Measure height with a watch! Cliff jump science

Mark Rober

2,6 млн переглядів478

    This is a simple trick using high school physics where you can measure the height of really tall objects like a cliff, using just a stopwatch.
    Special thanks to Active Life Store for the GoPro shots. You can get one from them here:
    Here is a link to the FREE app (free as in FREE, as in I don't even have any ads in it or make any money off of it whatsoever) in the app store (sorry, no android at this time):

    I make videos like this once a month all year long while supplies last:
    FOLLOW ON TWITTER: #!/MarkRober
    FACEBOOK ME: MarkRoberUKup

    All music created by Qwiet. You should go sub his channel:
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    Опубліковано 6 років тому


    1. Elijah Dalton


    2. Phyvemin

      The best part is u can even release it with a horizontal velocity

    3. Eric Seif

      “it’s that simple” me still trying to read the title

    4. Rodrick Heffley

      What about the time lag due to speed of sound reaching your ear

    5. Yash Tayde

      11th class science

    6. Jack Sargeant

      correct me if im wrong but cant you get a close estimate on smaller objects by just multiplying the time you get from leaving the top and hitting the water by 9.8?

    7. Azad Muralidhara

      hi im 7 i i love science i cant do math like that

    8. no

      Mark: All you have do is grab your phone and jump into the water Me: *Wait a minute...*

    9. Dr. MJC

      I just hang my Jimmie off the cliff and if it reaches the water it is 32 feet. That water is cold, yeah, and deep too.

    10. Lawrence Johnson

      Other ways to find the height of the cliff with a watch, "I'll give you this nice watch if you can tell me how high the cliff is"

    11. Stephon Walker

      Ok, but what did you really say, where the v.o.'d "compact" was?

    12. Jakub Skowron

      I love the tree height measurement with rock. It's great.

    13. Brajesh

      Cool thing is that guy went to moon to give the proof that all objects fall at same rate irrespective of mass.

    14. Scott Allen

      But the uncertainty in you reaction time on the stopwatch will be about 1/4 second.

    15. Caleb Jackson

      one of my favorite space videos of all time. "How 'bout that!"

    16. Sage D

      I hat if for example you chuck something down a hole and measure it based on sound but because of the large distance it becomes inaccurate as sound can only travel so fast

    17. froggiman1

      It just doesn't make sense to me that a freight train engine car would fall from a cliff as slow as my body would. I am not saying that's incorrect. It is just hard for me to believe.

    18. chemics bear

      OMG I somehow thought you can measure the height of the person by measuring the dropping time

    19. Luke Swinney

      how would you measure the height of a helicopter jump

    20. ZippitZippo

      Can i use this method to measure the empire state building?

    21. end me

      what is the equation for meters?

    22. Sarah Justice

      How funny I just got done learning about this and simular things in science ( and I'm in 6th grade am I supposed to know how to calculate newtons and acceleration due to gravity and how to measure somthig based on how long it took to fall)

    23. Triangle Nilnoc

      Hmmmmmm. Physics tells me that at scout camp when I was 11, I jumped about 144 feet... 16(3)^2 following PEMDAS = 16(9) = 144 I question this.

      1. Colin Southern

        Given that gravity probably hasn't changed a lot since you were 11, I'd take a closer look at the "3" ...

    24. Vojtech Sarik

      yeah using science to count in imperial units .. *facepalm* this guy worked at N.A.S.A he should know better :( but its old video ... with metric system you actually know how physics works, that you have some kind of gravity that accelerates (9.8 m/s) and use "h = 1/2*g*t*t" you and thinking about you falling and accelerating down you can discover new things like you have to start accelerating in first place (you are not instantly getting 9.8 m/s) and about air resistance and drag and you can start count it more precisely and also you are not falling strait down when you jump from cliff you have side motion or if you have initial up or down motion since that will affect the time of drop.. but when i see 16*(x*x) i get nothing in mind :( i don't even know how big foot is .. in metric its easy

    25. Bharadwaj Vemparala

      It would be inaccurate as we have to take air resistance also

    26. Musaddiq Ohi

      I think the pictre for the vid is a bit inappropriate...

      1. David Goettemoeller


    27. Kier Mc

      me watching this at the end of 2020 8:22

    28. Cameron

      back when mark used clickbate

    29. Lander Reyniers

      What is the equation but for the metric system?

    30. Edward Lillis

      with the equation, why do you times it by 16?

    31. Aayushman Kumar

      In india , you have these questions on exam papers

    32. Hatifrey

      At no point was I expecting to see an astronaut holding a hammer and a feather going "Watch THIS."

    33. Shem Shem

      i don't even need to watch this video, I already know its 1/2(9.81)(time)^2 from the title, but I also know that mark probably explained everything in here what took my school a total of 5 hours to teach.

    34. Crystal Nipper

      Me and my brother HATE math And for some reason we’re good at it

    35. Anaxagoras

      “How ‘bout that”

    36. Connoritout

      Who’s watching this is 2020

      1. Zirui Wang

        almost 2021

    37. RMH Bricklaying

      Who got click bated with the bikini lol

      1. Musaddiq Ohi


    38. Benjamin Dunlop

      How to get bowling ball out of water?

    39. Fernanda Castaneda Martinez

      how old are you mark

    40. Thomas G

      *How does a scale measure the weight of different objects, if all objects are attracted by gravity equally?*

    41. Bubbels Playz

      Instructions unclear! Friends did not enjoy being pushed of buildings to figure out the height!

    42. Invincibletro

      We know that heavier items fall faster due to their own gravity. Granted, it is such a small change, we don't use the measurement in most engineering calculations.

    43. Miriam Johnson

      So that was what Pipin was doing...

    44. 908 resell

      "dad, how tall is that building?" "lets find out." pulls out cliff timer "head on up there, son."

