Lecture 26: Elasticity - Young's Modulus

author: Walter H. G. Lewin, Center for Future Civic Media, Massachusetts Institute of Technology, MIT
recorded by: Massachusetts Institute of Technology, MIT
published: Oct. 10, 2008,   recorded: November 1999,   views: 35291
released under terms of: Creative Commons Attribution Non-Commercial Share Alike (CC-BY-NC-SA)

See Also:

Download Video - generic video source Download mit801f99_lewin_lec26_01.m4v (Video - generic video source 113.6 MB)

Download Video - generic video source Download mit801f99_lewin_lec26_01.rm (Video - generic video source 109.5 MB)

Download Video Download mit801f99_lewin_lec26_01.flv (Video 112.9 MB)

Download Video Download mit801f99_lewin_lec26_01_352x240_h264.mp4 (Video 150.3 MB)

Download Video Download mit801f99_lewin_lec26_01.wmv (Video 443.3 MB)

Download subtitles Download subtitles: TT/XML, RT, SRT

Help icon Streaming Video Help

Related Open Educational Resources

Related content

Report a problem or upload files

If you have found a problem with this lecture or would like to send us extra material, articles, exercises, etc., please use our ticket system to describe your request and upload the data.
Enter your e-mail into the 'Cc' field, and we will keep you updated with your request's status.
Lecture popularity: You need to login to cast your vote.



1. Elasticity of Materials:

A relationship between stress, strain and Young's Modulus is introduced by analogy with springs. The properties of various metals are compared, and the stress vs. strain curve is described.

2. Measuring Stress vs. Strain:

An apparatus for measuring very small elongations of a wire under stress is described. A set of measurements are made to construct the stress vs. strain curve for a copper wire. From these, both Young's modulus and the ultimate tensile strength can be calculated.

3. Spring Constant of a Wire:

At low stress values, where the stress vs. strain curve is linear, one can generate simple harmonic oscillations in the vertical direction by hanging an object from a wire.

4. Speed of Sound in Materials:

The speed of sound in a material depends on the stiffness (Young's modulus) and density of the material. The speed of sound and length of a rod determine the roundtrip time of a pressure disturbance introduced at one end. From this follows the fundamental frequency at which a rod resonates.

5. Demo with a 2 kg Block and Two Strings:

A 2 kg block is suspended from one string, and an identical string is suspended from the block. Professor Lewin pulls on the lower string. Which string will break first, the upper one or the lower one? The lower string will break first if the force is impulsive (a quick jerk) because it will elongate faster than the upper string. If we pull slowly the upper string will break first as its tension will then always exceed that of the lower string.

Link this page

Would you like to put a link to this lecture on your homepage?
Go ahead! Copy the HTML snippet !

Reviews and comments:

Comment1 Yash, April 18, 2010 at 6:41 a.m.:

very very thanks to Sir Lewin...regards and gratitude from India.

Comment2 liuwen , July 6, 2010 at 5:44 a.m.:

I can not understand english

Comment3 M.Prasad, September 21, 2010 at 6:46 a.m.:

very very thanks to Sir Lewin...regards and gratitude from India.

Comment4 Marcelo, April 1, 2011 at 2:20 a.m.:

Thank you so much for kind innitiative, I express grattitude from Brazil.

Comment5 M. Rao, March 2, 2012 at 6:46 a.m.:

Thank you so much, It is very intresting for me being attending in this kind of artifitial classes,
But I 'd like to have access to download some of lectures to use in my English classes for civil engineering students in our university. I am teaching in Iran
best regards
M. Rao

Comment6 arul, August 3, 2012 at 6:37 a.m.:

thank you so much , such kind of lecture very useful for me ,
when doing work with study.


Comment7 shubham, October 15, 2013 at 7:58 p.m.:

nice one ..... please put there more material related to civil engineering .... specially strength of materials and survey ....

Comment8 Davor form VideoLectures, December 18, 2017 at 10:33 a.m.:

Hi all!

We have translated this entire course for you from English into 11 languages.

Check this video and give us some feedback in this short survey https://www.surveymonkey.co.uk/r/6DMBC3Q

Write your own review or comment:

make sure you have javascript enabled or clear this field: