1 / 11

Hookes Law

Hookes Law. Robert Hooke 1635-1703. Researched and wrote papers on Geometry, Snowflakes, Heat, Astronomy, Fossils, Air Pumps, Light, Watches, Telescopes and Silkworms…..among other things

tatianaj
Download Presentation

Hookes Law

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Hookes Law .

  2. Robert Hooke 1635-1703 • Researched and wrote papers on Geometry, Snowflakes, Heat, Astronomy, Fossils, Air Pumps, Light, Watches, Telescopes and Silkworms…..among other things • Continually squabbled with Newton with whom he was miffed because Newton seemed to get all the attention and credit..Hookes Law was one of the few things he was popularly credited with • A rather crabby individual but credited with the invention of universal joints, the balance wheel and the iris diaphragm

  3. What did Hooke discover ? • the more force that was put on materials the more they extended • With some materials they also extended in a regular way eg if the force was doubled so did the extension • this was true as long as their elastic limit was not exceeded

  4. What does this mean?

  5. What the graph shows

  6. What is the elastic limit? • The material no longer shows elastic behaviour (ie does not return to original size when stretching force is removed) • The material is permanently deformed ie is larger or longer than originally • The material is weaker as the above effects are caused by fracture of some atomic bonds

  7. Since Forceis proportional toextensionHookes Law could be put as Where F is the applied force in Newtons x is the extension in metres Or if k is the proportionality constant F=kx

  8. What does k mean in F=kx? • k is called the spring constant and is a measure of the stiffness of the spring or material • It has units of Nm-1 (newtons per metre) • The higher the k the stiffer the spring • Materials with a high k need a large force to for a given extension • adding springs in series or parallel changes k

  9. k decreases by 2 Combined springs slacken compared with single spring extension doubles Series and parallel springs Parallel Series k increases by 2 Combined springs stiffen compared with single spring extension halves

  10. So what? • Understanding Hookes law is critical to the construction of any structure eg bridges buildings • Deformation of materials is also critical in vehicle design though in practice the terms stress( the force per square metre) and strain (the extension per unit length) are more commonly used instead of simply force and extension • Get audience involvement.

  11. Summary: A material is said to obey Hookes Law if its extension is directly proportional to the applied force More info on Hooke at http://www.roberthooke.org.uk/

More Related