    45. Queen Celeste


    46. Robert Oblinsky

      Hey Mark, You dropped this | \/ 👑and🧪 please don’t tell me it’s acid

    47. Silas Duke

      Your app is fucked up

      1. Swamp Rat 1



      *Science only goes so far, then comes God*

      1. Arham Shahid


    49. amanda c.

      0:20 - Been stuck for minutes trying to figure out where the 16 came from. Turns out it's because he was using freedoms per bald eagle squared.

    50. kateland parker

      For all my metric fans out there, if you want to know the height in meters instead of feet, simply use d=4.9(t)^2 .You're welcome!

    51. Seth Willis


    52. Anime Potato

      “How bout that.”

    53. RADROX247 GAMING

      Thanks for the apo

    54. Irene Stephens

      I tried that when measuring the height of trees in a survey, sadly it took so long to complete it, because i was hospitalized for several weeks after each jump!

    55. Ryan Roberts

      He does cuss when properly agitated!

    56. Rilakkuma's cookie

      what happens if you use different force on the objects that fall?

    57. Tanner Henry

      2:05 Thanks for including Tanooki Mario! Doesn't seem like the other 2 objects though. Mario logic.

    58. IPhone gamer

      hey Mark, if you see this comment, can you put your app on Play Store please? (if you ask, I love doing video archeology sometime)

    59. Justine Kent Hernia

      Wait the weight?????

    60. Mason Clews


    61. Dishant Deepak

      Ruining UKuprs' lives since 2013

    62. Marco

      The only guy verifying cliff jumps

    63. Eelco Frans

      2014 nah2015 nah 2016 nah 2017 nah 2018 nah 2019 nah 2020 yes he waited enough

    64. Vada

      "How 'bout that!" -man of science in an extremely deadly enviornment.

    65. Melalaine Cobico

      2:54 Nice

    66. TheBlueBanananana

      True fact: you have no idea what he is saying half the time Also true: you click on his videos anyway

    67. Rok Krmelj

      start using metric system first.....

    68. Ayman J97

      nice voice over XDXDXD

    69. Nitroxitation

      3:35 Mark Rober sounded like he swore

    70. Avon Junior Primary

      you're the greatest nobody can defeat you

    71. Noelle Maynard Holmes


    72. Tom A

      Stop using cheap clickbaits and ancient units of measurement (or at least provide both), and I will subscribe to your channel again.

      1. Arham Shahid

        that'll scare him. whatever will he do without you.

    73. idontneedaname85

      0:01 you are welcome

    74. Benjamin Tran

      0:30 took not taked cmon rober

      1. AlphaChalices451

        You really got him there Benjamin Tran!

    75. Ella B

      My iPad didn’t like this audio 2:07

      1. AlphaChalices451


    76. Matthew Johnson

      I was thinking, "OK, 9.81 m/s^2 acceleration" and then you said "16" and I immediately was disappointed in you for not teaching your UKup fans to use standard SI measurements :)

      1. AlphaChalices451


    77. Flynn

      Only if I knew this when I went caving, then I would know how deep the endless pit is

    78. Quinn Moore

      Downloaded the app strait away

    79. digital Friday


    80. Sahil Sahebzada

      Bro on Christmas my wish is that I can be smart as him I wishhhhhhhhhhhhh

      1. AlphaChalices451

        Work for it. It isnt as much as how naturally talented you, its how much effort you put into your education. And its not a tell myself and I am, you have to put in the boring hours of learning if you want to succeed

    81. Moritz Lässer

      What is 48ft in an actual measurement?

      1. Aiden Huang

        209 and a half big macs

    82. Luke Duckworth

      Who watching this in 2020

      1. AlphaChalices451


    83. Harry Coupe

      He sounded so different

    84. OneHitWarrior1

      1:58 "how bout that" 😂😂😂

    85. Christopher Stewart

      I LOVE you Mark

    86. Jaco Ja

      But... But this video wasn't planned 8 months ago 🤦🏻‍♂️

    87. boudiemation

      americans am i right

      1. AlphaChalices451


    88. Biaka

      Nice learned something new today.👍

    89. Oasis Spida

      Me and my friend judged that the Empire State Building is 381 m tall. Rest In Peace terry

      1. AlphaChalices451

        Jab jab power dunk

    90. Universum

      The air resistance was not taken into account.

      1. AlphaChalices451

        Yes it is not 100 percent accurate. He acknowledge this

    91. Akiboiii

      me telling my friends i like to watch Mark Robers Videos They saying hes a nerd me saying that i dont care if hes a nerd (hes not) i just think its cool that hes so frickin smart.

      1. AlphaChalices451

        Being smart is an effort. Mark Rober has a ton of effort and passion in what he does

    92. Koliha Jonáš

      The apps told me that planes are in the space :O

    93. ian mafnas

      the time in youtube vidios are diffrent in real life

    94. Batbot2006

      But it depends on if they jump,fall or get accidentally-on purpose pushed off the cliff

      1. Batbot2006

        Biaka For ... science

      2. Biaka

        Why would you time someone who falls or accidentally on purpose pushed off the cliff, just to know the height.

    95. parmesian

      when you used imperial rather than metric, that hurt. nasa themselves lost a $125 million mars orbiter because they measured everything in imperial units but everyone else used metric. the us needs to convert to metric imo, it’s so much easier to understand

    96. A_bizarreboiz

      How did I learn this in like 7 seconds (Nobody thought me this till now)

    97. Maise cloudy Girl

      I’m only six years late

    98. Juan Motorsports

      Lol 61’ wawawawawaaaaahhhh

    99. Legendary Lime

      Now this is a new way to discover how high my skyscraper is.

    100. Productivity

      ew feet