. Weight is an object's mass multiplied by acceleration of gravity. Some of this seems to muddy that concept.

Thanks for the video.

The symmetry of this new set up is something else. He's either in the middle right down the line between the walls of there's 2 of him one on each side.

3:03 HOLY F! The Hitchhiker’s Guide to the Galaxy was right about flying!

Thank you for explaining the difference between normal and perpendicular. I always wondered.

This is a very clever video right from the title! I salute you sir!

Surprisingly I have always explained how bathroom scales work the same way. Nice video.

cool! thx for helping me in my 3rd secondary year dynamics keep it up man !

Definitely keeping this in my video list for my class. Thank you so much

Wow. I thought I were doing an odd thing by placing the scale on a spring mattress and bouncing up and down, to see the different readings when going up and when going down. A digital scale doesn't work well, because their sampling rate is too low - one per second, or less. One similarly interesting experiment, is to take a GPS speed meter on a motor boat, and comparing the reading to the speed indicator of the boat, which indicates the speed relative to the water - it uses a small turbine in the water. Or comparing it to the wind speed. Speed is so much more relative than weight... Thanks for the video...

*Elevator barely has room* Me: *pulls up with a bathroom scale FOR SCIENCE*

Even a lot of engineering graduates don't understand these fundamentals. This video is gonna be a great help to high schoolers, I remember my own suffering trying to understand this two years ago XD

I read the title. And immediately thought: "To prove Einstein right." haven't seen the video yet.

Such a great video!

Your videos are becoming more and more pieces of art.

Huh, I didn't connect this in my mind till now, but Douglas Adams' thing that flying is throwing yourself at the ground and missing has a basis in reality.

Good and illustrating video as always! What could be added regarding the old fashioned analogue scale, is the much higher weight measured once you step on it and before it stabilizes at static rest (I mean at the static floor now, not in the moving elevator). This is not a measuring error, it is in fact a true measure also due to sudden or moving load (not to be confused with impact loading) 🤓. Now, it's a shame the digital scales do not show the beauty of this as the added acceleration just when you step on the scale is not shown, at least not on my digital scale. The sudden or moving load is not equivalent to the static load measured at rest, even it's not an impact loading that is usually asociated with even shorter load duration.🤓keep up the good work, your videos are truly interesting and illustrates physics in a fascinating, educational and not to forget in a crazyfunny way!👍😊

You have some interesting characters on your staff. 💫🙇🏻

There seem to be at least three different definitions of the word "weight". 1) Mass m in kg (as understood by most people and intended to be measured by the bathroom scales) 2) Force of gravity, mg in Newtons, as defined by US/EU textbooks 3) Force applied to a support, m(g+p) in Newtons, as defined by some Eastern European textbooks.

I’ve had to explain this to my students so many times and they think I’m crazy because no one else explains it this way.

“The channel where you learn about physics and have fun doing it!” All of KZfaq should do this.

Another fantastic video ! I ❤️the science and I ❤️ the humor!

I don't feel I need to for the simple fact that you did it for us. Thank you sir, great content

Sir, you have cleared my confusion of mass and weight. Thanks Sir. I would say only one thing after viewing this [great] video - 'This is the best Science channel on KZfaq for [crazy] people like me.'

"There is an art to flying, or rather a knack. The knack lies in learning how to throw yourself at the ground and miss." -- Hitchhiker's Guide to the Galaxy

wow i just found you through your other channel where you talked about autism, i was diagnosed later than usual as well and it was tough. Seeing what you have achieved here and your great communication skills it gives me some hope :)

Nick, i love ya! The way you explain things is perfect for a goofball like me! Keep being awesome!

Your videos are awesome. Thank you very much. Now I’m going to put my scale in a swimming pool and see what happens next.

If you turn the scale upside down, you can measure the force of the Earth on you (unsurprisingly identical to your force on Earth)

Your elevator demo is done with a spring-based scale. Now try it with a balance scale and see if it'll register those up-down blips.

Dr Nick, you're one of the best at explaining Physics. Would you consider making a series of video about Loop Quantum Gravity? Something about Loops as solution to the Wheeler-Devitt equation, Spin Networks, Volume as a quantum property of a node and Area as quantum property of a link, the emergence of "Space" from a Spin Network, Spin Foam and the emergence of "Time" from the evolution of a Spin Network. LQG is a very neglected topic, it's very hard to find good material...

1 minute in and this is already the exact video I needed today. Last week I realized that astronauts experience serious gravity being ostensibly weightless and that sent me down a gravitational rabbit hole that this video just capped off.

Till this day I don't regret ever subscribing!

Great video! I have these talks with my two boys, all the time!👍😉

best physics guy out there! Continue with the good job!

Space Clone might want to have his propulsion mechanism checked. Green could be a warning sign.

I will agree, you can’t feel “weight” what you feel is the normal force for the required acceleration. As in an aircraft, in a pull-up, “pulling gs” what your are feeling is the normal force, being provided by the seat of the aircraft, to accelerate you. Hence, if you are sitting on a scale in the aircraft you will see the required force to accelerate you with the aircrafts changing flight path (velocity)

in wikipedia article "mass versus weight! we can find "The mass of an object is a measure of the object’s inertial property, or the amount of matter it contains. The weight of an object is a measure of the force exerted on the object by gravity, or the force needed to support it. " that are the correct definitions

They measure force put into them. You can make make that number bigger by just pressing it stronger

"Falling, but missing..." Is that a Douglas Adams reference?

So Douglas Adams was right. Flying is just falling down and missing the ground.

what would happen if a person in an broken elevator which is falling down suddenly jumps just when it is about to crash on the ground would the person feel impact?

You didn't mention that the "weight" on a scale is also influenced by the rotation of the Earth. The closer to the equator you are, the lower your weight is on a scale because of the apparent centrifugal force (you're also more far from the center of the Earth).

"Hey honey, I need your help for a video!" "Ok, what do you need me to do?" "Stand here while I push the bathroom scale against your back!" ... ... ... "Ooookaaaaaayy...."

Actually (nerd clone here) the scale measures the normal force with which YOU push on the scale. Yes, it has equal in magnitude to the normal force with which the scale pushes on you because they are an action-and-reaction pair, but still. The scale can only measure a force acting on it, not a force acting on you. Which is another very good reason why a scale could never measure your weight (which also acts on you, not on the scale). Brilliant video.

Having pushed on a scale with my hand, it was quickly obvious that it wasn't measuring weight. But given the regular context it is meant to be used, across generally consistent frames of reference, one can note the changing variable.

PROFESSOR!! I shouldn't say your last name here!! You inspired me with your physics 1 class and I passed the Civil PE in Water Resources & Environmental this past October. I think of you fondly, and often. The history of physics is still the best thing I've ever learned and I have you to thank for my career path. I found this channel while looking for you so that I might thank you.

yes i was just going to grab my bathroom scale to measure my elevators acceleration

Dude you're so good at getting angry with your nerd clone, lmao. I bet a lot of work went into figuring out how to time that just right, with the i-i-i -it, and head shaking. Or maybe your just a brilliant genius who had an innate sense for how to deal with nerd clone.

Its like two days I find your page and I have a lots of exams but I don't care and I just watch your videos 😁👌🏻so nice video ♥ you show the real since🤝🏻

My God I had always wondered but never got an answer. So thank you