1 / 17

PHYS16 – Lecture 17

PHYS16 – Lecture 17. Energy Conservation: Springs October 18, 2010. Review. Practice Question 1. If the momentum of an object increases by 4 fold, how much does the kinetic energy of the object change by? 1/16 ¼ 2 4 16. Practice Question 2.

coye
Download Presentation

PHYS16 – Lecture 17

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. PHYS16 – Lecture 17 Energy Conservation: Springs October 18, 2010

  2. Review

  3. Practice Question 1 • If the momentum of an object increases by 4 fold, how much does the kinetic energy of the object change by? • 1/16 • ¼ • 2 • 4 • 16

  4. Practice Question 2 • If the potential energy of a 5 kg book is 100 J, what is the height of the book? • 2 m • 1 m • 20 m • 10 m • There is not enough information

  5. Practice Question 3 • If a car engine for a 1400 kg car outputs 1000 kW of average power, how much time does it take to accelerate from 0 to 25 m/s? • 0.4 s • 1 s • 0.2 s • 0.8 s • 10 s

  6. This Week • Spring Force and Energy • Conservative vs. Nonconservative Forces • Conservation of Energy • Sleds and Rollercoasters • Springs • Pendulums

  7. Springs

  8. Spring Force and Energy • Spring Force • Spring Energy http://ux1.eiu.edu

  9. What is the Energy of this system? Assume x=0 at Equilibrium point then… http://sparknotes.com

  10. What is the Energy of this system? Approach #1 Assume x=0 at Equilibrium point then… Approach #2 Assume x=0 at ground then… http://sparknotes.com Accounting for zero point not at equilibrium

  11. Zero of Potential Energy • Wherever you set your zero point for potential energy will determine your coordinate system • U=0 J at y=0 point for gravitational pot. energy • U=0 J at equilibrium point for spring pot. Energy • All calculations of ΔU will be relative so it won’t matter where you put 0 J just make sure not to switch back and forth!!!

  12. Energy Conservation

  13. Conservative vs. Nonconservative Forces • Conservative Forces– force where work done over ANY closed path is zero WAtoB= -WBtoA WAtoB, path 1 = WAtoB, path 2 • Nonconservative force – not conservative

  14. Is Gravity a conservative Force? • Let’s assume two different paths and see if we get the same work… Path #1 Path #2 Yes, so gravity is conservative!

  15. Is the spring force conservative? • Let’s assume two different paths and see if we get the same work… Path #1 Path #2 Yes, so spring force is conservative!

  16. Is friction conservative? • Let’s assume two different paths and see if we get the same work… Path #1 Ff Ff Path #2 Ff No, so friction is nonconservative…

  17. Conservative vs. Nonconservative Forces • Conservative • Spring Force • Gravity • Buoyant Force • Nonconservative • Friction • Air resistance/Drag • Fluid resistance • Applied Forces Situation Dependent Tension Normal Force

More Related