10-01-PotentialEnergy

# 10-01-PotentialEnergy - Chapter 8 Potential Energy and...

This preview shows pages 1–4. Sign up to view the full content.

1 Work done by gravity 0 90 cos o d Weight (a) If the object moves horizontally , d Weight o 90 cos Fd W d Weight Weight Weight o 180 d (b) If the object moves upward , 1 180 cos o d Weight Weight Weight o 0 d 1 0 cos o (c)If the object moves downward , gravity does NO work. gravity does Negative work. gravity does positive work. Chapter 8 Potential Energy and Conservation of Energy mgd Work mgd Work Work done by the gravitational force mgd W B gravityA The work depends only on the difference between the initial height h A and the final height h B . It does not depend on the path from A to B ! d = h B -h A When an object of mass m moves from point A to point B near the surface of the Earth, the work done by the gravity is ) ( ) ( B A A B h h mg h h mg If the object follows the zigzag path from point A to point B, mgd W B gravityA d = h B -h A no no no no no + ) ( ) ( B A A B h h mg h h mg the work done by the gravity is still

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
2 The work done by gravity on a closed path is zero On a closed path A B C D A, mgh mgh W A D C B gravityA 0 ) ( 0 0 The concept of “Conservative Force” 1. A force is conservative when the work it does on an object moving from A to B is independent of the path between A and B. Or 2. A force is conservative when the work it does on an object moving along any closed path is zero. Conservative forces Gravity Spring forces Non-Conservative forces Friction Muscular forces A B path1 path2 W 1 =W 2 A W=0
3 The work done by friction on a closed path is different

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 7

10-01-PotentialEnergy - Chapter 8 Potential Energy and...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online