Analyzing the Apollo 15 Feather and Hammer Drop - A Basic, Introductory Free-Fall Problem

Apollo 15 Video Courtesy of NASA: The 1971 Feather and Hammer Drop Experiment performed by Astronaut David Scott. We analyze the experiment to determine the height from which the feather and hammer were dropped. It is a great, basic, introductory free-fall problem.

0:00 Intro
0:19 Why the experiment was done.
0:32 Let's enjoy the video
1:27 Beginning to analyze the video
2:23 Using the Frame Rate
3:00 Counting the frames
3:50 Solving for the initial height
4:51 The answer to how high the feather and hammer were dropped
5:31 The Review

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Introduction to Free-Fall and the Acceleration due to Gravity

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Dropping a Ball from 2.0 Meters - An Introductory Free-Fall Acceleration Problem

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Picture of Astronaut David Scott and Apollo 15 video: This file is in the public domain because it was solely created by NASA. NASA copyright policy states that "NASA material is not protected by copyright unless noted".

Apollos 15 Video:

[monteiro]

Amazing video. I was 9 years old at the time and still remember. Thanks Professor, awesome job.👍👍

[peatmoss]

This one tiny video proves it was done on the moon, that is why there are no moon "lunatic deniers" on the page. Which is a bummer because I love reading their out of this world explanations!

[wellesmorgado]

One of the most interesting aspects of a Moon film, that people rarely notice, is the absence of dust! At the end of the hammer + feather video, the astronaut shuffles his feet around and kicks a lot of dirt but there is no cloud of dust. No air, no dust. Dust is a suspension of very small grains on the air.

[agerven]

Great learning.
Remember having seen this video live at the time, thanks to my dad. And guess what, I got to study physics! Great learning with this video, thanks for that.

[karlfridrik]

Flippin physics.. love those mathematic skills and explanation.. how ever i am skeptic about the apollo bs. Sowy.

But keep those videos rolling, you are in your zone there. 👍👌

Thanks.

[saadzubair]

love your teaching method, and i have same questions that your student asks from you.lots of love from pakistan.
keep it up sir.

[moviephysics]

It could have been more fun to estimate the height and time from the clip to find g(moon) and then use that to estimate the mass of the moon?

[rvsamsung]

David Scott's height is 1.83m. And he drops it from the height of his chest which is 1.45-1.6m. But the calculated dropheight is only 1.2m... the explanation of this could be the camera on the moon only had a frame rate of 24 fps...

[criztu]

The "feather" bounces back in the air after hitting the ground at 1:20. Are you sane enough to see the truth?

[stardustypsyche]

Actually acceleration due to gravity is not independent of mass, but the mass of a planet (moon) is so much greater than either the hammer or the feather that the difference is below the resolution of a simple visual experiment, yet calculable.






F
=
G




m

1



m

2




r

2




 


{\displaystyle F=G{\frac {m_{1}m_{2}}{r^{2}}}\ }

Then calculate the acceleration of each body with a=F/m

[markyounger]

If you want to get REALLY technical. The drop is not totally on the Y axis due to tidal difference as his arms were laterally displaced

[mrvanderhorst]

Excellent!  The explanation is clear, the equations are used very well (good notation), and it is very interesting!  Thanks for sharing!

[dks]

I well remember Dave Scott doing that Hadley Rille.

[chauphan]

Is the acceleration due to gravity on y-axis always negative 9.8 m/s^2? What is the acceleration when we throw a ball up before it goes back down ?

[FlyBoyGrounded]

1.2 metres doesn't seem high enough to me. David Scott is 6ft tall and he's dropping from nearly shoulder height. You show where 1.2 metres come up to on you but how tall are you?

[hk]

Saying delta-t is 1.201201s is bad. You imply you measured the freefall time with an accuracy of one millionth second, which is far from the real thing. At best, you could determine the time by +/- one or two frames. With the knowledge of all the inaccuracies, you would simple divide 36/30 to get 1.2 seconds without any calculators and go on with this value.

[coach]

Hey professor, why does the feather bounce (as asked by someone else in the comments)? Frame rate issue, or a moon thing or because it's a falcon feather which has a different buoyancy than other birds....

[hulkflattt]

if you do a test at home with a falcon feather and hammer you will get the same results

[spinfowars]

the easiest way I can think of to prove that they were in a vacuum on the moon would have been to take a plain piece of paper and show that it is thin and flexible by waving it showing that it bends - then hold it at the top and let it hang straight down - then let it go -
[
if there were no atmosphere then the paper would fall straight down without fluttering to the side at all
[
that test would have been so easy - they did not do that though
]
if there were any atmosphere - then the paper would flutter to the side and then continue to flutter to the ground
[
they could have also flipped the paper - rotating axially against the flat face - and it would continue rotating in a vacuum, but in atmosphere it would rapidly slow down and stop and change rotation
]

[bitukukuasukgremany]

If you speed the moon vid's up they move like people on Earth so this vid is half speed like the others right?