Smart stand-alone CD/DVD player?

stf92 · 07-26-2012, 10:32 PM

Hi:

I turn on my CD player (hardware, stand-alone) and begin to listen to the music. Then I press PAUSE. The motor goes on spinning. I come back after some hours and find, the player still paused, that the motor is stopped, that is, it's no longer spinning (I notice by putting my ear very close to the player). I press PLAY and the motor starts.

In fact, after some 60 secs of being paused, the motor halts. Are all CD players like mine?

dugan · 07-27-2012, 08:27 AM

Yes. It takes 60 seconds to stop spinning because of Newton's first law of motion.

stf92 · 07-27-2012, 11:30 AM

Quote:

Originally Posted by dugan

Yes. It takes 60 seconds to stop spinning because of Newton's first law of motion.

You mean that the effect of pausing the player is to remove the power to the motor? That is, there no longer is a voltage applied to the motor? Well then it is Newton's second law which applies, because if it was spinning and after 60 seconds it is at rest, then there has been an angular acceleration (negative acceleration) caused by friction.