| Differences between revisions 12 and 13 | Back to page |
|
Size: 1024
Comment:
|
← Revision 13 as of 10:14PM, Oct 03, 2011 ⇥
Size: 735
Comment:
|
| Deletions are marked like this. | Additions are marked like this. |
| Line 20: | Line 20: |
= The work energy "theorem" = The work energy theorem, $\Delta T = W$ where $T$ is the kinetic energy (and $\Delta T = T_2 - T_1$ is its change) and $W$ is the net work done on the particle, is A. always valid (in classical mechanics). A. valid only for conservative forces. |
Which force?
Friction, air resistance, tension, spring force, normal force, etc. are all due to
- Gravitational interaction
- Electromagnetic interaction
- Strong interaction
- Weak interaction
Ans. A. An electromagentic interaction refers to the interaction of two electrically charged objects by exchanging photons.
The force is everywhere
When two objects exchange forces, they can do so without having to contact each other.
- Yes
- No
Ans. What do you mean by contact? Does exchanging photons or gravitons count as contact? On a more practical level, it is very helpful to remember, "no contact, no force except gravity," in most problems of classical mechanics.